systemd service fails after pacman upgrade but journalctl shows no error output

Answer first

The service is in a failed state but journalctl -u shows no visible messages because the failure occurs before the unit’s stdout/stderr is attached to the journal, or the log is being filtered by boot scope and user access. With Storage=persistent set, the journal can still be empty for this unit if the failure is an early exec failure, ExecStartPre exit, or a missing binary/library that prevents the process from spawning.

Confirmed facts vs likely explanation

Confirmed: Unit was enabled and running pre-upgrade. Pacman transaction log confirms updates. Journal persistence is configured and retention covers the failure window. Non-root journal access is granted via systemd-journal group.

Likely explanation, not confirmed: ExecStartPre failure, binary incompatibility from a library update, or a missing dependency causing immediate exec failure. These conditions can leave systemd in failed state with no journal entries for the unit’s main process.

Steps needed for this case

1. Confirm current state and timestamp

systemctl status <unit-name>.service --no-pager
journalctl -b -u <unit-name>.service --no-pager

Use -b to include boot-time logs. -u alone can miss messages from early transitions.

2. Correlate failure time with pacman

systemctl show -p ActiveEnterTimestamp --value <unit-name>.service
journalctl --since "5 minutes ago" --until "now" -u <unit-name>.service
grep -i "upgraded\|installed" /var/log/pacman.log | tail -n 200

Match the failure timestamp from systemctl status with the last pacman transaction entries.

3. Check ExecStartPre and ExecStart paths

systemctl cat <unit-name>.service

Note the ExecStartPre and ExecStart commands and the User= setting.

4. Verify binary and library dependencies

which <binary-from-ExecStart>
ldd $(which <binary>)

Look for missing or incompatible shared libraries after the upgrade.

5. Manual execution test

sudo -u <service-user> <full-path-to-binary> --help

Run the binary as the service user to see direct error output that systemd may not capture.

One missing diagnostic detail that changes the recommendation: the exact unit name and the ExecStart/ExecStartPre lines from systemctl cat. Without them the ldd and manual exec checks cannot be scoped safely.