[Gllug] Systemimager in ssh mode

[Julian Somers]

On Wed, Feb 02, 2005 at 04:32:15PM -0000, John Hearns wrote:
> > A while back someone mentioned systemimager for cloning servers. Has
> > anyone got it working in ssh mode? I have found the documentation on
> > this a bit thin. Does it allow you to use rsa keys to authenticate the
> > clients?
> >
> > Also, does it work where clients are not on static IPs? I want to be
> > able to update lots of identical machines in the field over dialup
> > connections. I was planning to use plain old rsync over ssh, but
> > systemimager would save me the pain of a lengthy dd to install each
> > machine.
> 
> You'd be quicker posting a pre-installed hard drive.
> All joking aside, I'm being serious.
> 
> Post a hard drive.
> Post-install script to set up the networking.
> rsync back to the central site if necessary in a cron job
> 
> I assume on-site that you have a dialup connection and a router to
> a small Ethernet network?
> 
> I can't answer your question re. systemimager,
> but how about using g4u as I suggested in my post last week?
> 
> The alternative is to prepare an initrd and a linuxrc which
> a) cfdisk to partition the drive
> b) makes filesystems
> c) rsyncs from the install server (I guess you have an install server
>    at the remote site?)
> 
> dd won't work if the drive types are not similar.
> And let's face it, you won't be using the same drive for the life
> of the project.
> 

I'm not planning to do the initial setup over the air -- I'll do that
here on the LAN and send the machine -- my concern is with updates. The
machines are going on ships, so once they leave my desk, my only way to
get at them is a dvb forward channel and a satphone return channel.

I was hoping systemimager would provide a managed way of rolling out
updates over the air. But I have thought again: what if the line drops
part way through an rsync update -- lets say a kernel upgrade has been
copied over, but the modules haven't been done yet -- is there any way
to recover? 

SO my new plan is to multicast whole partition images to the machines
over the dvb connection, then trigger a script that checks & unpacks the
image and rsyncs it locally. This way I can do the whole thing
independently of the return channel, minimise expensive satphone
bandwidth, and also perhaps be able to roll back to a previous image.
(If only it were that simple I hear you say) 

Thanks for the tip on G4U -- painless cloning. Im also going to try out
partimage for this, as it does not pack empty space into the image.

thanks, 
Julain


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