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Asked: 2020-10-14 11:30:32 +0800 CST

apt autoremove deleted software in use

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The first thing I realized after running apt autoremove and rebooting was that DockX no longer starts. A glance at /var/log/apt/term.log told me that the packages were indeed eradicated despite being in use right at the moment it happened:

Removing dockbarx (0.93+git20190103-1~ppa3) ...
Removing dockbarx-applet-appindicator (0.93+git20190103-1~ppa3) ...
Removing dockbarx-applet-clock (0.93+git20190103-1~ppa3) ...
Removing dockbarx-applet-hello-world (0.93+git20190103-1~ppa3) ...
Removing dockbarx-applet-volume-control (0.93+git20190103-1~ppa3) ...
Removing dockbarx-dockx (0.93+git20190103-1~ppa3) ...

My question is: Why did apt decide to remove these packages and how can I prevent this behaviour in the future?

Update

It was suggested that the packages were removed because they were dependencies of some other, already removed packages. This is not the case. I rolled back the VM anyway and now I can look at the state before the event, using dockbarx as an example:

~$ apt-rdepends -r dockbarx
Reading package lists... Done
Building dependency tree       
Reading state information... Done
dockbarx
~$

This is it. There are no packages dependent on dockbarx.

I suspect the situation is somehow related to the fact that I installed these packages from a PPA that is no longer connected. Could there be a link?

Update 2

Checked the logs manually to find out that the dockbarx package was installed as a dependency of xfce4-dockbarx-plugin, a package my system is no longer aware of - most likely because of the disconnected PPA:

~$ apt show xfce4-dockbarx-plugin
N: Unable to locate package xfce4-dockbarx-plugin
N: Unable to locate package xfce4-dockbarx-plugin
E: No packages found

Which is why apt-rdepends gives wrong output for dockbarx. Overall, the answer below is correct and I am accepting it.

This was quite a detective story.

apt 20.04

1 Answers

  1. Best Answer

    It's all about apt-marking

    Any package that is not a automatically-installed dependency (apt-marked 'auto') dependency of a specified package (apt-marked 'manual') is eligible for autoremoval.

    Example:

    sudo apt install foo bar

    • SPECIFIED packages (foo, bar) will be marked manual
    • All unspecified dependencies (libfoo1, baz) will be apt-marked auto

    Apparently, you removed whatever 'manual' package required those 'auto' dependencies.

    • Apt does not know or care that specific software is in use. It's not especially intelligent, and definitely not magical.

    In order to prevent autoremoval of a package, simply ensure that the package has an apt-marking of 'manual.'

    apt-mark showauto                    // List the packages apt-marked 'auto'
                                     // Listing does not require sudo 
                                     // It's a long list

sudo apt-mark manual <package_name>  // Change a package from 'auto' to 'manual'
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