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Author: Olaf Meeuwissen
To: Florian Zieboll
CC: dng
Subject: Re: [DNG] Advice to migrate from Beowulf to Chimaera
Hi Florian, Alessandro,

Florian Zieboll via Dng writes:

> On Mon, 19 Apr 2021 13:10:49 +0200
> Alessandro Vesely via Dng <dng@???> wrote:
>> Isn't there a way to remove
>> packages not used for more than one year?
> Definitely not an approach for automated package removal, but perhaps a
> valid starting point for decluttering manually:
> $ find /usr/bin -atime +360 | xargs -l1 apt-file find | sort

I hadn't thought of that approach but rather than look at use (for some
definition of use), I like to use apt-mark and a judicious set of APT
options to keep my systems free of stuff I don't need.

That goes a bit like this

sudo apt-mark auto $(apt-mark showmanual)

followed by looking at what

sudo apt auto-remove

would like to get rid of. Make sure to say 'n'!
Based on the list of potential removals, I

sudo apt-mark manual <list packages I want to keep>

After iterating a couple of times until I'm happy with the list of stuff
that will be removed I finally say 'y' so apt zaps the stuff I don't

The first time around, there will be quite a long list of packages that
are candidates for removal. Even without a desktop environment
installed the list can be several tens of packages. Look for the
"top-level" kind of packages to `apt-mark manual`, things like
task-xfce-desktop, so you don't have to add a long list of packages.
You can `apt-mark auto` them later and fine-tune your list of manually
installed packages.

# This is how I whittle down the list of xserver-xorg-video-* packages
# that I really need :-)

Doing this in phases also gives you a bit of an opportunity to recover
from mistakes when you remove a package you actually need without
realizing it. Check the /var/log/apt/history.log* files to see what you
removed recently if stuff breaks.

Options that you might want to pass to that apt auto-remove invocation

-o APT::AutoRemove::SuggestsImportant=false
-o APT::AutoRemove::RecommendsImportant=false
-o APT::Get::Purge=true

# Add them to /etc/apt/apt.conf if you want to use these by default.

The first is pretty benign. It just removes those packages that are
only kept installed because some package has a Suggests: dependency on
it. Of course, you might want to keep it. In that case, just say

sudo apt-mark manual <package you want to keep>

The second option is similar but ups the ante a bit and tries to get rid
of packages that are only installed because they are recommended. As
for the Suggests:, use apt-mark manual to keep stuff you want/need and
get rid of the rest.

The third and final option makes sure any configuration files are
removed as well. I keep mine version controlled with etckeeper so
zapping config files is typically not an issue for me. The git repo has
a copy that I can resurrect as needed. If you do not have backups of
configuration files that might be removed, you're probably better of not
using this option.

Hope this helps,
Olaf Meeuwissen, LPIC-2            FSF Associate Member since 2004-01-27
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