Re: cross-subvolume cp --reflink

["Norbert Scheibner" <scno@gmx.net>]

> On: Sun, 01 Apr 2012 19:45:13 +0300 Konstantinos Skarlatos wrote

> > That's my point. This poor man's dedupe would solve my problems here
> very well. I don't need a zfs-variant of dedupe. I can implement such a
> file-based dedupe with userland tools and would be happy.
> 
> do you have any scripts that can search a btrfs filesystem for dupes 
> and replace them with cp --reflink?

Nothing really working and tested very well. After I get to known the missing cp --reflink feature I stopped to develop the script any further.

I use btrfs for my backups. Ones a day I rsync --delete --inplace the complete system to a subvolume, snapshot it, delete some tempfiles in the snapshot.
In addition to that I wanted to shrink file-duplicates.

What the script should do:
1. I md5sum every file
2. If the checksums are identical, I compare the files
3. If 2 or more files are really identical:
   - move one to a temp-dir
   - cp --reflink the second to the position and name of the first
   - do a chown --reference, chmod --reference and touch --reference
     to copy owner, file mode bits and time from the orginal to the
     reflink-copy and then delete the original in temp-dir

Everything could be done with bash. Thinkable is the use of a database for the md5sums, which could be used for other purposes in the future.