devops linux terminal

After installing certain updates — especially kernel or system-level updates — your Linux server may require a reboot to apply changes fully. Ubuntu and Debian-based systems make it easy to check if a reboot is needed.

Check if a Reboot is Required

Simply check if the /var/run/reboot-required file exists. You can do this using the cat command:

cat /var/run/reboot-required

Example output:

*** System restart required ***

If the file exists, it means the system needs to be rebooted.

See Which Packages Triggered the Reboot

To find out which packages caused the reboot requirement, check the contents of /var/run/reboot-required.pkgs:

cat /var/run/reboot-required.pkgs

Example output on Debian 11:

linux-image-5.10.0-23-amd64
linux-image-5.10.0-23-cloud-amd64

This list shows which installed packages require a system restart — typically a new Linux kernel or related components.

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