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Playing with e2fsprogs debugfs, by change/accident, a file named filen/ame was created. Obviously the forward slash character / serves as the special separator character in pathnames.

Still using debugfs I wanted to remove the file named filen/ame, but I had little success, since the / character is not interpreted as part of the filename?

Does debugfs provide a way to remove this file containing the slash? If so how?

I used:

cd /tmp
echo "content" > contentfile
dd if=/dev/zero of=/tmp/ext4fs bs=1M count=50
mkfs.ext4 /tmp/ext4fs
debugfs -w -R "write /tmp/contentfile filen/ame" /tmp/ext4fs
debugfs -w -R "ls" /tmp/ext4fs

which outputs:

debugfs 1.43.4 (31-Jan-2017)
 2  (12) .    2  (12) ..    11  (20) lost+found    12  (980) filen/ame

I tried the following to remove the filen/ame file:

debugfs -w -R "rm filen/ame" /tmp/ext4fs

but this did not work and only produced:

debugfs 1.43.4 (31-Jan-2017)
rm: File not found by ext2_lookup while trying to resolve filename

Apart from changing the content of the directory node manually, is there a way to remove the file using debugfs ?

Toby Speight
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humanityANDpeace
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  • Does escaping the forwardslash (`filen\/ame`) not work? – JAB Mar 20 '17 at 18:00
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    +1, and congratulations. You've managed to find one of the only two cases of "weird character in file name" where just correctly quoting and/or escaping the character in a shell command won't solve the problem. (The other one would be a null byte in a file name, although I suspect that, on most filesystems, that would just truncate the name.) – Ilmari Karonen Mar 20 '17 at 18:22

3 Answers3

32

If you want a fix and are not just trying out debugfs, you can have fsck do the work for you. Mark the filesystem as dirty and run fsck -y to get the filename changed:

$ debugfs -w -R "dirty" /tmp/ext4fs
$ fsck -y /tmp/ext4fs
 ...
/tmp/ext4fs was not cleanly unmounted, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Entry 'filen/ame' in / (2) has illegal characters in its name.
Fix? yes
 ...
$ debugfs -w -R "ls" /tmp/ext4fs
2  (12) .    2  (12) ..    11  (20) lost+found    12  (980) filen.ame
meuh
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3

Congradulations on fsck working; if for some reason it didn't work the answer is ls -i1 followed by umount and then clri.

Ref: http://docstore.mik.ua/orelly/unix/upt/ch23_13.htm

I have actually tested this method.

Joshua
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  • If this is Linux (which it seems like), it's worth noting that `clri` isn't a separate command (as it is on some other Unix systems), it's a subcommand inside `debugfs`. – hobbs Mar 20 '17 at 18:45
  • @hobbs: must make mine unusual then. Oh wait, nvm clri was just echo "clri $2" | debugfs "$1" – Joshua Mar 20 '17 at 18:50
  • Your instructions require running fsck anyway - which will fix the problem, with the message `Entry 'filen/ame' in / (2) has deleted/unused inode 12. Clear?` instead of the one noted in the other answer - but doing the clri is an extra step. There doesn't seem to be a way to resolve this purely from within debugfs. – Random832 Mar 20 '17 at 18:54
  • @Random832: I had fsck not fix it of its own in ages past. :( – Joshua Mar 20 '17 at 18:56
-1

If you move the file to a directory, you can then delete the directory with the file in it.

mkdir foo 
mv filen* foo
rm -rf foo
Sebastian
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carl
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    This would work for any _other_ awkward filename, but it won't work for a filename that has `/` in it. – zwol May 07 '18 at 20:08