multiple thin client servers

[Scott Balneaves]

On Wed, Nov 22, 2006 at 11:37:32AM +0000, Gavin McCullagh wrote:
> Hi,
> 
> has any work been done or is there any documentation on how best to deploy
> multiple thin client servers.  

Work's been progressing on the Edubuntu handbook.  I'm not sure what the
status is with regards to getting it posted online.  We work on the
handbook in an SVN repository, I'm wondering if we should set up some
sort of weekly build system where the .xml files are converted to a .pdf
and posted somewhere.  I'll investigate this.

> I'm thinking in terms of if you have need
> for several thin client servers how you would:
> 
> 1. Make sure home dirs, authentication, etc. work across both servers.
> 	- nfs share home dirs?

Yes, this would be the logical way to do it.

> 	- nis for auth? ldap? 

LDAP is what we're working towards, see:

https://blueprints.launchpad.net/distros/ubuntu/+spec/edubuntu-network-auth-server

and some related specs for where we're going on the next version of
Edubuntu.

> 2. If either server went down, the other could continue to function in its
>    stead.

This is a little more difficult, because of topology:

Most people deploy LTSP workstations in the following way:

    |        ------------
   B|    eth0|          |eth1    +-----client
   A+--------+  Server1 +--------+-----client
   C|        |          |        +-----client
   K|        ------------
   B|        ------------
   O|    eth0|          |eth1    +-----client
   N+--------+  Server2 +--------+-----client
   E|        |          |        +-----client
    |        ------------

So, if Server 1 goes down, it's clients are on a private switch for that
server, and not easily moved over.  Some people handle this by having
all clients and servers on a common wire, and this works for a small
number of clients.  However, it doesn't scale well at all.

> 	- clustered dhcp/dns server?

Easily done, with 2 dhcp/dns servers

> 	- nis master/slave? ldap?

Run a master LDAP server, and run slaves on each Edubuntu server.

> 	- mirrored home dirs (ie not nfs)?

Ick. All sorts of concurrency problems.  You'd be better off making the
NFS server more robust (redundant PSU's, RAID, etc.)

> Is this sort of thing on the roadmap for Edubuntu?  I'm sure any given
> sysadmin can come up with a home-brew way to achieve most of this but it
> would be nice if Edubuntu had guidelines on it and perhaps designed the
> overall system to ease setup.  I believe ldap is in the pipeline which is
> probably a useful part of this.

Some of it is, some of it isn't.  We can always use more hands, and this
is a community effort!  The way to get the roadmap done the way you want
is to help draw the map, then roll up your sleeves and build the road.
:)

Pop by #edubuntu on irc.freenode.net.  As well, you can always create
your own specs in launchpad.

Cheers!

Scott

-- 
Scott L. Balneaves | "Let us endeavor so to live that when we come to die
Systems Department |  even the undertaker will be sorry."
Legal Aid Manitoba |    -- Mark Twain, "Pudd'nhead Wilson's Calendar"