Andrew

Thanks for this.

I dont have any comments yet - as i dont have a feel for the
subtleties, but i encoourage a discussion.

I think you ought to make a proposal to circulate, and probably
present at the Manchester meeting ?

  Pete

-----Original Message-----
From: Testbed Support for GridPP member institutes
[mailto:[log in to unmask]]On Behalf Of Andrew McNab
Sent: 12 April 2002 14:25
To: [log in to unmask]
Subject: Re: LCFG Server with Usermode Linux (fwd)


Hi,

This week we've been discussing ways to make LCFG installation easier for
small sites, and I'm forwarding my current proposal which has also gone to
WP4.

I should stress that if this is used, then initially it will be a
UK-thing, to be used by UK sites and supported by us, although CERN will
run their LCFG server in such a way that we are getting copies of an LCFG
server that actually works. However, once a site gets their "virtual" LCFG
server up and running (which should take about 6 six commands and 10
minutes) then they can call on WP4/ITeam support as normal if its contents
still don't work.



Several of the smaller sites in the UK have expressed concerns about the
effort required to set up a local LCFG server, and to update it when new
EDG releases are made. However, it is felt that if a local LCFG server is
available, then installs of CE etc will then be relatively
straightforward.

So the problem is how to provide a more automated way to install the local
LCFG server. Several options are available, but the simplest would be to
copy the disk image of an LCFG server that is known to be working (eg an
LCFG server which has been used at CERN), install this at a local site and
then modify siteconfig.h etc. If the aim is to install standard EDG
testbed releases, then this has the advantage that a consistent and
working set of LCFG software files and EDG RPM's are obtained in one step.

However, there are obvious problems with transporting and installing disk
images to other sites, largely because of the need to match hardware
device drivers, which is increasingly a problem as the new and cheaper
hardware used by small sites isn't supported by RedHat 6.2.

One solution to this is to use the Usermode Linux system, which allows you
to run a virtual Linux machine within another Linux host. The virtual
machine uses a special kernel which can be run from the command line as a
user process (hence "Usermode Linux") and which intercepts system calls
and appropriately translates them into system calls to the host machine.

Disks are provided to the virtual machine as large disk image files, and
the project provides disk images for a variety of Linux distributions,
including several for RedHat 6.2 and 7.2.

User mode Linux supports (virtual) network interfaces on the virtual
machines, and these can be given routable IP numbers and be made
accessible to the local ethernet by routing through the host. (Indeed,
some people are using User Mode Linux to provide "jailed" DNS and Mail
servers.)

With this in place, we could install the LCFG server in a virtual machine,
with full network access and then be able to copy its disk image to other
sites, who would in turn use it inside a virtual machine.

This has a number of advantages for small sites:

1) They start from an LCFG server that definitely works, including any
   steps which are not yet documented.
2) They get a consistent set of RPM's to install on the CE etc.
3) They don't have to dedicate one machine as an LCFG server.
4) They can use whatever version of Linux they need to support the
   hardware of the host machine - ie they can use recent, cheap hardware
   not supported by RH6.2.

The disadvantage in that the disk images will be large (~GB) should not
be a problem if this is intended for small sites which only aim to track
major EDG releases.

Additionally, this tool would provide a powerful way for developers to
test components which communicate over the network between different
machines (eg you could install complete virtual CE and SE's on your
development machine.) Having LCFG disk images available to set up a local
LCFG server, from which to install the virtual machines, would be a first
step in doing this.

For more details of User Mode Linux, please see
 http://user-mode-linux.sourceforge.net/

Cheers,

 Andrew