Tips and tricks 📚 + 🔍 = 💡

Git

empty directory (.gitignore + .gitkeep combo)

Add (before the ! line) any empty directories you want to commit which contains a .gitkeep files.

Exemple: keep a data directory in your repo

/data/*
!/**/.gitkeep

Linux

Dbus error when calling systemctl --user

This will happen when libpam-systemd package is not installed.

Should be installed by default with dbus-session-user package in latest Debian-based distributions.

Unbound

wildcard *.docker.localhost

💡 This minimal configuration is handy to target Traefik containers by their generated hostnames.

In /etc/unbound/unbound.conf.d/docker.localhost.conf :

local-zone: "docker.localhost." redirect
local-data: "docker.localhost IN A 127.0.0.1"

Traefik.io

get Docker containers registered in Traefik (API) :

$ curl -s "http://localhost:8080/api" | \
  jq '.docker | .frontends | .[] | .routes | .[] | .rule | split(":")[1]'

Saltstack

states order matters :

In top.sls (or included sls within a state), the order of states will be processed in the declared order :

 - "role:webserver":
    - apache
    - php-fpm
    - other_packages

The webserver role will apply its states in the following order:

1. apache.sls
2. php-fpm.sls
3. other_packages.sls

Docker

Cleanup images and containers

1. Remove containers that are not running anymore:

docker ps -q -a -f=status={created,exited,dead} | xargs --no-run-if-empty docker rm

2. Remove unused images

docker images -f=dangling=true -q | xargs --no-run-if-empty docker rmi

fix bind mounts permissions with userns-remap

/etc/docker/daemon.json

{
  "userns-remap": "USER"
}

/etc/subuid

USER:1000:1
USER:100000:65536

/etc/subgid

USER:<docker_group>:1
USER:100000:65536

Replace USER with your user login and <docker_group> with GID of docker (usefull in order to allow some container to access docker.socket)

Restart your docker daemon and you will see future bind mounted volumes owned by your user 😜.

SSH

Proxy HTTP(S) to remote host via SOCKS5

ssh -D localhost:8080 <user>@<remote-host>

Then setup your browser's proxy extension with a SOCK5 proxy pointing at localhost:8080

SystemD

Completely override ExecStart service with drop-in configuration

Put an override.conf file in the corresponding <service>.d (eg. /etc/systemd/user/amazing.service.d):

[Service]
ExecStart=
ExecStart=/bin/true

.env (dotenv)

Load .env in shell

export $(grep -Ev '^#' ./.env | xargs );

Rsync

get changes in dry-run

every time, I forget about the -i, --itemize-changes option …

$ rsync -n -i -aP <source> <destination>