this post was submitted on 08 Oct 2025
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(SOLVED) Where did all my space go? (lemmy.world)
submitted 4 days ago* (last edited 1 day 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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[–] utopiah@lemmy.ml 23 points 4 days ago* (last edited 4 days ago) (1 children)

I typically investigate with ncdu which gives very useful visualization like :

***
/home/fabien/Prototypes/esphome/.esphome ----------------------------------------------------------------------------------------------------------------
                                     /..
    3.1 GiB [######################] /platformio
  218.1 MiB [#                     ] /build
   28.0 KiB [                      ] /idedata
    8.0 KiB [                      ] /storage

and let's you iterate. Here for example you'd go into platformio and get another view, press d to delete files or directories that aren't needed anymore if it's a stale project e.g. node_modules. Go back, etc.

So yes, warmly recommended, both on desktop and remote servers. It's way easier IMHO that du -sh ./directory then cd, rinse and repeat. It's also way WAY faster then GUI equivalents ... because you navigate and take action, e.g. delete, with your keyboard.

All that being said, if it's about your filesystem rather than your files, it probably won't help much. I don't know enough about btrfs to help unfortunately.

[–] Jozzo@lemmy.world 6 points 4 days ago

ncdu

Oh this one is very cool! Unfortunately it also only shows the same 101GB being used:

ncdu 1.22 ~ Use the arrow keys to navigate, press ? for help                                                                                                                                  
***
/ ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   93.1 GiB [###########################] /home                                                                                                                                               
    6.5 GiB [#                          ] /usr
  790.4 MiB [                           ] /var
  173.0 MiB [                           ] /boot
   12.8 MiB [                           ] /etc
    1.7 MiB [                           ] /root
    1.3 MiB [                           ] /run
   44.0 KiB [                           ] /tmp
@   4.0 KiB [                           ]  initrd.img.old
@   4.0 KiB [                           ]  initrd.img
@   4.0 KiB [                           ]  vmlinuz.old
@   4.0 KiB [                           ]  vmlinuz
@   4.0 KiB [                           ]  lib64
@   4.0 KiB [                           ]  sbin
@   4.0 KiB [                           ]  lib
@   4.0 KiB [                           ]  bin
.   0.0   B [                           ] /proc
    0.0   B [                           ] /sys
    0.0   B [                           ] /dev
    0.0   B [                           ] /media
e   0.0   B [                           ] /srv
e   0.0   B [                           ] /opt
e   0.0   B [                           ] /mnt