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Disk space counted twice on root folder? (lemmy.world)

submitted 5 months ago* (last edited 5 months ago) by BeatTakeshi to c/[email protected]

31 comments fedilink hide all child comments

Edit: SOLVED thanks to r00ty !

Hello, I have this weird issue that my Debian 11 will tell me the root folder is full, while I can only find files for half of the accounted space.

df -h reports 56G while the disk analyser (sudo baobab) only finds 28G.

Anyone ever encountered this? I don't have anything mounted twice.... (Not sure what udev is). Also it does not add up to 100%, it should say 7.2G left not 4.1G

df -h /dev/sda* Filesystem Size Used Avail Use% Mounted on udev 16G 0 16G 0% /dev /dev/sda1 511M 22M 490M 5% /boot/efi /dev/sda2 63G 56G 4.1G 94% / /dev/sda4 852G 386G 423G 48% /home

Edit: my mtab

Edit 2: what Gparted shows

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[–] Archr 20 points 5 months ago (1 children)

This might help in the future in case you setup a remote mount for backups in the future. Look into using systemd's automount feature. If the mount suddenly fails then it will instead create an unwritable directory in its place. This prevents your rsync from erroneously writing data to your root partition instead.

[–] BeatTakeshi 4 points 5 months ago (1 children)

Thank you for sharing this tip! Very useful indeed

[–] [email protected] 6 points 5 months ago* (last edited 5 months ago) (1 children)

You can also do the following to prevent unwanted writes when something is not mounted at /mnt/thatdrive:

# make sure it is not mounted, fails if not mounted which is fine
umount /mnt/thatdrive

# make sure the mountpoint exists
mkdir -p /mnt/thatdrive

# make the directory immutable, which disallows writing to it (i.e. creating files inside it)
chattr +i /mnt/thatdrive

# test write to unmounted dir (should fail)
touch /mnt/thatdrive/myfile

# remount the drive (assumes it’s already listed in fstab)
mount /mnt/thatdrive

# test write to mounted dir (should succeed)
touch /mnt/thatdrive/myfile

# cleanup
rm /mnt/thatdrive/myfile

From man 1 chattr:

A file with the 'i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file, most of the file's metadata can not be modified, and the file can not be opened in write mode.
Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

I do this to prevent exactly the situation you’ve encountered. Hope this helps!

[–] [email protected] 1 points 5 months ago (1 children)

I think I would have expected/preferred mount to complain that you're trying to mount to a directory that's not empty. I feel like I've run into that error before, is that not a thing?

[–] [email protected] 2 points 5 months ago (1 children)

It is with zfs, but I not with regular mount I think (at least not by default). It might depend on the filesystem though.

[–] [email protected] 2 points 5 months ago (1 children)

Ahh, that might be it. I run TrueNAS too. IMO that should be the default behavior, and you should have to explicitly pass a flag if you want mount to silently mask off part of your filesystem. That seems like almost entirely a tool to shoot yourself in the foot.

[–] [email protected] 1 points 5 months ago

Yep, it’s definitely better to have as a default