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Re: Automatic debiian installation

On 7 Jun 2008, at 1:37 pm, Michael Tautschnig wrote:

[sorry for cross-posting, I guess this thread should move away from
debian-devel, but I'm not subscribed to any of the others]


I would like to use a system to install automatically all my debian pc.
i don't know wich could be the best between FAI and  PRESSEED.

Somebody could explain the difference ....

the avantage and disavantage of the two methodes...!

It depends a lot on your specific needs. If you're fine with setting whatever is debconf-configurable (be it at install time, using d-i's preseeding options, or rather at the level of the installed packages), preseeding may be an appropriate
way to go.

FAI, on the other hand, is a very flexible framework for installing systems. Debconf preseeding is supported, but just one option out of many. You might want to run several scripts for fine-tuning your system, copy over config files, etc. Flexibility comes at the cost of probably slightly higher complexity, but people
tend to get to know it quite easily.

I use both systems, in different contexts, and the above is pretty much what I'd agree with. If your requirements are fairly simple, and you're principally installing very standard workstations which don't deviate much from the default answers, then preseeding works very well. Score +1 for preseeding.

But FAI is much more flexible, and allows you to mess with pretty much any stage of the installation process in great detail. Score +1 for FAI.

It's also more complicated to set up.  Score -1 for FAI.

FAI is easier to troubleshoot - as soon as the install starts, the machine runs an ssh server, even before hard disk partitioning has happened, so you can log in and inspect what's going on (or going wrong!). Score +1 for FAI.

However, FAI usually depends on NFS -- yes, I know about fai-cd -- and so isn't very appropriate for installing machines which are not part of the same network (FAI: -1), whereas a preseeding install can easily use http or whatever to fetch its configuration information, and that's more WAN friendly (Preseed: +1). You might want to talk to the Munich guys who've done cool stuff with FAI there, including installing on wide networks.

FAI has an "update" mode, which preseeding doesn't. So if you want to update machines, you can use the same FAI config that you're using to install new machines to bring old machines up to your new standard. Of course, there are other ways to do that (cfengine, for example, which is what I use rather than FAI updates).

I think FAI works better when you have a wide variety of system configs to install, because you can define multiple classes and have machine very flexibly belong to any combination of those classes. Preseeding is rather more monolithic, and becomes hard to maintain if you don't want your machines absolutely uniform.

So there are arguments in favour of both. On balance, I prefer FAI, mainly because of easier trouble-shooting and customisation. But I happily use both.

This is all IMHO, naturally.  Your mileage may vary.


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