Setting up CTDB on OCFS2 and VMs ...

[Michael Adam]

Hi Rowland,

I am really sorry that you are frustrated.
Pleas keep on!

We do try to document stuff, but clusters with
ctdb is still an area that is not done by
the average admin. And there are not so many
people working on the code, so as usual,
documentation sadly lacks behind.

Someone like you, who with the help of us devs
finally gets to a working system, might help
us in the end to improve the docs! :-)

Clustering also relies on a whole additional
area which is the corresponding cluster file
systems used underneath, which makes it difficult
to have comprehensive documentation for a
concrete setup.

That being said, there is documentation out
there, but not necessarily terribly up to date,
and not precisely what you want.

On the samba wiki, there is the generic but
somewhat superficial

https://wiki.samba.org/index.php/CTDB_Setup

and as a specific example the GFS/CTDB/Samba howto:

https://wiki.samba.org/index.php/GFS_CTDB_HowTo

which is of course redhat-cluster/gfs specific as
far as the file system is concerned.

The manual pages of ctdb are also pretty good by now!

It is true that Debian is especially rare in
these clustered Samba docs. This is due to
the fact, that for a long time, there was no
big focus on cluster file systems in Debian.

A couple of years ago, I have given a couple
of talks and courses about clustered Samba
partly also using Debian and Gluster, but also
RedHat and GFS. My 2010 notes

http://www.samba.org/~obnox/presentations/sambaXP-2010/sambaxp-2010-tutorial-ctdb-handout.pdf

even contain some note on what is different
and needs to be considered on a Debian systems.
(The main difference is that /etc/default is
used instead of /etc/sysconfig by most packages.)

At that time, OCFS2 was not yet ready for
CTDB/Samba, and GlusterFS was mainly available
in Debian, but did not perform very well.
Now Gluster has been taken on by RedHat, and
I think we can expect updates from that corner in the
nearer future.

Here is a paper explaining some of the
fundamentals of CTDB and the basic configuration
of CTDB and clustered samba on Top.

http://www.samba.org/~obnox/presentations/sambaXP-2009/samba-and-ctdb.pdf

And a pretty similar article from Linux Magazine:

http://www.linux-magazine.com/Issues/2009/105/Samba-for-Clusters

and an accompanying one on registry configuration:

http://www.linux-magazine.com/Issues/2009/105/Samba-s-Registry

Some of the details need to be checked because the
info is 4-5 years old, but the basics are still
correct.

As a last but possibly important remark (for those
who have not fallen asleep by now ;-) let me
mention that as far as I know, Stefan Kania
(whom I have copied in this reply, since I am not
certain that he is subscribed to the list) is currently
working on a reproducible setup with Debian/Gluster/CTDB/Samba.
Maybe he can give some insight on the specialities of
a CTDB setup on current Debian.


I apologize for having pointed mainly to my own
writings, but at the time I have undertaken some
considerable efforts to create some documentation
and explanations, so I hope this is of any use. :-)

Cheers - Michael

PS: Also, you are asking why Ronnie suggests a single node
cluster.
Because it is always good to start out with a simple case.
And once you mastered that, move on to more complicated things.
And you can even see most config points in that 1-node cluster.


On 2014-12-12 at 10:36 +0000, Rowland Penny wrote:
> On 11/12/14 18:32, ronnie sahlberg wrote:
> >I just tried building a single-node "cluster" on debian with ctdb.
> 
> Why a single node ????
> 
> >I can check building a 4 node cluster next week when I am home from my travels.
> 
> Try it with two nodes
> 
> >
> >To get ctdb running on ubuntu 14.10, as root:
> 
> Hang on, you said 'debian' above
> 
> >
> >1, Install the ctdb package:
> >apt-get install ctdb
> >
> >2, create a missing directory
> >mkdir -p /var/lib/run/ctdb
> 
> Why is there a missing directory, sounds like a bug to me.
> 
> >
> >3, remove the reclock file
> >vi /etc/default/ctdb
> >and comment out CTDB_RECOVERY_LOCK
> 
> But I want the lock.
> 
> >4, create a nodes file
> >vi /etc/ctdb/nodes
> >and add the line   127.0.0.1
> 
> Yes, but why '127.0.0.1' ???
> 
> >
> >5, create a public addresses file
> >vi /etc/ctdb/public_addresses
> >and add the two lines
> >127.0.0.2/8 lo
> >127.0.0.3/8 lo
> 
> Do you have to create these ipaddresses, if so where and how
> 
> >6, start ctdb
> >service ctdb start
> >
> 
> That is this first part I really understood.
> 
> >then check everything looks fine with 'ctbb status' and 'tail
> >/var/log/ctdb/log.ctdb'
> >
> >
> >That will not really create a very interesting cluster, just one node,
> >two public addresses and all on loopback.
> >But this should at least verify that ctdbd will start and run.
> >Then you can just shut it down and edit
> >/etc/ctdb/nodes|public_addresses and make them more interesting.
> 
> Again, why just one node. ??
> 
> >I personally suggest never running anything smaller than 4 node
> >clusters for real data.
> 
> Yes, but I am testing, so where is the documentation for people like me, who
> just want to get a couple of nodes up and running ???
> 
> Rowland
> 
> >
> >Please see
> >man ctdb
> >man ctdbd
> >less /etc/default/ctdb
> >http://ctdb.samba.org/configuring.html
> >
> >it should contain most to get started with ctdb.
> >
> >
> >regards
> >ronnie sahlberg.
> >
> >
> >
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