A collection of useful tools for system administrators
======================================================

License: GPLv3 or higher

This repositry contains a collection of useful tools for the use
in system administration.



fkumount (Forcibly Killing UMOUNT)
----------------------------------

Umount a mount point. This Python [1] script umounts a directory. If the
mount point is busy, it tries to find out which processes are still
accessing it and kills them (if possible). It then tries to umount the same
mount point again and again until that is either successful or a timeout is
reached. (It tries multiple times to kill the processes accessing that mount
point.)

Multiple mount points may be specified. With threading, this utility tries
to unmount those mount points simultaneously. The reationale for this is
that in some circumstances, the mount utility itself may hang on some mount
points (if there is a kernel problem) and this guarantees that every mount
point that can be umounted sanely, will be. (The threading part is why it's
written in Python.)

If certain mount points do not exist, they will be ignored. If no valid
mount points are specified, an error will be returned.

If certain paths are not mountpoints, they will be ignored but no error will
be raised. This means that once this utility completes with exit status 0,
there is definitely nothing mounted at the given paths.

It may seem that fuser -mk $PATH && umount $PATH should achieve the same,
but fuser -m does not find all processes that still access the mount point -
only lsof +f -- $PATH will find all (?) of them. This utility makes use of
lsof and provides convenience functionality around it.

Note that while several retries in acquiring the process list are done (to
catch the case when a process forks at the wrong time), the entire logic is
still prone to race conditions. There is no guarantee that this will always
work properly - especially against malicious programs.

Some may refer to the -l option of umount in recent versions; that is not
what this utility is supposed to do. The idea behind this utility is that
after a successful run the underlying device file can be safely removed
without any data loss (other than what may have occurred by killing the
processes still accessing it). The -l option leaves the device file still in
use, it only frees up the path on additional accesses. Both have their uses,
but this tool does something different.

[1] Should work with any Python version from 2.3 onwards; but so far tested
only with 2.6, 2.7 and 3.2.

detect-debmirror (Detect main Debian mirror)
--------------------------------------------

This utility tries to detect the main mirror used in a Debian or derivative
(such as Ubuntu) installation. The logic behind it is that it looks for the
source of all of the 'essential' packages. Most of them will come from the
main mirror used in the installation, some of them will come from
debian-security or similar. It thus uses the mirror with the most packages
in essential.

The rationale behind this tool is that it is not entirely obvious what the
primary mirror is, especially if multiple repositories are included and
sources.list.d is used. Using 'essential' packages seems to be the most
straight-forward way of detecting that. This may still break down in very
exotic situation but seems to be a sane default in most cases.

Use case: for any kind of script that wants to automatically detect the
locally used Debian mirror (which may be a local one behind a Firewall, for
example) in order to run debootstrap (for containers, virtualisation, build
chroots, ...).

This is not available as a library function, since python-apt and APT in
general keep quite a few things in the global application state (i.e. global
variables and such) so that it is best to just spawn this utility directly,
even from binary applications.

Please note that any automated system should probably fall back to a sane
default if this utility fails.

Only works with Python 2.x. Only works for Squeeze and later. (Tested with
Squeeze and Wheezy.)