Disk space required for installation is larger than the one freed after removal: why?

Question

I installed OBS Studio:

sudo apt-get install obs-studio 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  gir1.2-keybinder-3.0 libkeybinder-3.0-0
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  libfdk-aac0 libluajit-5.1-2 libluajit-5.1-common libxcb-xinerama0
The following NEW packages will be installed:
  libfdk-aac0 libluajit-5.1-2 libluajit-5.1-common libxcb-xinerama0 obs-studio
0 upgraded, 5 newly installed, 0 to remove and 0 not upgraded.
Need to get 3,678 kB of archives.
After this operation, 13.0 MB of additional disk space will be used.
Do you want to continue? [Y/n]

I decided to remove it:

sudo apt-get --purge remove obs-studio Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  gir1.2-keybinder-3.0 libfdk-aac0 libkeybinder-3.0-0 libluajit-5.1-2
  libluajit-5.1-common libxcb-xinerama0
Use 'sudo apt autoremove' to remove them.
The following packages will be REMOVED:
  obs-studio*
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 11.6 MB disk space will be freed.
Do you want to continue? [Y/n]

When removing it, I expect 13.0 MB of disk space to be freed because that is what the installation required, but I got 11.6 MB disk space freed instead: Why?

Melebius · Accepted Answer · 2018-05-22T17:28:45.203

5

The difference can be found here:

The following additional packages will be installed:
  libfdk-aac0 libluajit-5.1-2 libluajit-5.1-common libxcb-xinerama0

After you uninstall obs-studio, these packages should be available to remove using apt-get autoremove if no other packages depend on them.

You could also run:

sudo apt-get remove --purge obs-studio libfdk-aac0 libluajit-5.1-2 libluajit-5.1-common libxcb-xinerama0

and you should get the original size directly.

edited May 22 '18 at 17:28

answered May 22 '18 at 17:27

Melebius

11,121
8
50
77

I think you are right. I run `autoremove` and 1 477 KB more were freed – Billal Begueradj May 22 '18 at 17:28

score 4 · Answer 2 · edited May 23 '18 at 05:49

Because not everything gets removed. Notice that the package requires couple libraries installed among which libluajit-5.1-2. During uninstallation only the package itself is removed, and you’re prompted to use autoremove to get rid of unused other packages. Re-read the uninstallation prompt again. Config files also may not get removed. For full removal sometimes --purge option is advised.

As for why that's done so, I can only guess it's a protective feature, as various software relies on libraries and APIs, so promoting system admin to remove them manually is a sanity check that it's exactly what they want. Or in other words, avoiding breaking things just in case.

Thank you for the "deeper" explanation (you got my upvote) – Billal Begueradj May 22 '18 at 17:47 — Billal Begueradj, May 22 '18 at 17:47

Disk space required for installation is larger than the one freed after removal: why?

2 Answers2