======OS - Linux - Debian - Package Management======

=====Notes=====

====Get a list of installed packages====

<code>
dpkg --get-selections
</code>
Source: [[http://www.howtogeek.com/howto/linux/show-the-list-of-installed-packages-on-ubuntu-or-debian/|How-To Geek - Show the List of Installed Packages on Ubuntu or Debian]] \\


====Set apt-get to use 1 specific mirror====

// Tested on stretch. //

To change the apt-get sources.list to only use the ftp.nluug.nl mirror:
<code>
#deb http://ftp.nl.debian.org/debian stretch main contrib
deb https://ftp.nluug.nl/debian stretch main contrib

# security updates
#deb http://security.debian.org stretch/updates main contrib
deb https://ftp.nluug.nl/debian stretch-updates main contrib
</code>


====Clean the apt cache====

Cleans out the apt cache in /var/cache/apt/archives/.
<code>
apt-get clean
</code>
Source:[[https://askubuntu.com/questions/285691/is-it-possible-to-clean-the-apt-cache-from-the-command-line|Ask Ubuntu - Is it possible to clean the APT cache from the command line?]]


=====Delete packages from previous releases=====

For deleting packages that were leftover from previous releases. In this example from debian 7 and 8 on a debian 9 system.

Test removal: 
<code>
apt-get remove --dry-run `dpkg -l | egrep "deb8|deb7" | awk  '{print $2 " "}' | tr -d "\n"`
</code>

Actually remove:
<code>
apt-get remove `dpkg -l | egrep "deb8|deb7" | awk  '{print $2 " "}' | tr -d "\n"`
</code>


=====Force IPv4 usage======

For when apt for some reason thinks it can start using IPv6 in an environment with only IPv4 connectivity.

<code>
echo "Acquire::ForceIPv4 \"True\";" > /etc/apt/apt.conf.d/ForceIPv4
</code>