XFS does use /lost+found, it calls it the "orphanage directory" and xfs_repair reparents children of corrupt directories there.

Based on comments in the kernel source, it seems like the userspace fsck for JFS and F2FS will also sometimes create /lost+found. There might be more that do.

Even with journaling, you might need one. ZeroFS [0] almost had a lost+found directory (even with the WAL enabled), because you might have consistency issues between your in-memory state and what was flushed, and especially in what order.

ZeroFS ended up not needing recovery at all through atomic, strictly ordered commits [1], but it was far from trivial (and not just a matter of requiring a WAL).

[0] https://github.com/Barre/ZeroFS

[1] https://github.com/Barre/ZeroFS/blob/main/zerofs/src/fs/writ...

Yea, run an old kernel with ext2 on a busy system writing a bunch of small files and have a power supply fail and you'll end up with something there.

fsck on large hard drives was scary on how long it could take to finish.

You need to use worse hardware and bad power :)

Same here. And I had some pretty f**ed up file systems.

At one point, I had one where the directory structure was completely broken and had circles in it (broken SSD). To be fair, in that particular case, I did not look for lost+found and just wrote a tool to extract the data manually that I was looking for.

That's what the answers are missing, of course. In some filesystem formats, it's possible either to recover completely from a journal/intent log, or at least to recover everything to the point that recovered files can be placed into the correct directory.

My SD cards have always had stuff in that folder. It scares me. I try not to look

Have to run fsck. This used to be forced about once a month but don’t remember it happening in the last decade or so.

It's a question from 2011...

they offer private instances to school too, where moderation is left to school policy, and mine seems to be good enough to use whenever i have frontend questions (i'm 10 year into my career and still use my juniors to answer my frontend questions, i think i won't ever change)

It is StackExchange. So in theory someone could modernize it at any time.

Reaching HN or other sites allows for exposure to information that a person otherwise would not ask themselves.

I also respect human responses over AI ones every day that ends in Y.

More like a FOUND.000 folder or a root directory filled with .CHK files

Not really, as it's only once per file system mount, whereas those Windows and MacOS files are sprinkled in most directories with images and almost every non-network drive directory respectively.