Some preliminary notes:
* This is a pre release version! Be careful, and take its results
with a grain of salt.
* cruft does not make any assumptions about the things you may have
in places like /usr/local, /var/tmp, /tmp, or any local mount-
points. cruft uses explanation programs from /etc/cruft/explain
to determine which files are meant to be on the system. To cover
all of /usr/local, create a script like:
in the directory /etc/cruft/explain/ called, eg, usr_local. It
needs to be executable.
* If you have any suggestions on how to improve cruft, or if you
make a /usr/lib/cruft/filters/* file for another package, please
mail me the results for inclusion in a future release.
And some notes on how it works, and what it does:
cruft is a program to look over your system for anything that shouldn't
be there, but is; or for anything that should be there, but isn't.
The basis for most of its comparisons is dpkg's installed database
(found in /var/lib/dpkg/info), but it also knows about such things as
the alternatives database, ext2fs lost+found directories, home
directories, and takes care to avoid complaining about most of the
deliberately variable directories, such as /usr/local and /usr/src.
cruft does its work by first building up lists of all the files that
should be on the system, by querying the various databases on the system.
It puts these files into /var/spool/cruft/expl_foobar. This can be thought
of as a list of all the files whose existence is explained by "foobar".
Having done so, it then produces a list of all the files on all
mounted file systems (except proc), in /var/spool/cruft/file_* (to be
precise: file_root for /, file_in_mount for /mount, and for nested
mountpoints, file_in_mount_point for /mount/point).
A few intricacies also need to be handled throughout the above.
Firstly, we'd like to treat two files as the same if they have the
same name and are in the same directory, but we'd like to consider, eg
/usr/bin/X11/app and /usr/X11R6/bin/app. We thus filter all our
explanations through canonical to get rid of symlinks in the path.
We also need to take care of files that aren't included in packages
themselves, but which are instead generated in pre and postinst's, or
at runtime. We do this by matching files against shell-patterns in the
.extrafiles lists of packages and files in /etc/cruft/filters/*.
Having done all this, we then compare the filenames in expl_* and
file_*, to determine any files that appear in one group but not the
other. These listing are separated into /var/spool/cruft/miss_foobar
(for files that foobar expected, but that didn't appear), and
/var/spool/cruft/unex_in_mount (for files mounted on "mount" that
weren't explained by anything).
Finally, we list the contents of miss_* and unex_* in a moderately
human readable form that we dump onto stdout.
And that's about it.
Anthony Towns <firstname.lastname@example.org>