Tool to remove unused kernels that were installed automatically in Debian/Ubuntu.
This tool removes those kernel packages marked as candidate for autoremoval. Those packages are generally installed via Unattended upgrade or meta-packages.
By default, on apt 1.0 and below, the booted kernel, the latest-installed kernel and the latest kernel are set to "NeverAutoRemove". Or, for apt 1.2 and above, the booted kernel, the latest-installed kernel, the latest kernel and the second-latest kernel are set to "NeverAutoRemove".
- Ubuntu has multiple suggestions on how to remove kernels:
- https://help.ubuntu.com/community/RemoveOldKernels
A great recommendation is to make use of unattended-upgrades u-u (debian, ubuntu). Since version 1.0 (debian, ubuntu) u-u removes unused kernel packages by default (Remove-Unused-Kernel-Packages). Some distribution versions may not make reference or may comment out that setting in its configuration, but unless it is explicitly disabled, u-u will attempt to remove unused kernels. More info here.
For scenarios where u-u is not available or older than 1.0, kthresher is still a good option.
thresher - A device that first separates the head of a stalk of grain from the straw, and then further separates the kernel from the rest of the head.
Table of Contents
Whenever a package is auto-installed and there is no other dependency for it, the package is marked as a candidate for autoremoval, there is an exception if the APT configuration does have the package marked as "NeverAutoRemove".
When a kernel image is installed the postinstall script will issue the run-parts on /etc/kernel/postinst.d/ and /etc/kernel/postinst.d/${version} if any exist. The run-parts script will run each one of the scripts located in that directory, e.g.
# ls -1 /etc/kernel/postinst.d/
apt-auto-removal
initramfs-tools
update-notifier
x-grub-legacy-ec2
zz-update-grubAll the scripts found by run-parts are executed on post install of the kernel package and the output of apt-get install/upgrade/dist-upgrade will show them, e.g.
run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 3.13.0-96-generic /boot/vmlinuz-3.13.0-96-generic
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 3.13.0-96-generic /boot/vmlinuz-3.13.0-96-generic
run-parts: executing /etc/kernel/postinst.d/update-notifier 3.13.0-96-generic /boot/vmlinuz-3.13.0-96-generic
run-parts: executing /etc/kernel/postinst.d/x-grub-legacy-ec2 3.13.0-96-generic /boot/vmlinuz-3.13.0-96-generic
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 3.13.0-96-generic /boot/vmlinuz-3.13.0-96-genericThe first script "apt-auto-removal" takes care of adding a configuration in /etc/apt/apt.conf.d/01autoremove-kernels this script generates that list based on the logic described above, it means that the NeverAutoRemove may have anything between two to three kernels listed.
wget -O kthresher https://raw.githubusercontent.com/rackerlabs/kthresher/master/kthresher.py
chmod u+x kthresherpip install kthresheror
pip install git+https://github.com/rackerlabs/kthresher.gitgit clone https://github.com/rackerlabs/kthresher.git
cd kthresher && python setup.py install$ kthresher -h
usage: kthresher [-h] [-c FILE] [-d] [-H] [-k [N]] [-p] [-s] [-v] [-V]
Purge Unused Kernels.
optional arguments:
-h, --help show this help message and exit
-c FILE, --config FILE
Config file, default is /etc/kthresher.conf
-d, --dry-run List unused kernel images available to purge(dry run).
Is always verbose.
-H, --headers Include the search for kernel headers.
-k [N], --keep [N] Number of kernels to keep, default 1.
-p, --purge Purge Unused Kernels.
-s, --show-autoremoval
Show kernel packages available for autoremoval.
-v, --verbose Be verbose.
-V, --version Print version.
# kthresher -d
INFO: Attempting to read /etc/kthresher.conf.
INFO: Config file /etc/kthresher.conf is empty or does not exist, ignoring.
INFO: Options: {'purge': False, 'verbose': False, 'dry_run': True, 'keep': 1}
INFO: ----- DRY RUN -----
INFO: Running kernel is linux-image-3.13.0-83-generic v[3.13.0-83.127]
INFO: Attempting to keep 1 kernel package(s)
INFO: Found 4 kernel image(s) installed and available for autoremoval
INFO: Pre-sorting: ['3.16.0-60.80~14.04.1', '3.13.0-77.121', '3.13.0-63.103', '3.16.0-33.44~14.04.1']
INFO: Post-sorting: ['3.13.0-63.103', '3.13.0-77.121', '3.16.0-33.44~14.04.1', '3.16.0-60.80~14.04.1']
INFO: Purging packages from version: 3.13.0-63.103
INFO: Purging: linux-image-extra-3.13.0-63-generic
INFO: Purging: linux-image-3.13.0-63-generic
INFO: Purging packages from version: 3.13.0-77.121
INFO: Purging: linux-image-3.13.0-77-generic
INFO: Purging: linux-image-extra-3.13.0-77-generic
INFO: Purging packages from version: 3.16.0-33.44~14.04.1
INFO: Purging: linux-image-3.16.0-33-generic
# kthresher -s
List of kernel packages available for autoremoval:
Version Package
3.13.0.83.89 linux-generic
3.13.0-51.84 linux-headers-3.13.0-51
3.13.0-51.84 linux-headers-3.13.0-51-generic
3.13.0-71.114 linux-headers-3.13.0-71
3.13.0-71.114 linux-headers-3.13.0-71-generic
3.13.0-77.121 linux-headers-3.13.0-77
3.13.0-77.121 linux-headers-3.13.0-77-generic
3.13.0-79.123 linux-headers-3.13.0-79
3.13.0-79.123 linux-headers-3.13.0-79-generic
3.13.0-63.103 linux-image-3.13.0-63-generic
3.13.0-77.121 linux-image-3.13.0-77-generic
3.16.0-33.44~14.04.1 linux-image-3.16.0-33-generic
3.16.0-60.80~14.04.1 linux-image-3.16.0-60-generic
3.13.0-63.103 linux-image-extra-3.13.0-63-generic
3.13.0-77.121 linux-image-extra-3.13.0-77-generic
3.13.0.83.89 linux-image-generic
# kthresher -p -k3 -v
INFO: Attempting to read /etc/kthresher.conf.
INFO: Config file /etc/kthresher.conf is empty or does not exist, ignoring.
INFO: Options: {'purge': True, 'verbose': True, 'dry_run': False, 'keep': 3}
INFO: Running kernel is linux-image-3.13.0-83-generic v[3.13.0-83.127]
INFO: Attempting to keep 3 kernel package(s)
INFO: Found 4 kernel image(s) installed and available for autoremoval
INFO: Pre-sorting: ['3.16.0-60.80~14.04.1', '3.13.0-77.121', '3.13.0-63.103', '3.16.0-33.44~14.04.1']
INFO: Post-sorting: ['3.13.0-63.103', '3.13.0-77.121', '3.16.0-33.44~14.04.1', '3.16.0-60.80~14.04.1']
INFO: Purging packages from version: 3.13.0-63.103
INFO: Purging: linux-image-extra-3.13.0-63-generic
INFO: Purging: linux-image-3.13.0-63-generic
Fetched 0 B in 0s (0 B/s)
(Reading database ... 169514 files and directories currently installed.)
Removing linux-image-extra-3.13.0-63-generic (3.13.0-63.103) ...
run-parts: executing /etc/kernel/postinst.d/apt-auto-removal 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
update-initramfs: Generating /boot/initrd.img-3.13.0-63-generic
run-parts: executing /etc/kernel/postinst.d/zz-update-grub 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.16.0-60-generic
Found initrd image: /boot/initrd.img-3.16.0-60-generic
Found linux image: /boot/vmlinuz-3.16.0-33-generic
Found initrd image: /boot/initrd.img-3.16.0-33-generic
Found linux image: /boot/vmlinuz-3.13.0-83-generic
Found initrd image: /boot/initrd.img-3.13.0-83-generic
Found linux image: /boot/vmlinuz-3.13.0-77-generic
Found initrd image: /boot/initrd.img-3.13.0-77-generic
Found linux image: /boot/vmlinuz-3.13.0-63-generic
Found initrd image: /boot/initrd.img-3.13.0-63-generic
done
Purging configuration files for linux-image-extra-3.13.0-63-generic (3.13.0-63.103) ...
Removing linux-image-3.13.0-63-generic (3.13.0-63.103) ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
update-initramfs: Deleting /boot/initrd.img-3.13.0-63-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.16.0-60-generic
Found initrd image: /boot/initrd.img-3.16.0-60-generic
Found linux image: /boot/vmlinuz-3.16.0-33-generic
Found initrd image: /boot/initrd.img-3.16.0-33-generic
Found linux image: /boot/vmlinuz-3.13.0-83-generic
Found initrd image: /boot/initrd.img-3.13.0-83-generic
Found linux image: /boot/vmlinuz-3.13.0-77-generic
Found initrd image: /boot/initrd.img-3.13.0-77-generic
done
Purging configuration files for linux-image-3.13.0-63-generic (3.13.0-63.103) ...
Examining /etc/kernel/postrm.d .
run-parts: executing /etc/kernel/postrm.d/initramfs-tools 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
run-parts: executing /etc/kernel/postrm.d/zz-update-grub 3.13.0-63-generic /boot/vmlinuz-3.13.0-63-generic
# kthresher -c myconf.conf
INFO: Attempting to read myconf.conf.
INFO: Options found: ['keep', 'dry_run'].
INFO: Valid setting found "keep"
INFO: keep = 1
INFO: Valid setting found "dry_run"
INFO: dry_run = True
INFO: Options: {'purge': False, 'verbose': True, 'dry_run': True, 'keep': 1}
INFO: ----- DRY RUN -----
INFO: Running kernel is linux-image-3.13.0-83-generic v[3.13.0-83.127]
INFO: Attempting to keep 1 kernel package(s)
INFO: Found 2 kernel image(s) installed and available for autoremoval
INFO: Pre-sorting: ['3.16.0-60.80~14.04.1', '3.16.0-33.44~14.04.1']
INFO: Post-sorting: ['3.16.0-33.44~14.04.1', '3.16.0-60.80~14.04.1']
INFO: Purging packages from version: 3.16.0-33.44~14.04.1
INFO: Purging: linux-image-3.16.0-33-generic
Content of myconf.conf is: .. code-block:
[main] keep = 1 dry_run = yes #purge = yes
# kthresher -v -d -H
INFO: Attempting to read /etc/kthresher.conf.
INFO: Options found: ['keep', 'dry_run', 'purge', 'verbose'].
INFO: Valid setting found "keep"
INFO: keep = 2
INFO: Valid setting found "dry_run"
INFO: dry_run = False
INFO: Valid setting found "purge"
INFO: purge = True
INFO: Valid setting found "verbose"
INFO: verbose = True
INFO: Options: {'verbose': True, 'dry_run': True, 'keep': 2, 'purge': True, 'headers': True}
INFO: ----- DRY RUN -----
INFO: Running kernel is linux-image-3.13.0-83-generic v[3.13.0-83.127]
INFO: Attempting to keep 2 kernel package(s)
INFO: Found 4 kernel image(s) installed and available for autoremoval
INFO: Pre-sorting: ['3.16.0-60.80~14.04.1', '3.16.0-33.44~14.04.1', '3.13.0-85.129', '3.13.0-79.123']
INFO: Post-sorting: ['3.13.0-79.123', '3.13.0-85.129', '3.16.0-33.44~14.04.1', '3.16.0-60.80~14.04.1']
INFO: Purging packages from version: 3.13.0-79.123
INFO: Purging: linux-image-3.13.0-79-generic
INFO: Purging: linux-headers-3.13.0-79-generic
INFO: Purging: linux-headers-3.13.0-79
INFO: Purging packages from version: 3.13.0-85.129
INFO: Purging: linux-image-3.13.0-85-generic
INFO: Purging: linux-headers-3.13.0-85
INFO: Purging: linux-headers-3.13.0-85-generic
The below code can be used to install up to a fixed amount of kernels and headers if available of the form "linux-(image|headers)-[0-9].*-(generic|amd64)" at the end it should end up with two or three kernels in the NeverAutoRemove list, including the latest, the prior to latest and the running kernel.
#!/usr/bin/env python
'''Installs available linux-image-* and linux-headers-*
And set them for autoremoval, so kthresher can be used for testing.
'''
import re
import apt
import sys
from platform import uname
def autorm_install(pkgs):
'''Install a list of packages and set them autoremovable.
'''
latest_kernel = ''
ac = apt.Cache()
for pkg in pkgs:
latest_kernel = pkg
k = ac[pkg]
if not k.is_installed:
k.mark_install(from_user=False)
try:
ac.commit(install_progress=None)
except apt.cache.LockFailedException as lfe:
print('{}, are you root?'.format(lfe))
sys.exit(1)
except SystemError:
print('Something failed')
sys.exit(1)
def get_pkg(regex):
'''Get a list of packages available that match the regex.
'''
pkgs = []
ac = apt.Cache()
ac.update()
for pkg in ac:
if re.match(regex, pkg.name):
# ignore running kernel
if pkg.name == 'linux-image-{0}'.format(uname()[2]):
continue
pkgs.append(pkg.name)
return pkgs
def main():
limit = 5
if len(sys.argv) > 1:
try:
limit = int(sys.argv[1])
except:
print("Use an integer as the limit of pkgs to install.")
sys.exit(1)
print("Installing {} kernels/headers if available...".format(limit))
kernel_regex = "^linux-image-\d\..*-(generic|amd64)$"
header_regex = "^linux-headers-\d\..*-(generic|amd64)$"
kernels = get_pkg(kernel_regex)
headers = get_pkg(header_regex)
pkgs = kernels[0:limit] + headers[0:limit]
print("Installing {} packages total\n\tkernels: {}\n\theaders: {}"
.format(len(pkgs), kernels[0:limit], headers[0:limit]))
autorm_install(pkgs)
if __name__ == "__main__":
main()Submit Bug reports, feature requests via issues.
The art was created by Carlos Garcia <hellyeahdesign AT gmail DOT com> and released under CC BY-SA 4.0
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