purge-old-kernels

purge-old-kernels

#!/bin/sh

# removes old kernel packages which stays after kernel upgrades
# on Debian-based systems

# requires: POSIX shell, awk, sed (with -r), grep sort, head, uname
#   printf, echo
#   dpkg, apt-get
#   sudo (? remove?)

# Václav Brožík, 2015, public domain

# TODO
# Notify when the running kernel is not the latest version.

curmver="$(uname -r | sed -nre 's/^([0-9]+\.[0-9]+\.[0-9]+)-[0-9]+.*$/\1/p')"
cursver="$(uname -r | sed -nre 's/^[0-9]+\.[0-9]+\.[0-9]+-([0-9]+).*$/\1/p')"
echo "Currently running kernel: major $curmver minor $cursver"

kpackages="$(dpkg -l linux-\* |
 awk '$1 ~ /^.[^n]/ && $2 ~ /^linux-((signed-)?image(-extra)?|headers)-[0-9]+\.[0-9]+/ {print $2}')"
# kernel packages to consider

mversions="$(printf '%s\n' "$kpackages" |
 sed -re 's/^linux-([a-z]+-)*([0-9]+\.[0-9]+\.[0-9]+)-[0-9]+.*$/\2/' |
 sort -Vu)"
#  awk '{print gensub(/^linux-([a-z]+-)*([0-9]+\.[0-9]+\.[0-9]+)-[0-9]+.*$/, "\\2", "")}' |
# main versions like 3.13.0, 3.16.0 etc.

if ! printf '%s\n' "$mversions" | grep -q "^$curmver" ; then
    echo "Running kernel main version $curmver not found in installed packages."
    exit 1
fi
# echo "$kpackages" | grep -E "^([a-z]+-)+$curmver-$cursver"
if ! printf '%s\n' "$kpackages" | grep -Eq "^([a-z]+-)+$curmver-$cursver" ; then
    echo Running kernel minor version $curmver-$cursver not found in installed packages.
    exit 1
fi

#unset kerfound
todel=""    # about to build list of kernel versions to delete
for ver in $mversions ; do
    echo === $ver ===
    sversions="$(printf '%s\n' "$kpackages" |
     sed -nre 's/^([a-z]+-)+'"$ver"'-([0-9]+).*$/\2/p' |
     sort -u)"
    if test "$ver" = "$curmver" ; then
        # currently running version
        printf '%s\n' "$sversions" |
          sed -re 's/^'"$cursver"'$/&  <--- currenttly running/'
        if ! printf '%s\n' "$sversions" | grep -Eq '^'"$cursver"'$' ; then
            echo Currently running kernel not found.
            exit 1
        fi
        for sver in $(printf '%s\n' "$sversions" |
                        head -n -1 |
                        grep -Ev '^'"$cursver"'$') ; do
            todel="$todel$(test -z "$todel" || echo " ")$ver-$sver"
        done
    else
        # currently not-running versions
        printf '%s\n' "$sversions"
        for sver in $(echo "$sversions" | head -n -1) ; do
            todel="$todel$(test -z "$todel" || echo " ")$ver-$sver"
        done
    fi
done

echo

if test -z "$todel" ; then
    echo Nothing to purge.
    exit
fi

for ver in $todel ; do
    echo "=== purging $ver ==="
    sudo apt-get purge $(printf '%s\n' "$kpackages" | grep -E "^([a-z]+-)+$ver")
done