On 27/06/2021 15:15, Harald van Dijk wrote:
On 26/06/2021 00:36, Harald van Dijk wrote:
Hi,
tar --exclude results in bad archives when hardlinks are used.
Consider the following:
$ mkdir tartest
$ echo hello > tartest/a
$ ln tartest/a tartest/b
$ busybox tar cf - tartest | tar tvf -
drwxr-xr-x harald/harald 0 2021-06-26 00:25 tartest/
-rw-r--r-- harald/harald 6 2021-06-26 00:25 tartest/b
hrw-r--r-- harald/harald 0 2021-06-26 00:25 tartest/a link to
tartest/b
This is okay. tar may either pick up a first and then detect b as a
hardlink to a, or pick up b first and then detect a as a hardlink to
b. On my system, it picks up b first. You can adjust the below
accordingly if on your system a is picked up first. Now, exclude b:
$ busybox tar cf - --exclude=b tartest | tar tvf -
drwxr-xr-x harald/harald 0 2021-06-26 00:25 tartest/
hrw-r--r-- harald/harald 0 2021-06-26 00:25 tartest/a link to
tartest/b
This resulted in an archive where the contents of tartest/a are
missing. Extracting the archive results in an attempt to hardlink
tartest/b, which may or may not exist in the target directory. GNU tar
does not do this, it stores the contents of the file instead, which
seems like a better idea to me. Can busybox be modified to do that as
well?
Tested with busybox 1.33.1.
It seems like the fix is trivial, please see attached patch.
ping
Cheers,
Harald van Dijk
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