Using Podman Quadlets

Sources used: podman docs

Intro

Podman Quadlet is a Podman/systemd feature that allows you to easily create and start containers on boot.
A very basic Quadlet for Syncthing has been given below, as example is the best way to understand anything.

Creating a Quadlet file

Where to put stuff

For a rootless Quadlet (recommended), create a file under…

• /etc/containers/systemd/users/ (All users)
• ~/.config/containers/systemd/ (Your user)

with any of the following filename extensions…

• .container
• .volume
• .network
• .build
• .pod
• .kube
• .artifact

e.g. for our purposes, we will create the file as follows: ~/.config/containers/systemd/syncthing.container

Basic Syntax

For our newly created syncthing.container file, we will put the following:

# syncthing.container
[Unit]
Description=Syncthing Quadlet (User)

[Container]
Image=docker.io/syncthing/syncthing

# Equivalent to: --network host
Network=host

# Equivalent to: --security-opt label=disable
SecurityLabelDisable=yes

# Environment variables
Environment=PUID=0
Environment=PGID=0
Environment=STHOMEDIR=/var/syncthing/.local/state/syncthing

# Volumes
Volume=./%h/:/var/syncthing

[Install]
WantedBy=default.target

This is a Quadlet file that roughly corresponds to the following podman command:

podman create docker.io/syncthing/syncthing \
        --network host \
        --security-opt label=disable \
        -e PUID=0 -e PGID=0 \
        -e STHOMEDIR="/var/syncthing/.local/state/syncthing" \
        -v "$HOME:/var/syncthing"

After this, we must run systemctl daemon-reload --user so that the podman quadlet systemd generator can generate the necessary systemd .service file.

Listing Quadlets

You can list your current Quadlets by running the following:

❯ podman quadlet list
NAME                 UNIT NAME          PATH ON DISK                                                          STATUS         APPLICATION
syncthing.container  syncthing.service  /var/home/faeizmahrus/.config/containers/systemd/syncthing.container  inactive/dead  

Fixing errors

IF the STATUS field shows Not loaded, it means the podman quadlet systemd generator couldn’t generate a systemd .service file, most likely due to an issue with the Quadlet file’s syntax, given everything else is configured correctly.
To find out the error, run the following:

## To list errors and the generated .service file for all Quadlets
/usr/lib/systemd/system-generators/podman-system-generator --user --dryrun

## To list only the errors for a single Quadlet
systemd-analyze verify --user --generators=true syncthing.service

Starting the Quadlet

To enable the Quadlet, simply enable the generated systemd .service file.

systemctl enable --user --now syncthing.service

Optionally, enable linger for your user so the container stays running even when your user is logged out.

loginctl enable-linger $USER