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]
>
>> Hello,
>>
>> I would like to use a system to install automatically all my debian
>> pc.
>> But
>> 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.
Tim
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