For anyone who's ever maintained a linux server, you know that updates are easy, but after almost every one, it says:

*** System restart required ***

I started wondering if rebooting was really required, since sometimes you have mission-critical or otherwise busy servers, and rebooting is going to cause a problem for your users.  But-- what if you need to reboot due to a security update or something like that?

Luckily, I found a simple shell script written by "Anton Lugovoi", which looks through your updates and classifies the need to restart as either low, medium, high, emergency, or critical.

I named the script reboot_required_check.sh and simply placed it in my home directory.

Note, you'll need to run as root.

#!/bin/bash
##################################
# Zabbix monitoring script
#
# Checking urgency in changelog
# for updates which require system restart
#
##################################
# Contact:
#  anton dot lugovoi at yandex dot ru
##################################
# ChangeLog:
#  20151205    initial creation
#  20151208    check uniq packages only
##################################

echo "Checking how urgent a reboot is needed (takes up to 10 sec to run)..."

    if [ -f /var/run/reboot-required.pkgs ]; then
      while read pkg; do
        tmp=`/usr/bin/apt-get changelog $pkg | \
             /bin/grep -m1 -ioP '(?<=[Uu]rgency[=:])(low|medium|high|emergency|critical)' | \
             tr '[:upper:]' '[:lower:]'`
        if [ -n $tmp ]; then
          if   [ "$tmp" == "low" ] && \
               [ "$urgency" != "medium" ] && \
               [ "$urgency" != "high" ] && \
               [ "$urgency" != "emergency" ] && \
               [ "$urgency" != "critical" ]; then
            urgency=low
          elif [ "$tmp" == "medium" ] && \
               [ "$urgency" != "high" ] && \
               [ "$urgency" != "emergency" ] && \
               [ "$urgency" != "critical" ]; then
            urgency=medium
          elif [ "$tmp" == "high" ] && \
               [ "$urgency" != "emergency" ] && \
               [ "$urgency" != "critical" ]; then
            urgency=high
          elif [ "$tmp" == "emergency" ] && \
               [ "$urgency" != "critical" ]; then
            urgency=emergency
          elif [ "$tmp" == "critical" ]; then
            urgency=critical
            break
          fi
        fi
      done < <(sort -u /run/reboot-required.pkgs)
    else
      urgency=none
    fi

    case "$urgency" in
        none)      urgency='none' ;;
        low)       urgency='low' ;;
        medium)    urgency='medium' ;;
        high)      urgency='high' ;;
        emergency) urgency='emergency' ;;
        critical)  urgency='critical' ;;
        *)         urgency='asterisk?' ;;
    esac

echo ""
echo "   Reboot urgency = $urgency"
echo ""
echo " ('none', 'low', or 'medium' you probably do not need to reboot)"
echo ""
exit 0

Chmod the file so you can execute it:

chmod 755 reboot_required_check.sh    (only need to do this once ;)

Example to run (if in your home dir).

sudo ~/reboot_required_check.sh

Hope this helps!