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Of late, I've done a lot of configuration changes on my Trusty laptop (14.04 LTS). Firstly, I installed gnome-shell, did all updates and migrated to the LTS enablement stack. After that, I added the gnome 3 staging ppa and upgraded gnome-shell from v3.10 to v3.12 from there. Now, when I run apt-get autoremove, I get these packages in the list:

The following packages were automatically installed and are no longer required:
  evolution-indicator gdm gir1.2-gkbd-3.0 gir1.2-tracker-0.16 gir1.2-xkl-1.0 libgtksourceview2.0-0
  libgtksourceview2.0-common libiptcdata0 libtracker-extract-0.16-0
  libtracker-miner-0.16-0 libtracker-sparql-0.16-0 linux-headers-4.2.0-23
  linux-headers-4.2.0-23-generic linux-image-4.2.0-23-generic
  linux-image-extra-4.2.0-23-generic python-gtksourceview2

As I understand, gdm is a critical package which is very much needed as I'm using the gnome-shell. I've also looked at this answer which suggests marking a package as "needed" by just running apt-get install <package>. But how do I know which packages of this list I can safely remove without affecting my system? I know for a fact, however, that I don't need linux-image-* and linux-headers packages as I've already upgraded to later kernel versions. But how do I know about the rest of the packages?

Community
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Prahlad Yeri
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  • maybe gdm was replaced by another displaymanager....same for me, when upgrading my ubuntu....lightdm was used instead of gdm... – Ben Jan 25 '16 at 07:47
  • I can understand gdm, but what about the other bunch of packages? Maybe I should edit the title because the issue is about all the extra packages, not just gdm. – Prahlad Yeri Jan 25 '16 at 07:50
  • looks like the automatically installed packages are not needed anymore...there are none references (from any installed package) to it anymore.So, you should be safe. (you could reinstall the removed packages when you have problems) – Ben Jan 25 '16 at 07:54
  • @Ben But how do I absolutely and certainly know that I can just remove them? Like gdm, what if any of those are critical packages? – Prahlad Yeri Jan 25 '16 at 07:55
  • Write down the removed packages and remove them...when you have problems, reinstall them. – Ben Jan 25 '16 at 07:58
  • @Ben Is there no way to find the dependency? The critical apps I use are many like firefox, thunderbird, geany, etc. How can I know if any of them depends on these packages directly or indirectly? – Prahlad Yeri Jan 25 '16 at 08:07
  • When all your installed packages are installed/managed by the package-manager, all references / dependencies should be automatically checked.Anyway, you could just re-install them, when you have problems. – Ben Jan 25 '16 at 08:10

1 Answers1

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the command apt-cache showpkg <package> will tell you the packages "reverse depends" i.e. what other packages - in your configured repositories (not necessarily installed packages) - depend on that package.
In the case of gdm there are alot, so I wrote this script to iterate through all of the reverse dependencies to check if any were installed - which would indicate that you probably shouldnt remove gdm. 

#!/bin/bash

package=$1

apt-cache showpkg $package | sed '1,/Reverse Depends:/d;/Dependencies:/,$d'  > /tmp/dependencies.txt

while read line
do
    reverse_dependency=$(awk -F '[:,]' '{print $1}' <<< $line)
    if dpkg -s $reverse_dependency &> /dev/null
    then
        echo "$line is installed and depends on $package"
    fi
done < /tmp/dependencies.txt

If you invoke the script you need to pass the package as a parameter i.e.

./script "gdm"

On my machine the result was

$ ./script.sh gdm
plymouth:i386,gdm 3.0.4-0ubuntu11 is installed and depends on gdm
plymouth,gdm 3.0.4-0ubuntu11 is installed and depends on gdm
plymouth:i386,gdm 3.0.4-0ubuntu11 is installed and depends on gdm
plymouth,gdm 3.0.4-0ubuntu11 is installed and depends on gdm
the_velour_fog
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  • Thanks a lot for this script! When I pass gir1.2-gkbd-3.0 as parameter, I get gnome-shell is installed and depends on gir1.2-gkbd-3.0. Does that mean removing this simple package will remove the gnome-shell ? – Prahlad Yeri Jan 25 '16 at 15:43
  • no it means if you remove gir1.2-gkbd-3.0 you will break the gnome-shell package. that was your basic question right if I remove a package will my system break? I probably should have mentioned, if the script produces no output it means there is nothing installed on your conputer that uses the package you passed as a parameter - and theorectically you can remove it and your system would be ok – the_velour_fog Jan 25 '16 at 19:00
  • Okay. So, if I remove gir1.2-gkbd-3.0, the gnome-shell package might break, but my system will not, right? Or do I need to worry about some gnome application depending on that package being intact? My basic question was "whether my system will break or not by removing these packages?" But as I understand it is only the package that might break, not the gnome desktop system, right? – Prahlad Yeri Jan 25 '16 at 19:05
  • If other apps/packages or the desktop depend on gnome-shell and you break gnome-shell by removing a dependency, then yes you could risk breaking things. an automatically installed package is one that apt/dpkg installed "behind the scenes" because another package needed it. however if you remove the original package the automatically installed packages dont get removed - you get the message you have been getting and you have to run apt-get autoremove yourself. – the_velour_fog Jan 25 '16 at 19:24