cron — cron jobs

Upgrades remove or move programs — old Python versions are the classic case — and a cron job calling one fails silently every time it runs.

At a glance

ID	cron
Category	Services
Needs root	no
Needs programs	none
Compares with a snapshot	yes
Options	0

What it checks

• System crontabs (/etc/crontab, /etc/cron.d/*) and, as root, user crontabs (/var/spool/cron/crontabs/*).
• For each job, whether the program it runs (an absolute path) exists. Jobs that guard themselves with test -x PROGRAM && or [ -x PROGRAM ] && are left out, since they're written to cope.
• Whether a cron daemon (cron, cronie or crond) is running when there are jobs.

Findings

Severity	Finding	What to do
warning	N cron jobs run programs that don't exist	Find what provided the program (dpkg -S, apt-file search); install the replacement and update the job, or remove it.
warning	No cron daemon is running	sudo apt install cron && sudo systemctl enable --now cron.
info	N cron jobs were removed by the upgrade	Package-provided jobs come and go with their packages; check none of yours is among them.

Compared with a snapshot

The snapshot records every job (file, schedule, command).

Commands it runs

systemctl list-units --type=service --state=active --no-legend --plain --no-pager

To see which cron daemon runs; skipped without systemd.

Limitations

• Only absolute program paths are checked; commands found through PATH aren't.
• Without root, user crontabs aren't read.
• systemd timers are covered by systemd-timers.

Options

This check has no options. Turn it off with enabled: false under checks: cron: in the configuration file, or for one run with --skip cron.