this post was submitted on 08 Oct 2025
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(SOLVED) Where did all my space go? (lemmy.world)
submitted 2 weeks ago* (last edited 1 week ago) by Jozzo@lemmy.world to c/linux@lemmy.ml
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Edit: Solved!

Unfortunately I'm not sure exactly what fixed it, because I was running btrfs commands like a madman. Some combination of the following caused my 100GB labelled as UNREACHABLE to turn into UNUSED, which allowed that space to be written to as normal:

sudo btrfs balance start -v /

sudo btrfs filesystem defrag -v /

sudo btrfs filesystem defrag -v -r /

Also the tool btdu was incredibly helpful!

One of my linux boxes ran out of disk space, which surprised me, because it definitely didn't have that much stuff on it. When I check with df it says I have used 212GB on my / path:

$ df -h /
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       227G  212G  5.2G  98% /

So, I tried to use du to see if maybe a runaway log file was the cause, but this says I have only used 101GB on my / path (this is also more in-line with how much space I expected to be used):

$ du -h | sort -h
...
101G    /

Using those commands with sudo outputs the same sizes.

My filesystem is Btrfs, I've tried the suggestion to use btrfs balance start ... but this actually INCREASED my disk usage to 99% lol

So my question is... what on earth is using the remaining 111GB?? Why can I not see it in du?

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[–] danielquinn@lemmy.ca 6 points 2 weeks ago* (last edited 2 weeks ago) (2 children)

The bit of information you're missing is that du aggregates the size of all subfolders, so when you say du /, you're saying: "how much stuff is in / and everything under it?"

If you're sticking with du, then you'll need to traverse your folders, working downward until you find the culprit folder:

$ du /*
(Note which folder looks the biggest)
$ du /home/*
(If /home looks the biggest)

... and so on.

The trouble with this method however is that * won't include folders with a . in front, which is often the culprit: .cache, .local/share, etc. For that, you can do:

$ du /home/.*

Which should do the job I think.

If you've got a GUI though, things get a lot easier 'cause you have access to GNOME Disk Usage Analyzer which will draw you a fancy tree graph of your filesystem state all the way down to the smallest folder. It's pretty handy.

[–] Jesus_666@lemmy.world 9 points 2 weeks ago

GUI disk space analyzers are absolutely amazing.

For those who prefer KDE and/or donut graphs, Filelight has you covered.

[–] Duke_Nukem_1990@feddit.org 4 points 2 weeks ago

Bookmarked! Thanks!