1. Michał Górny
  2. eclean-kernel


eclean-kernel / README



*eclean-kernel* is a small tool aimed at removing old and stale kernel files. It
does not only remove old kernels itself but also tries to remove all related
files including auxiliary files in /boot, kernel modules and even the source


The typical use is::

	eclean-kernel -n 3 -p

where ``-n 3`` is used to keep three newest kernels around, and ``-p`` makes
eclean-kernel only print kernels which would be removed.

In case the results are satisfactory, use::

	eclean-kernel -n 3

to actually remove the kernels.

If you are unsure whether kernel files are mapped correctly, you can use
list mode::

	eclean-kernel -l

which just lists found kernels with file mappings.

Configuration file

Some default options can be specified in ``eclean-kernel.rc`` file in a location
mandated by the XDG configuration directory setting, e.g. ``~/.config/``.

The file format is very simple -- additional command-line options are specified
in shell style. For example, to keep three newest kernels and always preserve
kernel configs, ``~/.config/eclean-kernel.rc`` would contain::

	-n 3 -x config

The options read from config files will be parsed before actual command-line
options, so the latter will override them.

Fiding and mapping kernels

The first task performed by eclean-kernel is finding all currently installed
kernels and matching auxiliary files to them. In order to do that, eclean-kernel
first looks for files named in the form of::


where *PREFIX* is one of the predefined file prefixes representing the file
type, and *VERSION* is a free-form string following it (preferably the kernel

Right now, eclean-kernel supports the following prefixes:

- ``vmlinuz``, ``vmlinux``, ``kernel`` and ``bzImage`` for kernel files,
- ``System.map`` for system.map file,
- ``config`` for kernel configuration.

In case support for additional prefixes is needed, feel free to report a bug.

Files belonging to the same kernel are grouped using the *VERSION* part, e.g. it
is assumed that ``System.map-X.Y.Z`` corresponds to ``vmlinuz-X.Y.Z``.

In addition to that, eclean-kernel looks for kernel modules in::


where *REALVERSION* corresponds to the actual kernel version string used
by the kernel itself. It is read from kernel image itself and it is assumed to
be equal to *VERSION* for libdirs unmatched to any kernel image.

In other words, genkernel-generated ``kernel-genkernel-ARCH-X.Y.Z`` will be
matched to ``System.map-genkernel-ARCH-X.Y.Z`` but also
to ``/lib/modules/X.Y.Z``.

Choosing kernels to remove

The kernel choice algorithm is quite simple:

1. If the kernel is currently used, don't remove it;
2. If the kernel is referenced by a bootloader, don't remove it
   (unless ``--destructive``);
3. If auxiliary files do not map to existing kernel, remove them;
4. If ``--all`` is used, remove the kernel;
5. If kernel is not within *N* newest kernels (where *N* is the argument
   to ``-n``), remove it.

The program always derefences symlinks and counts real path references. Thus,
a particular file will be removed only if all kernels referencing it are removed
as well. This is especially important for shared kernel sources.

Bootloader support

In order to determine kernels currently used, eclean-kernel is supposed to read
configuration files used by the bootloader. Right now, the following bootloaders
are supported (and looked up in the following order):

1. lilo,
2. grub2,
3. grub,
4. yaboot.

There is also a pseudo-bootloader module called *symlinks* which assumes files
symlinked to ``/boot/PREFIX`` and ``/boot/PREFIX.old`` are used.

By default, eclean-kernel uses the first bootloader from the above list for
which a configuration file exists, and uses *symlinks* as a fallback. This can
be changed using ``--bootloader`` argument.

Reporting bugs

Please report bugs either to `the issue tracker`_ or `Gentoo Bugzilla`_. When
reporting a bug, please attach the outputs of::

	eclean-kernel -l
	ls -l /boot /lib/modules/*

If relevant, please attach bootloader configuration files as well.

.. _the issue tracker: https://bitbucket.org/mgorny/eclean-kernel/issues/
.. _Gentoo Bugzilla: https://bugs.gentoo.org/

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