bug#62379: /gnu/store/.links filling the hard drive on foreign distro

[Elias Kueny]

Hello,

I'm using guix over a foreign distro (Ubuntu 22.04). I initially installed guix 
from the Ubuntu repositories (version 1.3.0-4), and updated as user with guix 
pull (work computer: I don't have root access to run the installer script).

The problem is the size of /gnu/store/.links: after garbage collection with "guix gc 
--delete-generations=1w", /gnu/store is 17.4 GB in total, and /gnu/store/.links is 14.5 GB 
(344120 items, ranging from 93 MB to 4.1 kB each). The garbage collector prints that 
"currently hard linking saves 3717.77 MiB".
With a 40GB hard drive, the gnu store regularly fills up all the available 
space if I'm not careful. I found from an old issue 
(https://issues.guix.gnu.org/24937#1) that 10 millions links should need around 
700 MB, so this sounds like a bug.

After garbage collection, there are only 16 profiles left in 
/var/guix/profiles/per-user/ for my account: 2 for current-guix, 2 for 
guix-profile, and the rest for guix-home (where almost every program is 
installed), plus one guix shell profile I keep activated during gc to not 
uninstall it. I can't check for the root account, but I'm guessing it contains 
only the profile of the initial guix installation. There are no other users.

I tried uninstalling the original guix from the Ubuntu repositories in case the 
issue is due to some interference between it and the current guix I pulled as 
user, but /var/guix/daemon-socket/socket was gone with it, so I couldn't try to 
run the garbage collection.

Elias