On October 24, 2020 4:19 PM, hv@xxxxxxxxx wrote: > Hi, due to a hardware or firmware issue, my machine is currently crashing > rather a lot. If that happens around the time I'm performing any git activity, > it seems quite likely to cause substantial corruption of the git state. > > I've responded both by running sync(1) every 60 seconds and by pushing work > to github more frequently, but the latter isn't appropriate for everything; > twice recently I've lost a fair bit of work as a result. > > Q: Is there a mode in which I can run git that would make it a bit more robust > against crashes, at the cost of being a bit slower? > > > The primary symptom is that files modified shortly before a crash show up > existing but zero-length after the crash. For source files I mostly know what > to do in that situation, but `git fsck` shows a lot of files under '.git/objects' > that are empty, which seems to make things hard to recover: > > % git fsck > error: object file > .git/objects/0e/f31631726cea2e9bf89d7bbe7b924b5282d533 is empty > error: unable to mmap > .git/objects/0e/f31631726cea2e9bf89d7bbe7b924b5282d533: No such file > or directory > error: 0ef31631726cea2e9bf89d7bbe7b924b5282d533: object corrupt or > missing: .git/objects/0e/f31631726cea2e9bf89d7bbe7b924b5282d533 > [... a dozen similar entries ...] > error: object file > .git/objects/f5/a9d125645e69a0e40f9bf7a8c90b1c1c4a4ea5 is empty > error: unable to mmap > .git/objects/f5/a9d125645e69a0e40f9bf7a8c90b1c1c4a4ea5: No such file or > directory > error: f5a9d125645e69a0e40f9bf7a8c90b1c1c4a4ea5: object corrupt or > missing: .git/objects/f5/a9d125645e69a0e40f9bf7a8c90b1c1c4a4ea5 > Checking object directories: 100% (256/256), done. > Checking objects: 100% (1577/1577), done. > error: refs/stash: invalid sha1 pointer > 0000000000000000000000000000000000000000 > error: bad ref for .git/logs/refs/stash > dangling commit 1c0ea4e6159952501957012d2b9db7d68b52d107 > % > > Last time I checked out the previous state from github in a new directory and > was able to find and copy over most of my work before continuing. On this > occasion I did a `git stash save` shortly before the crash, and I'm not sure > how to get that back. I see René Scharfe's suggestion of: > git fsck --unreachable | > grep commit | cut -d\ -f3 | > xargs git log --merges --no-walk --grep=WIP from a recent message, but > that is only showing me an older stash item. I would suggest turning off write-through buffering on your disk. Let writes complete immediately instead of being deferred to sync. Also, this does feel like a disk issue, so fsck or chkdsk /f (or whatever) on your disk urgently. Good luck, Randall -- Brief whoami: NonStop developer since approximately 211288444200000000 UNIX developer since approximately 421664400 -- In my real life, I talk too much.
