Deleting a package

Similarly it should come as no surprise that the following will deinstall a package, however it will not remove the dependencies:

apt-get purge pidgin

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  pidgin*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 2,270 kB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 92990 files and directories currently installed.)
Removing pidgin ...
Purging configuration files for pidgin ...
Processing triggers for man-db ...
Processing triggers for gconf2 ...
Processing triggers for menu ...

In this last case the configuration files of the package 'pidgin' (basically how its setup) were not deleted from the system. You could use them when installing the same package again and it would work with these settings

If you want the config files deleted also, issue this command:

apt-get --purge remove pidgin

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages will be REMOVED:
  pidgin*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 2,270 kB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 92990 files and directories currently installed.)
Removing pidgin ...
Purging configuration files for pidgin ...
Processing triggers for man-db ...
Processing triggers for gconf2 ...
Processing triggers for menu ...

Note the * after the package name in the output of apt . The asterisk in the output of apt indicates that the configuration files will also be removed.

Hold and/or Downgrade a package

Sometimes it may be necessary to rollback to a previous version of a package or put it on hold, due to a major bug with the latest version you have just installed.

Hold

echo package hold|dpkg --set-selections

To take a package off Hold

echo package install|dpkg --set-selections

To list packages on hold:

dpkg --get-selections | grep hold

Downgrading

Debian does not support downgrading packages. While it may work in simple cases, it could fail spectacularly for other packages. Please refer to Emergency downgrading.

Despite the fact that it is not supportable, downgrading has been known to work for simple packages. The steps for downgrading a simple package using kmahjongg as an example are:

1. comment unstable sources in /etc/apt/sources.list.d/debian.list with a #
2. Add testing sources in /etc/apt/sources.list.d/debian.list , for example:
   

   deb http://ftp.nl.debian.org/debian/ testing main contrib non-free
   

3. apt-get update
   

4. apt-get install kmahjongg/testing
   

5. Put the newly installed package on hold with:
   

   echo kmahjongg hold|dpkg --set-selections
   

6. comment <#>the testing sources in /etc/apt/sources.list.d/debian.list with and uncomment the unstable sources so that you get back to using unstable sources, then:

7. apt-get update
   

When you do want to get the latest version of the package just do this:

echo kmahjongg install|dpkg --set-selections
apt-get update
apt-get install kmahjongg

apt-mark

apt-mark is a useful tool that shows you which packages are automatically or manually installed and offers the system administrator the opportunity to mark and hold packages that are not to be removed automatically. Read:

man apt-mark

Upgrade of an Installed System - dist-upgrade - Overview

If the whole system is to be upgraded this is achieved through a dist-upgrade. You should always check Current Warnings on the aptosid main web site, and check the warnings against the packages that your system wants to dist-upgrade. If you need to hold a package refer to Downgrade and Hold a package

An 'upgrade' only of 'debian sid' is not recommended.

Frequency of a dist-upgrade

dist-upgrade as routinely as you can, ideally once every week or two, at least 1 time per month to be safe. A dist-upgrade initiated only every 2 to 3 months should be considered the safe outer limit. For non-standard packages, or self compiled packages, you need to be much more careful with upgrading, since those may break your system at any time due to incompatibilities.

After the database is updated with apt-get update, one can find out which packages have new/newer versions: (first install apt-show-versions)

apt-show-versions -u
libpam-runtime/unstable upgradeable from 0.79-1 to 0.79-3
passwd/unstable upgradeable from 1:4.0.12-5 to 1:4.0.12-6
teclasat/unstable upgradeable from 0.7m02-1 to 0.7n01-1
libpam-modules/unstable upgradeable from 0.79-1 to 0.79-3.........

The update of a single package including its dependencies can for example (for gcc-4.0) be done with:

apt-get install gcc-4.0
Reading package lists... Done
Building dependency tree... Done
gcc-4.0 is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and xxx not upgraded

Just downloading

A little known and great option to do a check for what packages are in a dist-upgrade is the -d flag:

apt-get update && apt-get dist-upgrade -d

The -d allows you to download the dist-upgrade without installing it whilst in X from the konsole and allows you to do the dist-upgrade in init 3 at a later time. This also gives you the chance to check warnings against the list as it wisely gives you the option to proceed or abort like this:

apt-get dist-upgrade -d
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following NEW packages will be installed:
  elinks-data
The following packages have been kept back:
  git-core git-gui git-svn gitk icedove libmpich1.0ldbl
The following packages will be upgraded:
  alsa-base bsdutils ceni configure-ndiswrapper debhelper
  discover1-data elinks file fuse-utils gnucash.........
35 upgraded, 1 newly installed, 0 to remove and 6 not upgraded.
Need to get 23.4MB of archives.
After this operation, 594kB of additional disk space will be used.
Do you want to continue [Y/n]?Y 

Y will download the upgraded packages without touching the installed system.

After the 'dist-upgrade -d' has downloaded, and wish to complete the dist-upgrade, immediately or at a later time, please follow these steps:

dist-upgrade - The Steps

## Log out of KDE.  
## Go to Textmode by doing Ctrl+Alt+F1
## logon as root, and then type:
service kdm stop  ##If using another window manager replace kdm, for example with gdm
apt-get update
apt-get dist-upgrade
apt-get clean
service kdm start ##If using another window manager replace kdm, for example with gdm

If you do not go to init 3, well tough for you, you have been warned!

The Reasons NOT to use anything else but apt-get for a dist-upgrade

Package managers like adept, aptitude, synaptic and kpackage are not always able to account for the huge amount of changes which happen in Sid (depedency changes, name changes, maintainer script changes, ...).

This is not the fault of the developers of those tools though, they write a excellent tools and fabulous for the debian stable branch, they are simply just not suitable for the very special needs of Debian Sid.

Use whatever you like to search for packages, but stick with apt-get for actually installing/removing/dist-upgrading.

Package managers like adept, aptitude, synaptic and kpackage are at the least, non-deterministic (for complex package selection), mix that with a quickly moving target like sid and even worse an external repository of questionable quality (we don't use or recommend those, but they're a reality on your user systems) and you will be courting disaster.

The other item to note is that all of these types of GUI package managers need to run in in X, and in doing a dist-upgrade in X, (or even an 'upgrade' which is not recommended), you will end up damaging up your system beyond repair, maybe not today or tomorrow, however in time you will.

apt-get on the other hand strictly does what it is asked to do, if there is any breakage you can pinpoint and debug/ fix the cause, if apt-get wants to remove half of the system (due to library transitions) it's the admin's call (that means you) to have at least a serious look.

This is the reason why debian builds use apt-get, not the other package manager tools.

Searching for a package with apt-cache

Another very useful command in the APT-system is apt-cache; it searches the APT-Database and shows information on packages; e.g. a list of all packages, that contain or address "aptosid" and "manual" is obtained by:

$ apt-cache search aptosid manual
.......
aptosid-manual-common - the official aptosid manual - common files
aptosid-manual-es - the official Spanish aptosid manual
aptosid-manual-de - the official German aptosid manual
aptosid-manual-el - the official Greek aptosid manual
aptosid-manual - the official aptosid manual - all languages
aptosid-manual-pt-br - the official Brazilian Portuguese aptosid manual
aptosid-manual-en - the official English aptosid manual
aptosid-manual-reader - aptosid manual reader

If you want more information on a particular package, you can use:

$ apt-cache show aptosid-manual-en
Package: aptosid-manual-en
Priority: optional
Section: doc
Installed-Size: 1088
Maintainer: Kel Modderman <kel@otaku42.de>
Architecture: all
Source: aptosid-manual
Version: 01.12.2007.06.03-1
Depends: aptosid-manual-common
Filename: pool/main/s/aptosid-manual/aptosid-manual-en_00.00.2010.08.14-1_all.deb
Size: 391222
MD5sum: 60f2175c3c5709745a4b4256ccc3c49d
SHA1: e275a0b27628b6aa210a4ced48d3646b438e78b8
SHA256: 2792580c7a091521301064180a1d0d8901f0a4af407b90432b9f8d8b6b3603ca
Description: the official en aptosid manual
 This manual is divided into common sections, for example, .......

All installable versions of the package (they depend on your sources.list) can be listed by typing:

$ apt-cache policy aptosid-manual-xx
aptosid-manual-xx:
  Installed: (none)
  Candidate: (none)
  Version table:
        500 http://aptosid.com sid/main Packages

A complete description of the APT-System can be found at APT-HOWTO