Automatically Update Arch Linux with Systemd

Automatically update Arch Linux packages if the updates are available. It is important to keep the packages up-to-date to provide an improvement including security fixes, stability, performance, features, and more.

To keep the installed packages up-to-date, we can create Systemd service and timer scheduler to automatically check and update available packages. It help to protect against zero-day attacks and vulnerabilities.

Information: During the upgrade process, the autoupdate.service below can't automatically resolve package conflict, it will skip or cancel the update process if a conflict is detected.

To resolve package conflict, run "pacman -Syu" command manually.

Create autoupdate service

Create a systemd service (autoupdate.service) using a text editor such as nano:

sudo nano /etc/systemd/system/autoupdate.service

Add following to the autoupdate.service:

[Unit]
 Description=Automatic Update
 After=network-online.target 

[Service]
 Type=simple
 ExecStart=/usr/bin/pacman -Syuq --noconfirm
 TimeoutStopSec=180
 KillMode=process
 KillSignal=SIGINT

[Install]
 WantedBy=multi-user.target

The autoupdate.service (autoupdate timer's dependency unit) require the network is up.

On service stop, systemd autoupdate.service will send an interrupt signal (SIGINT) then wait the process (pacman) to stop or complete the update process, after 180 seconds (timeout) systemd.kill will force terminate process using SIGTERM signal.

While installing a package, pacman will not immediately end the process after receive the interrupt signal (SIGINT), instead, pacman will continue upgrading the package until complete, then quit the process to avoid the package to be broken or corrupted.

Create autoupdate timer

Create a systemd timer (autoupdate.timer) using a text editor such as nano, to run the automatic updates service periodically (e.g. every 45 minutes):

sudo nano /etc/systemd/system/autoupdate.timer

Add following to the autoupdate.timer:

[Unit]
 Description=Automatic Update when booted up after 5 minutes then check the system for updates every 60 minutes

[Timer]
 OnBootSec=5min
 OnUnitActiveSec=60min
 Unit=autoupdate.service

[Install]
 WantedBy=multi-user.target

Enable the autoupdate.timer to automatically run at startup:

sudo systemctl enable /etc/systemd/system/autoupdate.timer

Troubleshooting

Package was broken and corrupted after interrupted install/update

If the automatic update were running when installing a package but interrupted by power failure or system crash, then you receive an error when running pacman (e.g. error: target not found: package name). 

Try to force reinstall the broken/corrupted package, then uninstall the package using the following commands:

sudo pacman -S --force package && sudo pacman -R package

If you're encountered a file issue conflict while upgrading package i.e "package: /path/file/ exists in filesystem" you can force pacman to upgrade the package:

sudo pacman -Syu --force

Note: Use the "--force" command to force package to be removed or upgraded, but use carefully. If the above steps doesn't work you can try another method from ArchWiki pacman's guide

References

1. pacman - ArchWiki
2. systemd - ArchWiki
3. Image by dxiri / CC-BY 2.0