Linux – Auto-Reboot and Shutdown with Cron Jobs – Task Scheduler alternative How to configure a daily or weekly automatic shutdown & reboot of your machine using cron job in Linux CentOS, Ubuntu, Debian, RHEL

Since we just published a guide to setup an auto-reboot or auto-shutdown on Windows machines, we thought that it could be useful to do the same for Linux systems as well.

The Linux built-in counterpart of the Windows Task Scheduler is called cron and it’s available on all the major distributions – CentOS, Ubuntu, Debian, RHEL and so on. As we can expect from Linux, instead of the fancy GUI provided by Windows we can set up our tasks with a simple and practical configuration file – which you will find in the following path:

The great thing about the crontab file is that it contains an awesome comment-based tutorial which will instruct you on everything at a glance:

As we can see from the last line of the above code snippet, we did setup a system auto-reboot on every sunday at 00:00 AM (midnight) using the /sbin/shutdown command, which is the exact counterpart of the Windows shutdown.exe tool.

Cron web-based GUI

If you’re looking for a fancier way of doing things, you can also setup your cron jobs with crontab.guru, a great web-based tool that allows to do that with a nice graphical interface. This tool can be very useful for beginners because it auto-calculates the timing options and translates them in a human-readable way, thus avoiding unwanted errors. Cron job failures can be disastrous, the website says in a tagline right below the GUI, and it’s definitely right!

Troubleshooting

Cron jobs are great, but they come with a minor flaw that can make the life hard for Linux newcomers: the cron service runs off the hardware clock rather than system clock, which can lead to minor or major disasters depending on your configuration and time zone settings, such as:

• Cron jobs running at incorrect time, usually UTC instead of your local timezone.
• Cron jobs running each and every minute – an edge-case scenario which happend to me some weeks ago, which I’ll describe in another post.

… And so on.

If you are experiencing this, check out your hardware clock by typing hwclock, then your system clock by typing date: if they do differ, you definitely have an out-of-sync issue which you should properly address.

The best thing you can do to fix that is to synchronize your hardware clock with your system clock using the following command:

Or, alternatively:

Not bad, right? However, since such sync might go away during time, it could be even better to periodically perform a resync. Ironically, the best thing to do that is using cron itself!

Here’s a crontab file that synchronizes the hardware clock with the system clock each day at midnight and performs a reboot at 00:01 am each sunday:

Conclusion

That’s it for now: I hope that this small tutorial will help other System Administrator looking for a way to setup an automatic shutdown and/or reboot on Linux. In case you need to do the same on Windows machines, check up this post!

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