[PLUG] When mounted doesn't mean mounted

Michael M. Moore michael at writemoore.net
Thu Jun 25 02:02:32 UTC 2009


On Wed, 2009-06-24 at 18:01 -0700, John Jason Jordan wrote:
> 
> I found the man page overwhelming, and the wiki and FAQ equally so. The
> problem is that they assume more knowledge of how commands and
> filesystems work than I have. 
> 
> However, I have concocted the following which I think will back up
> everything to the disk in the Ultrabay (assume all one line):
> 
> rdiff-backup
> 	--exclude /proc
> 	--exclude/ media
> 	--exclude /mnt
> 	--exclude /tmp
> 	--exclude /home/jjj/.gvfs
> /
> /media/disk2/Full_system_backup/
> 
> The above is to be run after I verify that disk2 is really mounted. And
> the folder /Full_system_backup exists.

Yes, I think, but it would be easier if you just fired up gedit and
typed:

- /proc
- /media
- /mnt
- /tmp
- /home/jjj/.gvfs

Save that file as whatever.txt (or ~/Documents/whatever.txt -- wherever
you want to put it).  Then run:

rdiff-backup
--include-globbing-filelist /home/jjj/Documents/whatever.txt 
/ /media/disk2/Full_system_backup

(Again, all on one line.)

But, whatever you want.

> Issues that I am unclear about:
> 
> 1) What if /Full_system_backup already exists and contains a previous
> backup?
> 2) How do I make an incremental backup?
> 

rdiff-backup will make an incremental backup by default.  The first time
you run it, it creates the backup, which is an exact copy of everything
you want to backup.  The second time you run it, it makes an incremental
backup -- that is, it only copies the data that has changed since the
first time you ran it.  The third time you run it, it makes another
incremental backup -- only copies that data that has changed since the
second time you ran it.  And so on.

Eventually you will most likely want to delete some of the older
increments.  You do that by running:

rdiff-backup --remove-older-than 1W /media/disk2/Full_system_backup

(That will remove increments older than one week.  You can remove older
than one year, two months, three days, four hours, whatever.  Adjust the
"1W" as you wish.)

> It seems to me that the real power of rdiff-backup is to make
> incremental backups which can be treated as full backups because they
> contain links to files in previous backups when the files have not
> changed. Thus, assuming my understanding is correct, I should make one
> full system backup, and thereafter only incremental backups. Another
> full system backup should never be necessary. Or have I misunderstood
> that?

Nope, no misunderstanding.  That's how it works.

> And, 3) How do I make sure that it will back up to the disk in the
> Ultrabay and not to the mount point?

By making sure you specify the correct path.  If your Ultrabay is
mounted on /media/disk2 and you have
created /media/disk2/Full_system_backup ... then your command will be
fine.  If your Ultrabay is mounted somewhere else, then rdiff-backup
will fail with:

Fatal Error: Could not begin backup due to
[Errno 2] No such file or directory: '/media/disk2/Full_system_backup'

I just tried it here, just to confirm, without my external hard drive
mounted, and I got that error.  I really don't understand what happened
before, with pybackpack, because I know rdiff-backup won't just move
your backup someplace else if it can't backup to the directory you
indicated.  Instead, it will fail ... which, IMO, is the correct
behavior.  

-- 
Michael M.




More information about the PLUG mailing list