[rdiff-backup-users] Symlink backup error message; symlink creation times reset upon restore

[Eric Jensen]

Hi all,

I'm working with the new 1.1.11 release, and I was pleased to find that
I'm now able to perform a simple test backup from Linux to an
SMB-mounted filesystem, which doesn't allow symlinks - thanks!.  I
backed up a single directory, with both a real file and a symlinked
file.  It gave me an error:

SpecialFileError symlink_file [Errno 1] Operation not permitted

while backing up, but did properly store the file's metadata, and it
restored it as a symlink when I did a restore. 

Two questions:

1.  Should this error occur?  It appears to be backing up the data OK.
    Maybe just a warning at the beginning that the target filesystem
    doesn't support symlinks.  (At the default verbosity level, I get a
    warning about hardlinks, but not about symlinks.)  If I back up a
    larger directory, I get one of these errors for every symlink in the
    source tree.

2.  After restoring, I noted that the modification time on the symlink
    was different from the target:

Target directory:

# ls -l /root/test/test2
total 4
-rw-r--r--    1 root     root            9 Jun 20 10:38 realfile
lrwxrwxrwx    1 root     root           25 Jun 20 10:38 symlink_file -> 
/root/test/test2/realfile

Restored directory:

# ls -l /root/test/test2.restored/
total 4
-rw-r--r--    1 root     root            9 Jun 20 10:38 realfile
lrwxrwxrwx    1 root     root           25 Jun 20 10:42 symlink_file -> 
/root/test/test2/realfile


I see that the creation time on the symlink file has been changed to be
the same as the time of the restore (10:42), while the target directory
from which the backup was made has a symlink creation time of 10:38.
Looking at the file metadata, I see that there is no ModTime stored for
symlinks, only for regular files:

File realfile
  Type reg
  Size 9
  SHA1Digest 572c291421cd821a5e821e28766d0bdb719c379d
  ModTime 1182350320
  Uid 0
  Uname root
  Gid 0
  Gname root
  Permissions 420
File symlink_file
  Type sym
  SymData /root/test/test2/realfile
  Uid 0
  Uname root
  Gid 0
  Gname root
  Permissions 511


So it appears that this is simply the default behavior of rdiff-backup.
However, it strikes me that it is useful to preserve information about
when a symlink was created, and that it seems (at my very naive level of
understanding) that the infrastructure is already in place in the
rdiff-backup code, since this information is stored (and restored) for
regular files.  So perhaps this falls under the category of a feature
request, but perhaps also there's some fundamental reason not to do
this. 

Thanks as always for a fine piece of software.

Eric