[drbd-mc] debian-style config with dmc

Rasto Levrinc rasto.levrinc at linbit.com
Thu Dec 30 08:17:46 CET 2010

On Thu, December 30, 2010 1:44 am, Peter Beck wrote:
> Hi guys,
> I am using Debian (Squeeze) and I've just downloaded DMC 0.8.6.
> The DRBD config files on Debian are stored in /etc/drbd.d/
> and the /etc/drbd.conf just links to this directory:
> drbd.conf:----8<--------8<--------
> include "drbd.d/global_common.conf"; include "drbd.d/*.res";
> ----8<--------8<--------8<--------
> DMC will replace this config with its own config including all
> resources. Will this change to work with "debian-style" in future releases
> ?

It works with "debian-style" configs. It was actually introduced in DRBD
couple of months ago. As you will see later, this not as big problem as it
seems, but it can create an endless confusion. It is a known problem.

Here's what happens: drbdadm parses the config and creates an XML, that
GUI like DRBD MC can use. In this XML all the DRBD config is present, but
the on-disk layout of config files is lost. As you save the config in the
GUI. the small drbd.conf with include directives is overwritten with a big
config with all the resources without the include directives.

So nothing is lost, only there are files laying around that are not
included and an admins that write configs by hand may not notice it and
modify not used config files, etc.

There are couple of solutions to this, but none of them is good:

1. DRBD MC can parse the config from disk, instead of getting XML config
from drbdadm. To reimplement the parser in the GUI would be very
impractical and another moving target, that should be avoided if possible.

2. Leave it like it is. It works, but it can hit some people, like it did
hit you.

3. DRBD MC can create a modular layout by default, with a file per
resource and small drbd.conf with include directives, but that could again
leave some unincluded files laying around and create an endless confusion.
It also creates problems with DRBD config backup.

I am tending to the 3. option, but if somebody has 4., I am all ears. :)


: Dipl-Ing Rastislav Levrinc
: DRBD MC http://oss.linbit.com/drbd-mc/
: DRBD/HA support and consulting http://www.linbit.com/
DRBD(R) and LINBIT(R) are registered trademarks of LINBIT, Austria.

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