[rdiff-backup-users] Re: Allowing only rdiff-backup across a connection, how to set up?

[Chris G]

On Wed, Dec 23, 2009 at 11:08:50PM +0100, Giorgio wrote:
>Hi,
> 
>2009/12/23 Chris G <[1...@isbd.net>
> 
>  If I want to allow *only* rdiff backup to use an ssh link between two
>  machines what's the best way of setting it up?
> 
>There's a good howto here:
> 
>[2]http://arctic.org/~dean/rdiff-backup/unattended.html
> 
Yes, thanks, that's very useful.

-- 
Chris Green



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Re: [rdiff-backup-users] locking the rdiff-backup destination

[Jakob Unterwurzacher]

Am 2009-12-24 06:50, schrieb Alex Samad:
>>

I guess you will have to use a wrapper script for your rsync job and
your rdiff-backup job that does the locking (and obeys the lock).


yep doing something like that already, but I noticed that rdiff-backup
has a way of knowing when another riff-backup is running against the
dest, it would be could to be able to trigger that flag as well from
outside rdiff-backup


Indeed. I had not noticed that.

This is what rdiff-backup does (strace) when there is another instance 
running:


> $ strace rdiff-backup /usr/sbin /tmp/des
[...]

open("/tmp/des/rdiff-backup-data/current_mirror.2009-12-24T10:50:52+01:00.data",
 O_RDONLY|O_LARGEFILE) = 4

[...]

read(4, "PID 9157\n", 4096) = 9

[...]

kill(9157, SIG_0)   = 0
write(2, "Fatal Error: It appears that a p"..., 298
Fatal Error: It appears that a previous rdiff-backup session with process
id 9157 is still running.  If two different rdiff-backup processes write
the same repository simultaneously, data corruption will probably
result.  To proceed with regress anyway, rerun rdiff-backup with the
--force option.
) = 298


So, when you read out the PIDs from the
rdiff-backup-data/current_mirror.*
files (they contain "PID 12345"), check whether one of them is running, 
and none is, then it's safe to start rsync.


Note that
$ kill -0 PID
is somewhat unsafe as a check whether PID is running. It will return 1 
when the process does not exist but will also return 1 when the process 
exists but you don't have the permission to send a signal to it. I'd use 
ps -p.



Jakob


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Re: [rdiff-backup-users] locking the rdiff-backup destination

[Dominic Raferd]

Jakob Unterwurzacher wrote:
I guess you will have to use a wrapper script for your rsync job and 
your rdiff-backup job that does the locking (and obeys the lock).


If you start both jobs at the same machine, it's easy:
Put this at the start of each script - it will then exit when another 
instance is running.


#

#!/bin/bash

exec 200> /tmp/lockfileXYZ
flock -n 200 || echo 'Could not get lock!' && exit 1

#
Nice tip! An alternative which doesn't require flock or a temporary lock 
file is (again for a bash script):


##
#!/bin/bash

[ -n "`ps h -C rdiff-backup`" ] && echo "`basename $0` aborting - 
rdiff-backup is running" && exit 1


##

Dominic


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