anacron

Run periodic jobs on systems not running continuously

TLDR

Run anacron jobs now

$ sudo anacron -n

Run in foreground

$ sudo anacron -d

Test run (don't execute jobs)

$ anacron -T

Force run regardless of timestamps

$ sudo anacron -f

Use specific config file

$ sudo anacron -t [/etc/anacrontab]

SYNOPSIS

anacron [-s] [-f] [-n] [-d] [-t anacrontab] [-T]

anacron is a cron-like job scheduler that doesn't assume the computer is running continuously. It's ideal for laptops and desktop machines that aren't powered on 24/7, ensuring periodic jobs run even if the scheduled time was missed.Unlike cron, which runs jobs at specific times, anacron runs jobs based on periods (daily, weekly, monthly) and tracks the last run date. If a job's period has elapsed since the last run, it executes the job.

PARAMETERS

-f

Force execution ignoring timestamps

-n

Run jobs now, ignoring delays

-d

Run in foreground (no daemon)

-s

Serialize job execution (sequential)

-T

Test configuration file syntax only

-t file

Use alternate anacrontab file

-S dir

Use alternate spool directory

-u

Update timestamps only, don't run jobs

CONFIGURATION

/etc/anacrontab

Defines periodic jobs with their period in days, delay in minutes, identifier, and command to execute.

/var/spool/anacron/

Timestamp files tracking the last execution date of each job.

INSTALL

sudo apt install anacron

sudo dnf install cronie

sudo pacman -S cronie

sudo apk add cronie

sudo zypper install cronie

nix profile install nixpkgs#cronie

CAVEATS

Runs as root by default; user-level jobs require additional configuration. Job delay settings are randomized to avoid resource spikes. Not suitable for time-critical tasks.

HISTORY

anacron was created by Christian Schwarz and first released in 1998 to address cron's unsuitability for machines that aren't always on. Most modern Linux distributions include it alongside traditional cron.