fsck [LWN.net]

fsck

Posted Mar 20, 2007 16:02 UTC (Tue) by bronson (subscriber, #4806)
In reply to: fsck by nix
Parent article: The 2007 Linux Storage and File Systems Workshop

Unless you're an ext3 filesystem engineer, how are you supposed to know what fixes to make?? If fsck asks my mom, "1377 unreferenced nodes, delete? (Y)" (whatever a typical error looks like; it's been a while), what is she supposed to do?

The only two modes that the average Linux user can run fsck in:
- All Y, which you say is a bad idea.
- All N, in which case there's no point.

Maybe fsck could offer an "all trivial" setting, where it would automatically make fixes that it thinks are unlikely to cause data loss. If a bigger problem is found, fsck could bail out saying, "Serious errors found, back up partition before repairing!"

This is the same problem as Windows users splatting "Yes" every time their OS asks, "Do you want to allow a connection to sdlkh.phishing.org" except that the fsck questions are even less understandable!

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fsck

Posted Mar 20, 2007 17:02 UTC (Tue) by nix (subscriber, #2304) [Link]

Your points have merit: it's hard to work out which changes are safe. That's why I tend to e2fsck first with -n, and review the list to see if there are a lot of changes or they look intuitively frightening. If they do, it's image-first time, so I can retry with more n answers if fsck goes wrong.

(The `all trivial' option already exists: it's what you get if you run e2fsck with -a. If e2fsck says you must run fsck manually, that means it has nontrivial fixes to make. In my experience this is rare indeed, even in the presence of repeated power failures or qemu kills while doing rm -r.)

This is yet one more place where a CoW device-mapper layer would be useful: instead of doing huge copies, you could just do the e2fsck in a CoWed temporary image (maybe mounted on a loopback filesystem somewhere :) ) and see if that worked...