Run a job every 5 minutes with a systemd timer (the cron replacement)

A systemd timer is two units that share a name: a .service that does the work, and a .timer that triggers it on a schedule. You enable the timer. This replaces */5 * * * * in cron, with proper logging and systemctl list-timers.

1. The service (the work)

Save as /etc/systemd/system/backup-sync.service:

[Unit]
Description=Sync backups to remote

[Service]
Type=oneshot
ExecStart=/usr/local/bin/backup-sync.sh

A timer-driven service is Type=oneshot and has no [Install] section — the timer starts it, so it must not be enabled on its own.

2. The timer (the schedule)

Save as /etc/systemd/system/backup-sync.timer (same base name):

[Unit]
Description=Run backup-sync every 5 minutes

[Timer]
OnCalendar=*:0/5
Persistent=true

[Install]
WantedBy=timers.target

• OnCalendar=*:0/5 means “every hour, at minutes 0, 5, 10, … 55” — i.e. every 5 minutes.
• Persistent=true runs the job once on boot if its scheduled time was missed while the machine was off (cron’s @reboot catch-up done right).
• Because the timer’s base name matches the service, no Unit= line is needed.

Enable the timer

sudo systemctl daemon-reload
sudo systemctl enable --now backup-sync.timer

Verify and inspect

systemctl list-timers backup-sync.timer    # next & last run
systemctl status backup-sync.service       # last result
journalctl -u backup-sync.service -f       # output of each run
sudo systemctl start backup-sync.service   # run it once, right now

Validate OnCalendar before trusting it: systemd-analyze calendar '*:0/5' prints the next elapses. Gotchas: enable the .timer, never the .service. If runs can overlap or stampede across many hosts, add RandomizedDelaySec= (see the randomized-timer recipe).