====== Ubuntu - Packages - Cleanup ======

APT keeps a copy of each downloaded **.deb** file in the directory **/var/cache/apt/archives/**.

In case of frequent updates, this directory can quickly take a lot of disk space with several versions of each package; you should regularly sort through them.

Two commands can be used: **apt-get clean** entirely empties the directory; **apt-get autoclean** only removes packages which can no longer be downloaded (because they have disappeared from the Debian mirror) and are therefore clearly useless (the configuration parameter APT::Clean-Installed can prevent the removal of .deb files that are currently installed).

To save up some space via **apt-get** you can use these commands:

<code bash>
apt-get autoclean
apt-get clean 
</code>

**autoclean** removes unused dependencies, packages which were installed by other packages but which are no longer needed by your system.

**clean** just removes all the packages in the apt cache.  You can also use **autoclean** but clean frees up more space.

----

===== Purge unused packages =====

<code bash>
aptitude clean --purge-unused
</code>

<WRAP important>
**WARNING**:  THIS OPTION CAN CAUSE DATA LOSS. DO NOT USE IT UNLESS YOU KNOW WHAT YOU ARE DOING.
</WRAP>


----

===== Find Package Dependencies =====

When cleaning up a system, it is recommended to consider package dependencies.

To show all the packages which are installed on your system because some package recommends it, but they are not actually dependencies of packages:

<code bash>
aptitude search '?and( ?automatic(?reverse-recommends(?installed)), ?not(?automatic(?reverse-depends(?installed))) )' 
</code>

can give something like this:

<code bash>
i A apt-xapian-index    -   maintenance and search tools for a Xapian index of Debian packages 
i A exim4               -   metapackage to ease Exim MTA (v4) installation 
i A file                -   Determines file type using "magic" numbers 
i A heirloom-mailx      -   feature-rich BSD mail(1)  
</code>

Check the output and if needed remove them all.  

<WRAP important>
**WARNING**: Ensure that package like libc6, sysv-rc, apt or coreutils are not removed.
</WRAP>


<code bash>
aptitude search '?and( ?automatic(?reverse-recommends(?installed)), ?not(?automatic(?reverse-depends(?installed))) )' | awk '{ print $3 }' | xargs dpkg -P
</code>

Then we have the all time favorites to see sizes:

<code bash>
df -h
du -h | grep ^[0-9.]*M | sort -rn
du -h | grep ^[0-9.]*G | sort -rn
</code>