Using Podman

Podman is a daemonless alternative to Docker, which is mostly compatible with Docker containers.

Creating a systemd service file

Podman is easier to run in systemd than Docker due to its daemonless architechture. It comes with a handy generate systemd command which can generate systemd files. Here is a good article that goes into more detail as well as this article detailing some more recent updates.

$ podman run -d --name vaultwarden -v /vw-data/:/data/:Z -e ROCKET_PORT=8080 -p 8080:8080 vaultwarden/server:latest
54502f309f3092d32b4c496ef3d099b270b2af7b5464e7cb4887bc16a4d38597
$ podman generate systemd --name vaultwarden
# container-vaultwarden.service
# autogenerated by Podman 1.6.2
# Tue Nov 19 15:49:15 CET 2019

[Unit]
Description=Podman container-vaultwarden.service
Documentation=man:podman-generate-systemd(1)

[Service]
Restart=on-failure
ExecStart=/usr/bin/podman start vaultwarden
ExecStop=/usr/bin/podman stop -t 10 vaultwarden
KillMode=none
Type=forking
PIDFile=/run/user/1000/overlay-containers/54502f309f3092d32b4c496ef3d099b270b2af7b5464e7cb4887bc16a4d38597/userdata/conmon.pid

[Install]
WantedBy=multi-user.target default.target

You can provide a --files flag to tell podman to put the systemd service into a file or use podman generate systemd --name vaultwarden > /etc/systemd/system/container-vaultwarden.service. With this we can enable and start the container as any normal service file.

$ systemctl enable /etc/systemd/system/container-vaultwarden.service
$ systemctl start container-vaultwarden.service

New container every restart

If we want to create a new container every time the service starts we can use the podman generate systemd --new command to generate a service file that recreates containers

$ podman generate systemd --new --name vaultwarden

If you're using an older Podman, you can edit the service file to contain the following instead:

[Unit]
Description=Podman container-vaultwarden.service

[Service]
Restart=on-failure
ExecStartPre=/usr/bin/rm -f /%t/%n-pid /%t/%n-cid
ExecStart=/usr/bin/podman run --conmon-pidfile /%t/%n-pid --cidfile /%t/%n-cid --env-file=/home/spytec/Vaultwarden/vaultwarden.conf -d -p 8080:8080 -v /home/spytec/Vaultwarden/vw-data:/data/:Z vaultwarden/server:latest
ExecStop=/usr/bin/podman stop -t "15" --cidfile /%t/%n-cid
ExecStop=/usr/bin/podman rm -f --cidfile /%t/%n-cid
KillMode=none
Type=forking
PIDFile=/%t/%n-pid

[Install]
WantedBy=multi-user.target default.target

Where vaultwarden.conf environment file can contain all the container environment values you need

ROCKET_PORT=8080

If you want the container to have a specific name, you might need to add ExecStartPre=/usr/bin/podman rm -i -f vaultwarden if the process isn't cleaned up correctly. Note that this method currently doesn't work with the User= options users (see https://github.com/containers/podman/issues/5572).

Troubleshooting

Debugging systemd service file

If the host goes down or the container crashes, the systemd service file should automatically stop the existing container and spin it up again. We can find the error through journalctl -u container-vaultwarden -t 100.

Most of the time the errors we see can be fixed by simply upping the timeout in Podman command in the service file.