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Comment on When using rsync to backup my /home folder to an external 1TB SSD, I run out of space, how??

SlurpingPus@lemmy.world ⁨10⁩ ⁨hours⁩ ago

The simplest explanation for the size difference could be if you have a symlink in your home folder pointing outside it. Idk if rsync traverses symlinks and filesystems by default, i.e. goes into linked folders instead of just copying the link, but you might want to check that. Note also that exFAT doesn’t support symlinks, dunno what rsync does in that case.

It would be useful to run ls -R >file.txt in both the source and target directories and diff the files to see if the directory structure changed. (The -l option would report many changes, since exFAT doesn’t support Unix permissions either.)

As others mentioned, if you have hardlinks in the source, they could be copied multiple times to the target, particularly since exFAT, again, doesn’t have hardlinks. But the primary source of hardlinks in normal usage would probably be git, which employs them to compact its structures, and I doubt it that you have >300 GB of git repositories.

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Wildmimic@anarchist.nexus ⁨9⁩ ⁨hours⁩ ago
A second possibility is the deduplication feature of BTRFS. If you made copies of files on your SSD, they only take up space there when changing something - thats how i keep 5 differently modded Cyberpunk 2077 installations on my drive while only taking up a fraction of space that would be needed - I wouldn’t be able to copy this drive 1:1 onto a different filesystem.

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- SlurpingPus@lemmy.world ⁨9⁩ ⁨hours⁩ ago
  Ah, I knew the mention of btrfs heebied my jeebies a little, but forgot about the CoW thing.
  
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bleistift2@sopuli.xyz ⁨9⁩ ⁨hours⁩ ago

Idk if rsync traverses symlinks and filesystems by default,

From the man page:

Beginning with rsync 3.0.0, rsync always sends these implied directories as real directories in the file list, even if a path element is really a symlink on the sending side. This prevents some really unexpected behaviors when copying the full path of a file that you didn’t realize had a symlink in its path.

That means, if you’re transferring the file ~/foo/bar/file.txt, where ~/foo/bar/ is a symlink to ~/foo/baz, the baz directory will essentially be duplicated and end up as the real directory /SSD/foo/bar and /SSD/foo/baz.

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- SlurpingPus@lemmy.world ⁨9⁩ ⁨hours⁩ ago
  Yeah, that would do it. If OP has such symlinks, they probably need to add an exception for rsync.
  
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