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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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112

non-Euclidean filesystem (lemmy.world)

submitted 7 months ago* (last edited 7 months ago) by qaz@lemmy.world to c/linux@lemmy.ml

38 comments fedilink hide all child comments

I noticed that I only had 5 GiB of free space left today. After quickly deleting some cached files, I tried to figure out what was causing this, but a lot was missing. Every tool gives a different amount of remaining storage space. System Monitor says I'm using 892.2 GiB/2.8 TiB (I don't even have 2.8 TiB of storage though???). Filelight shows 32.4 GiB in total when scanning root, but 594.9 GiB when scanning my home folder.

Meanwhile, ncdu (another tool to view disk usage) shows 2.1 TiB with an apparent size of 130 TiB of disk space!

    1.3 TiB [#############################################] /.snapshots
  578.8 GiB [####################                         ] /home
  204.0 GiB [#######                                      ] /var
   42.5 GiB [#                                            ] /usr
   14.1 GiB [                                             ] /nix
    1.3 GiB [                                             ] /opt
. 434.6 MiB [                                             ] /tmp
  350.4 MiB [                                             ] /boot
   80.8 MiB [                                             ] /root
   23.3 MiB [                                             ] /etc
.   5.5 MiB [                                             ] /run
   88.0 KiB [                                             ] /dev
@   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 [                                             ] /srv
    0.0   B [                                             ] /mnt

I assume the /.snapshots folder isn't really that big, and it's just counting it wrong. However, I'm wondering whether this could cause issues with other programs thinking they don't have enough storage space. Steam also seems to follow the inflated amount and refuses to install any games.

I haven't encountered this issue before, I still had about 100 GiB of free space last time I booted my system. Does anyone know what could cause this issue and how to resolve it?

EDIT 2024-04-06:

snapper ls only shows 12 snapshots, 10 of them taken in the past 2 days before and after zypper transactions. There aren't any older snapshots, so I assume they get cleaned up automatically. It seems like snapshots aren't the culprit.

I also ran btrfs balance start --full-balance --bg / and that netted me an additional 30 GiB's of free space, and it's only at 25% yet.

EDIT 2024-04-07: It seems like Docker is the problem.

I ran the docker system prune command and it reclaimed 167 GB!

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[–] maiskanzler@feddit.de 63 points 7 months ago (1 children)

Your btrfs snapshots are possibly counted separately by all the regular tools. They simply go into every directory they can find and add up the size of the files they see. They do not care if they are looking at an identical snapshot of the folder next to them, they simply add it all up.

Use sudo btrfs filesystem show (and maybe add a path behind it, I am not sure). That will give you the true usage.

[–] qaz@lemmy.world 26 points 7 months ago (1 children)

sudo btrfs filesystem show seems to display a reasonable amount.

Label: none  uuid: af5f864d-2de9-48a9-b521-5923dc08c9e3
        Total devices 1 FS bytes used 867.13GiB
        devid    1 size 922.12GiB used 921.12GiB path /dev/mapper/system-root

[–] friend_of_satan@lemmy.world 28 points 7 months ago* (last edited 7 months ago)

This makes sense. When you use a copy-on-write block device, it is doing things below the level of the filesystem, so you have to use cow-aware tools to get an accurate view of your used disk space. For example, if you have two files that are 100% deduplicated at the cow-block level, they would show up as different inodes on the filesystem and would appear as using twice the space in the filesystem as they do on the block device. Same would go for snapshots and compressed blocks.