Check if Reboot is Required on Linux

Here are some ways to determine if your Linux system requires a reboot following an updated.

RedHat OS Family

Applies to RedHat, CentOS, and Amazon-Linux.

Install the yum-utils package, which contains the command needs-restarting. This command can be used to check if a full reboot is required because of kernel or core library updates (using the -r option) or what services need restarting (using the -s option). The command returns a 0 if a reboot is not required, or a 1 if it is, so it can be scripted.

$ sudo needs-restarting -r
Updating Subscription Management repositories.
Core libraries or services have been updated since boot-up:
  * kernel
  * systemd

Reboot is required to fully utilize these updates.
More information: https://access.redhat.com/solutions/27943

Debian OS Family

Applies to Debian and Ubuntu.

If the file /var/run/reboot-required exists then the system needs a reboot. This script example shows how this can be checked.

#!/bin/bash
if [ -f /var/run/reboot-required  ]; then
  echo 'reboot required'
fi

A list of packages with pending changes that require a restart are listed in /var/run/reboot-required.pks

$ sudo cat /var/run/reboot-required.pkgs
libssl1.0.0

There is a helper tool for Debian/Ubuntu called needsrestart that can be installed.

sudo apt install needsrestart

Running this program with not options specified, will attempt to restart all services that have been updated. It can also be run interactively to see which services require restarts.

sudo needsrestart -r i