Re: Bug in handling hard links in bind-mounted directories

[Sergey Poznyakoff]

Hi Derec,

> It appears that tar doesn't always recognize (and treat as hard links) files
> that are the same file, but appear in two different directories from bind
> mounts.
>
> $ sudo mount -o bind /tmp/foo/bar /tmp/foo/baz
> $ echo "test data" >/tmp/foo/bar/bleh
> $ stat --printf "%d %i %n\n" /tmp/foo/bar/bleh /tmp/foo/baz/bleh
> 51 97105 /tmp/foo/bar/bleh
> 51 97105 /tmp/foo/baz/bleh

Tar uses link count to decide whether a file might be a hard link to
another file.  In this test case, link count of bleh is 1, so it skips
hardlink detection phase.  To force hardlink detection, use the -h
(--dereference) option:

   tar -hcf /tmp/testing.tar /tmp/foo

Regards,
Sergey