How to Schedule Tasks with Cron and systemd Timers

Automating routine tasks is a core strength of Linux systems. Two popular ways to schedule recurring jobs are cron and systemd timers. While cron has been a staple for decades, systemd timers offer more flexibility and are better integrated into modern Linux systems. In this post, we’ll look at how to use both to automate tasks.

Using Cron for Task Scheduling

1. What is Cron?

cron is a time-based job scheduler in Unix-like operating systems. It allows users to run scripts or commands at scheduled times or intervals.

2. Create a Cron Job

To edit your crontab:

crontab -e

A cron job follows this format:

* * * * * /path/to/command

Fields:

┌───────────── minute (0 - 59)
│ ┌───────────── hour (0 - 23)
│ │ ┌───────────── day of the month (1 - 31)
│ │ │ ┌───────────── month (1 - 12)
│ │ │ │ ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
│ │ │ │ │
* * * * * command to execute

Example:
Run a backup script every day at 2 AM:

0 2 * * * /home/user/scripts/backup.sh

Using systemd Timers

1. Why systemd Timers?

Unlike cron, systemd timers integrate with the systemd init system. They allow for logging, dependency management, and more powerful scheduling options.

2. Create a systemd Service and Timer

Step 1: Create a Service File

Create /etc/systemd/system/backup.service:

[Unit]
Description=Run Backup Script

[Service]
Type=oneshot
ExecStart=/home/user/scripts/backup.sh

Step 2: Create a Timer File

Create /etc/systemd/system/backup.timer:

[Unit]
Description=Daily Backup Timer

[Timer]
OnCalendar=daily
Persistent=true

[Install]
WantedBy=timers.target

Step 3: Enable and Start the Timer

sudo systemctl daemon-reexec
sudo systemctl enable --now backup.timer

Check the status:

systemctl list-timers

When to Use What?

Use cron for simplicity and widespread availability, but prefer systemd timers for better control and system integration.

How to Schedule Tasks with Cron and systemd Timers (F.A.Q)