Re: [Bug-tar] Incremental restore seems to first create then rename

[Helmut Waitzmann]

"Felix E. Klee" <address@hidden> writes:

>Hi,
>
>when I try to restore an listed-incremental backup where in an
>incremental step
>
>    a directory A is to be renamed into B and a file A is to be created
>
>then I get an error message
>
>    tar: A: Cannot open: File exists.
>
>I assume that this error is caused because tar tries to create the new
>file before doing the renaming.

I assume, that tar does no renaming at all.  To know that for certain,
look at the file list of "2.tar".  The file 2store/B/a is an archive
member, and so is 2store/B, isn't it?  If tar tried to rename 2store/A
into 2store/B, there would be no need to store 2store/B/a into "2.tar".
Further, as far as I know, there is no renaming information in a tape
archive.

So, what tar tries to do is:
(1) remove the file 2store/A (which fails, because 2store/A is a directory,
    not a file),
(2) create a file 2store/A (which fails, because 2store/A exist already
    and is a directory),
(3) create a directory 2store/B and a file 2store/B/a (which successes).

>To reproduce the problem, run the attached file. Using "tar (GNU tar)
>1.14" running on Slackware 9.1, it produces the following output.
>
>    tar: 2store/a: Cannot open: File exists
(Should be "tar: 2store/A: Cannot open: File exists."  As you mentioned
already.)

This error message is caused by (2).

>    tar: Error exit delayed from previous errors
>
>Am I doing something wrong? If not, is there a workaround?

I don't know, whether option "--recursive-unlink" could help.  But
beware!  Quoting the tar info:(tar)Recursive Unlink:

   `--recursive-unlink'
        When this option is specified, try removing files and directory
        hierarchies before extracting over them.  _This is a dangerous
        option!_

      If you specify the `--recursive-unlink' option, `tar' removes
   _anything_ that keeps you from extracting a file as far as current
   permissions will allow it.  This could include removal of the contents
   of a full directory hierarchy.
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