[Savannah-hackers-public] [task #10898] Special treetment for symlinks and special files needed

[anonymous]

URL:
  <http://savannah.gnu.org/task/?10898>

                 Summary: Special treetment for symlinks and special files
needed
                 Project: Savannah Administration
            Submitted by: None
            Submitted on: Mi 26 Jan 2011 01:20:32 UTC
         Should Start On: Mi 26 Jan 2011 00:00:00 UTC
   Should be Finished on: Mi 26 Jan 2011 00:00:00 UTC
                Category: None
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

- Symlinks should be compared by readlink instead of comparing the target
files.
- Special files such as device files should be compared by checking the major
/ minor number
- fifos ...
- have I forgotten something ?

Yes, I know, that this can not be used for creating patches, but diff is not
only used for creating patches. ;-)

The special handling could be optional, activated by command line switches.

Use case:

As a person still learning to work with GNU/Linux, I sometimes create a clone
copy of my system partition on another partition before doing large
configuraiton changes in order to have a bootable backup system in the old
state.
After copying (I always do this using a live CD), I would like to verify the
copied data using diff. Yes, I already experienced a few turned bits during
copying. Since that, I never copy large amounts of data without verifying
anymore.

I also would like to use diff for analyzing the differences between the
reconfigured and the backup system, especially if the reconfiguration crashes
it :-)
That's the second reason why I don't use tar for backup.

And here comes the problem:

All the symlinks and all the special files produce so many diff errors that
it is really hard (if not impossible) to see the real differences.
The errors in the symlinks occur because I do the diff in the live system,
too. So, every symlink that points to something starting with / is broken
because the mount points of the / partition is something like /mnt/system1
while in the live sysstem. Comparing symlinks via readlink just would not care
for that.

And you never can check for a changed symlink (would be especially useful for
/etc/alternatives) or a device major/minor number.

It would be extremely helpful to me to have a --no-dereference and a
--special-files switch.

Thanks and Regards ...




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