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Re: Automatic debiian installation



I'll start by saying that preseeding is a method of automating the
standard Debian Installer. It is not an installation method on its own
right.

On Wed, Jun 11, 2008 at 11:18:17AM +0100, Tim Cutts wrote:
> 
> 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.

d-i has a shell running all the time in a different shell. There is an
optional ssh server d-i udeb if that is what you really want.

> 
> 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).

"update" is out of the scope of D-I because you have apt-get / aptitude
for that. The equivalent of "preseed" here is probably
dpkg-set-selections. Recall that in Debian after the basic debootstrap
stage of the installation, all packages are installed with basically the
same apt/dpkg code as you use on a live system.

No need to re-invent the swirl.

> 
> 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.

absolutly uniform?

preseed allows rather arbitrary (shell commands) run-time tests.

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