Preseeding debian with software RAID (The kernel was unable to re-read the partition table … Invalid argument)


This is a problem I’ve been occasionally going back to for a couple months now. The problem is that I’m using preseed.cfg to perform a fully unattended debian installation via netboot and I keep hitting my head on this one obnoxious warning message “The kernel was unable to re-read the partition table on /dev/md2 (Invalid argument)”… which turns out doesn’t even matter. If you just hit “Ok” the installation goes through and succeeds just fine.

Today I spent hours researching preseed answers and all the processes and scripts involved in rendering these dialogs back to the user looking for any desperate means to abolish this message, when I got this other desperate idea…. cat /dev/mem > /mnt/mem . Yeah that’s right. I am going to personally read my RAM.

A quick search using less brought me to this section of the file:

@GO
T high partman/exception_handler_note
IPTION The kernel was unable to re-read the partition table on /dev/md2 (Invalid argument).  This means Linux won't know anything about the modifications you made until you reboot.  You should reboot your computer before doing anything w
ith /dev/md2.

And of course what stands out is high partman/exception_handler_note

A quick google search for “partman/exception_handler_note preseed.cfg” turns out a handful of samples where the line d-i partman/exception_handler_note note shows up in other folks’ configs. Why it was so difficult to track down this particular question for preseed is beyond me, but I suppose I’m just glad I didn’t give up on my roundabout detective work.

So the partition region of my preseed file looks like this:

d-i partman-auto/method string regular
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-md/device_remove_md boolean true
d-i partman-md/confirm boolean true

d-i partman-auto/disk string /dev/sdb
d-i partman-auto/method string raid

d-i partman-auto/expert_recipe string                   \
      multiraid ::                                      \
              500 1000000001 1000000000 raid                    \
                      $primary{ } method{ raid }                       \
              .                                         \
              512 513 512 raid                          \
                      $primary{ } method{ raid }        \
              .                                         \
              512 513 512 raid                          \
                      $primary{ } method{ raid }        \
              .

d-i partman-auto-raid/recipe string             \
    1 1 0 ext3 /                                \
          /dev/sdb1                             \
    .                                           \
    1 1 0 ext3 /mnt/utility                     \
          /dev/sdb2                             \
    .                                           \
    1 1 0 swap -                                \
          /dev/sdb3                             \
    .

d-i partman/exception_handler_note note
d-i partman-md/confirm boolean true
d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true

Beware…
Now of course I need to toss up some sort of disclaimer. The question “partman/exception_handler_note” is not very specific of course, and implies that this could be used for other unforeseeable problems. I’m comfortable using this because I’m in a controlled environment where I’m using the same distribution, installer version and same hardware across the board, but of course if you do this, you’re doing it at your own risk. I just have to say I’m so glad this is over.

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About andyortlieb

I often find myself figuring out some niche oddities, only to find myself stuck on those same problems a year later due to my wide yet thin activity in certain topics related to my career and hobbies. This blog is where I document these nuances (or nuisances) to ease my pain the second time around, and hopefully that of some other fellow desperate internet scouts.
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