How to easily remove old kernels in Ubuntu 20.04 LTS?

Question

I have old Linux kernel versions that I don't use so I was trying to remove them.

List of installed kernels from dpkg --list | grep linux-image

linux-image-5.4.0-26-generic (5.4.0-26.30)   
linux-image-5.4.0-33-generic (5.4.0-33.37)
linux-image-5.4.0-37-generic (5.4.0-37.41)

Answer 1

Here are the steps to remove unused kernels.

Check what current kernel You run:

uname -a
Linux blackhole 5.6.13-050613-lowlatency #202005141310 SMP PREEMPT Thu May 14 13:17:41 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

I am running 5.6.13-050613-lowlatency

List all installed kernels in Your OS:

dpkg --list | egrep -i --color 'linux-image|linux-headers|linux-modules' | awk '{ print $2 }'
linux-headers-5.6.11-050611
linux-headers-5.6.11-050611-lowlatency
linux-headers-5.6.13-050613
linux-headers-5.6.13-050613-lowlatency
linux-image-unsigned-5.6.11-050611-lowlatency
linux-image-unsigned-5.6.13-050613-lowlatency
linux-modules-5.6.11-050611-lowlatency
linux-modules-5.6.13-050613-lowlatency

Uninstall kernels You don't need:

sudo apt purge linux-headers-5.6.11-050611  linux-headers-5.6.11-050611-lowlatency linux-image-unsigned-5.6.11-050611-lowlatency linux-modules-5.6.11-050611-lowlatency

Answer 2

You can try out this script

remove_old_kernels.sh

#!/bin/bash
# Run this script without any param for a dry run
# Run the script with root and with exec param for removing old kernels after checking
# the list printed in the dry run
uname -a
IN_USE=$(uname -a | awk '{ print $3 }')
echo "Your in use kernel is $IN_USE"
OLD_KERNELS=$(
    dpkg --list |
        grep -v "$IN_USE" |
        grep -Ei 'linux-image|linux-headers|linux-modules' |
        awk '{ print $2 }'
)
echo "Old Kernels to be removed:"
echo "$OLD_KERNELS"
if [ "$1" == "exec" ]; then
    for PACKAGE in $OLD_KERNELS; do
        yes | apt purge "$PACKAGE"
    done
else
    echo "If all looks good, run it again like this: sudo remove_old_kernels.sh exec"
fi

Run it like this for a dry run:

remove_old_kernels.sh

If all looks good, run it again like this:

sudo remove_old_kernels.sh exec

Answer 3

Just taking Michal's answer a little further. I didn't want to type the kernels to delete everytime so I decided to use files instead.

Write all the current kernels you have on a file.

dpkg --list | egrep -i --color 'linux-image|linux-headers|linux-modules' | awk '{ print $2 }' > kernels.txt

Filter your currently used kernel out of the file using grep.

grep -v $(uname -r) kernels.txt > kernels_to_delete.txt

Verify your current kernel is not present in the delete list. Don't skip this. Ensures you don't mistakenly delete all the kernels.

grep $(uname -r) kernels_to_delete.txt

Delete all the unused kernels in one go.

cat kernels_to_delete.txt | xargs sudo apt purge -y

Answer 4

An update to @alex Burdusel's script would be the following:

#!/bin/bash -e
# Run this script without any arguments for a dry run
# Run the script with root and with exec arguments for removing old kernels and modules after checking
# the list printed in the dry run
uname -a
IN_USE=$(uname -a | awk '{ print $3 }')
echo "Your in use kernel is $IN_USE"
OLD_KERNELS=$(
    dpkg --get-selections |
        grep -v "linux-headers-generic" |
        grep -v "linux-image-generic" |
        grep -v "linux-image-generic" |
        grep -v "${IN_USE%%-generic}" |
        grep -Ei 'linux-image|linux-headers|linux-modules' |
        awk '{ print $1 }'
)
echo "Old Kernels to be removed:"
echo "$OLD_KERNELS"
OLD_MODULES=$(
    ls /lib/modules |
    grep -v "${IN_USE%%-generic}" |
    grep -v "${IN_USE}"
)
echo "Old Modules to be removed:"
echo "$OLD_MODULES"
if [ "$1" == "exec" ]; then
  apt-get purge $OLD_KERNELS
  for module in $OLD_MODULES ; do
    rm -rf /lib/modules/$module/
  done
fi

This solves the issue that it tries to delete the following packages:

linux-headers-generic
linux-image-generic
linux-headers-5.17.5-76051705 # if 5.17.5-76051705-generic is the current kernel

This script was modified to purge all packages at once, and also delete any remaining module directories in /lib/modules/

Answer 5

Just use this:

sudo apt-get autoremove --purge

Answer 6

To easily remove older versions kernels, e.g. kernels starting from 4.0 and so on.

sudo apt-get purge linux-image-4.*

Answer 7

autoremove will only remove packages that are automatically installed. If you ever updated or added a kernel package manually autoremove will not remove it. If you ever "held" a kernel version autoremove will not remove it. If you're wondering why Ubuntu is filling up your boot partition with kernels you no longer use it's likely one of these two reasons.

# Unhold all packages
dpkg --get-selections | grep hold | awk '{ print $1, "install" }' | dpkg --set-selections
Mark all "manually installed" kernel packages as "automatically installed"
for f in $(apt-mark showmanual | grep linux-); do
    apt-mark auto $f
done
Remove all packages that are no longer needed
apt-get -y autoremove --purge

Answer 8

I derived this script from previous answers. It should reserve the current kernel and one previous kernel. As stated in previous answers, execute once without any arguments for a dry run. Then run as root with 1 argument as 'exec' to actually remove the old kernels.

#!/bin/bash -e
IN_USE=$(uname -a | awk '{ print $3 }')
echo "Your in use kernel is $IN_USE"
CUR_KERNELS=$(dpkg --get-selections | grep linux-image | grep install | awk '{print $1}')
echo
echo "Current Kernels are:"
echo "$CUR_KERNELS"
OLD_KERNELS=$(dpkg --get-selections | grep linux | grep deinstall | awk '{print $1}')
echo
echo "Old Kernels to be removed:"
echo "$OLD_KERNELS"
if [ "$1" == "exec" ]; then
  apt-get purge $OLD_KERNELS
fi

Answer 9

As for easy solution, use a utility called linux-purge that is made just for the purpose, and that is supposed to work by any release of Ubuntu later than 12.04. The utility is implemented using Bash.

Here is my answer with more details to another similar question.

Answer 10

Further improvement to the script:

Courtesy of @eitch

This version filters out the newer kernels. In earlier versions, the newer kernels will also get purged.

This script defaults to "dry-run" but if the $1 is anything other than "dry-run" or "exec" then the usage help text is displayed.

#!/bin/bash -e
Function to print usage instructions
print_usage() {
  echo "Usage: $0 [dry-run|exec]"
  echo "  dry-run: List old kernels and modules without removing them (default)"
  echo "  exec: Remove the listed old kernels and modules (requires root privileges)"
}
Function to compare kernel version numbers
Returns 1 if version1 is greater than version2, 0 if equal, and -1 if lesser
compare_versions() {
  local version1=(${1//./ })
  local version2=(${2//./ })
for i in {0..2}; do
    if [[ ${version1[i]} -gt ${version2[i]} ]]; then
      return 1
    elif [[ ${version1[i]} -lt ${version2[i]} ]]; then
      return -1
    fi
  done
return 0
}
Check for valid input arguments
if [[ $# -gt 1 ]] || { [[ $# -eq 1 ]] && [[ "$1" != "dry-run" ]] && [[ "$1" != "exec" ]]; }; then
  print_usage
  exit 1
fi
Display current running kernel
uname -a
IN_USE=$(uname -a | awk '{ print $3 }')
echo "Your in-use kernel is $IN_USE"
Find old kernels
OLD_KERNELS=$(
  dpkg --get-selections |
  grep -v "linux-headers-generic" |
  grep -v "linux-image-generic" |
  grep -Ei 'linux-image|linux-headers|linux-modules' |
  awk '{ print $1 }' |
  grep -v "${IN_USE}"
)
Filter out newer kernels
FILTERED_KERNELS=""
for kernel in $OLD_KERNELS; do
  kernel_version=$(echo "$kernel" | grep -oP '(?<=linux-image-|linux-headers-|linux-modules-)[0-9]+(.[0-9]+){0,2}' || true)
  if [[ ! -z "$kernel_version" ]]; then
    compare_versions "$kernel_version" "$IN_USE"
    if [[ $? -eq -1 ]]; then
      FILTERED_KERNELS+="$kernel"$'\n'
    fi
  else
    FILTERED_KERNELS+="$kernel"$'\n'
  fi
done
OLD_KERNELS="$FILTERED_KERNELS"
Find old modules
OLD_MODULES=$(
  ls /lib/modules |
  grep -v "${IN_USE}" |
  while read -r module; do
    module_version=$(echo "$module" | grep -oP '[0-9]+(.[0-9]+){0,2}' || true)
    if [[ ! -z "$module_version" ]]; then
      compare_versions "$module_version" "$IN_USE"
      if [[ $? -eq -1 ]]; then
        echo "$module"
      fi
    else
      echo "$module"
    fi
  done
)
Display old kernels and modules
echo "Old Kernels to be removed:"
echo "$OLD_KERNELS"
echo "Old Modules to be removed:"
echo "$OLD_MODULES"
Remove old kernels and modules if "exec" argument is passed
if [ "$1" == "exec" ]; then
Check for root privileges
if [ "$(id -u)" != "0" ]; then
    echo "Error:This operation requires root privileges. Please run the script as root or use 'sudo'."
    exit 1
  fi
Remove Old Kernel
apt-get purge $OLD_KERNELS
Remove Old Modules
for module in $OLD_MODULES ; do
    rm -rf /lib/modules/$module/
  done
fi

Answer 11

Not one of these worked for me.

Had to use:

sudo dpkg --purge linux.modules-extra-5.4.0-84.94