Use of /dev/disk/by-path/... in disk_config?

[Steffen Grunewald]

Hi,

On Thu, 2018-01-18 at 16:23:03 +0100, Thomas Lange wrote:
> >>>>> On Thu, 18 Jan 2018 16:08:32 +0100, Steffen Grunewald <steffen.grunewald at aei.mpg.de> said:
> 
>     > Talking about "path" - is there a trick to get multipath-tools installed
>     > in the nfsroot? All my attempts fail due to initramfs not cooperating 
>     > with dracut.
> Just add the packages to /etc/fai/NFSROOT. Then they will be
> installed into the nfsroot when you recreated the nfsroot.

This didn't work, I tried multiple times (and learned my lesson not to
create a new nfsroot as long as there are machines mounting the old one).

With a nfsroot otherwise functional, I've chroot-ed inside, and
"apt-get -s install multipath-tools" offers the following:

Reading package lists...
Building dependency tree...
Reading state information...
The following additional packages will be installed:
  initramfs-tools initramfs-tools-core klibc-utils libaio1
  libboost-iostreams1.62.0 libboost-random1.62.0 libboost-system1.62.0
  libboost-thread1.62.0 libklibc libnspr4 libnss3 librados2 libsgutils2-2
  liburcu4 sg3-utils sg3-utils-udev
Suggested packages:
  bash-completion multipath-tools-boot
Recommended packages:
  busybox | busybox-static
The following packages will be REMOVED:
  dracut* zfs-dracut*
The following NEW packages will be installed:
  initramfs-tools initramfs-tools-core klibc-utils libaio1
  libboost-iostreams1.62.0 libboost-random1.62.0 libboost-system1.62.0
  libboost-thread1.62.0 libklibc libnspr4 libnss3 librados2 libsgutils2-2
  liburcu4 multipath-tools sg3-utils sg3-utils-udev
0 upgraded, 17 newly installed, 2 to remove and 3 not upgraded.
[...]

I guess it's not the best idea to remove dracut from a FAI nfsroot.

> Do you need the multipath tools for booting the machine, or just for
> accessing some disk during installation?

To sort out 60 JBOD disks in a HGST box (very similar to Thumpers if you
still remember those) connected via two SAS cables. Both show up twice as
/dev/sd* and /dev/sg*, only once in /dev/disk/by-id, and twice in .../by-path
(obviously).

> If needed for booting, we may have to customized the initrd inside the
> nfsroot (copied to the tftp dir), because dracut may not work
> out-of-the-box with multipath devices.
> But I'm also the Debian maintainer of dracut, if you need some help.

Since dracut* is kind of an alternative approach to initramfs* you might want
to get your packages listed as alternatives, to resolve the dependencies, if
that's feasible (is it really a drop-in replacement?)
AFAICT it's sg3-utils-udev that causes the issue to show up, by depending
on initramfs-* stuff. With an udev involved, this looks a bit trickier than
with ordinary packages.

>     > Thanks for your constant support.
> It would be nice if you could update your FAI questionnaire. The last
> I got is from 2009. And I would like to add you to the references page
> with your logo. https://fai-project.org/references/

I'll try and do my best...


Cheers,
- S