== Debian and derivatives ==
Much of why Debian is a strong Linux distribution comes from the core of Debian namely its package management. Everything in Debian
There are over 29 thousand software packages available for Debian
And <abbr title="Advanced Package Tool">Apt</abbr> is simply awesome! Learn more at https://wiki.debian.org/Apt or https://help.ubuntu.com/14.04/serverguide/package-management.html
You can also use the web interface at http://packages.ubuntu.com/
=== Remove old kernels ===
Kernels take up a lot of disk space. And once you've got a new one, the old ones really don't serve a purpose. <code>autoremove</code> is supposed to remove old kernels (keeping the currently running kernel plus the prior one or two for backups).
<source lang="bash">
sudo apt-get autoremove
</source>
But sometimes old kernels are left lying around. Maybe a lot of them. I'm not sure why, because normally you would only be left with 2 or 3 kernels if you run autoremove (perhaps this is because you have old virtualboxes?).
The post-install script <code>/etc/kernel/postinst.d/apt-auto-removal</code> is responsible for keeping track of what to preserve. And it writes a manifest to <code>/etc/apt/apt.conf.d/01autoremove-kernels</code>.
<source lang="bash">
# run the post-install script
sudo /etc/kernel/postinst.d/apt-auto-removal
# see what's reserved
cat /etc/apt/apt.conf.d/01autoremove-kernels
</source>
Let's use <code>dpkg</code> to see all the kernels that are currently installed. Note: there are other related packages like headers (<code>linux-headers-*</code>), but those are dependencies of the kernel images, and will be removed when we remove the images so we don't need to even look at them.
<source lang="bash">
# the last pipe uses a simple extended grep to take the meta package 'linux-image-generic' out of our list
dpkg -l linux-image* | awk '/^ii/ { print $2 }' | grep -e [0-9]
# more complete perl-compatible regex to highlight the kernel release number
dpkg -l linux-image* | awk '/^ii/ { print $2 }' | grep -P '[0-9]+\.[0-9]+\.[0-9\-]+[0-9]+'
</source>
Manually compose an <code>apt-get purge</code> invocation of the kernels you don't want (keep the running kernel and the prior as a fallback).
<source lang="bash">
sudo apt-get -y purge linux-image-3.13.0-44-generic linux-image-3.13.0-46-generic linux-image-3.13.0-48-generic linux-image-3.13.0-55-generic linux-image-3.13.0-71-generic linux-image-3.13.0-74-generic
</source>
== RedHat and derivatives ==
There is <abbr title="Yellow Dog Updater">[[Yum]]</abbr> package manager for RedHat and derivatives. == See Also ==[[Regular Expressions]]
[[Category:System Administration]]
