Starting a FAI installation using kexec - technical thread

Henning Sprang henning at
Thu May 28 13:06:45 CEST 2009

Torsten Schlabach wrote:
> There is no FAI install kernel anymore; FAI is using a stock Debian
> kernel now, right?


> Is there mabye a FAI initrd or is the initrd also the "stock" one that
> comes from the corresponding Debian package. 

In recent FAI versions, make-fai-nfsroot creates an initrd from the
nfsroot and puts it into the tftp space.

But in very early versions(and even before, when I installed xen
paravirtual VM's via nfsroot, and the Xen DomU kernels did not contain
nfsroot support)
I've been successfull copying the normal debian initrd from /boot into
the tftp space.

> Or is my initrd which is
> used in a PXE boot generated with any special settings possibly when I
> execute make-fai-nfsroot?

As above, both should work in principle. The thing that FAI puts into
tftp dirctory might be a bit better.

> What I think my problem might come from is that in each "NFS root file
> system" howto it says "the NFS support must be statically compiled into
> the kernel". But that's definitely not the case for the stock Debian
> kernel. So I wonder if that remark in most howtos is just void today.

Yes, this is not necessary with initrd anymore.
nowadays, the initrd has scripts and necessary modules to mount the root
With initrd, the root is mounted twice anyway - first, the initrd
contents make a preliminary root filesystem that exists only in ram.
Then, the initrd scripts decide what to do depending from boot
parameters - for nfs, they load the nfs modules and mount them.

> Also quite honestly I could use some pointer to understanding that /live
> dir in the initrd which is used by FAI today ... What's in there which
> is no longer in the NFS root for example? Does the whole install run out
> of the /live dir now?

Yes, this is due to the decision to use the livehelper tools - they are
especially necessary to get the fai-cd things working, and only have the
effect on the normal network boot that the nfsroot is in that odd
location now.


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