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.
Cheers,
Harald van Dijk
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