I’ve been meaning to post my notes on this for a while but I wanted to post some code which needs to be stripped of the proprietary work. At my job, we have a need to do multiple installs a day of ubuntu via the network and require a fairly complex lvm configuration. When done on feisty, first you need to deal with the three minutes it takes to create the lvm devices. This is a bug, check out this post about it.

Partman-auto and partman-lvm-auto configuration recipes are pretty complex to begin with. If you’re not simply formatting the whole disk, it can get really confusing, let alone figuring out the difference between partman and partman-lvm. There’s some sample code out there, but it’s hard to tell when era it’s from. Upon learning that partman-auto wasn’t going to support multiple disks, I started looking for alternatives. Thanks to cjwatson and fjp for pointing me in the right directions at times.

Finding the right hooks was the hard part. debian-installer (or d-i) is the alternative and network (pxe based) installer for ubuntu. It’s very modular and uses anna (the lightweight version of apt) specific udeb (anna’s version of debs) configurations to let d-i know in what order a specific module should be run. Basically what I did was force partman not to run, and have a shell script run instead.

Assuming that you’ve already got a pxe install going with a preseed file, use the following:

d-i preseed/early_command string wget http://server.example.com/ubuntu/config/lvm.sh -P /tmp ; chmod 755 /tmp/lvm.sh ; echo /tmp/lvm.sh installer >> /var/lib/dpkg/info/download-installer.postinst

This will download your script and set it to be executed after the base installer is downloaded. This is important because some of the install system is in the initrd, but a lot of it, partman included, is installed from a udeb after the initrd is loaded. So you can’t just hack partman from inside the initrd.

lvm.sh is a two phase script. the first is run when the base installer is setup, by the earlier call in download-installer.postinst. This phase then sets itself to be run instead of partman, allowing you to create and mount your partitions at the correct time.

Note that you should have your disk mounted as /target by the end of phase 2 as well as have your fstab configured. I’d also recommend running swapon against your swap, but keep in mind that the mkswap currently shipping will only prepare 2GB of swapspace, see bug 119900.

Theres some extra stuff in this script you won’t need. It’s also untested with my companies stuff removed. If having a bunch of lvms named ‘stuffN’ seems stupid, it’s because that’s my way of obfuscating the code so I won’t have someone from work complain. As always, YMMV.

#!/bin/sh
# Manually create LVM configuration
# Partman does not currently support multi-disk lvm
# Designed to be run after download-installer but before partman-base
# This allows us to modify partman-base.postinst after it's been dropped in by anna
# Partman appears to be entirely an external program, removing the call to partman from partman-base.postinst prevents it from running.

case "$1" in
 installer)
  # we should have d-i downloaded by now.
  # partman comes in a udeb from the network so we have to hook here
  # and replace the partman-base.postinst file
  sed -i 's/partman/\/tmp\/lvm.sh partman/' /var/lib/dpkg/info/partman-base.postinst
  logger lvm.sh modified partman-base.postinst
 ;;
 partman)
  # do filesystem stuff: detect our config, fdisk, lvms, mount /target
  logger lvm.sh partition configuration starting
  modprobe dm_mod

  # FIXME: This is going to be really dirty to handle our configurations. More work will need to be done later.
  #      case1: sda: 1171842048 hda: 125056
  #      case2: sda: 976519168 hda: 58605120
  #      case3: sda: 732389376 hda:
  
  SIZE_SDA=`sed -n 's/.* \([0-9]*\) sda$/\1/p' < /proc/partitions`
  SIZE_HDA=`sed -n 's/.* \([0-9]*\) hda$/\1/p' < /proc/partitions`

  echo sda: $SIZE_SDA hda: $SIZE_HDA
  
  # pvcreate filters (ignored by filtering) if the there's a partition table
  dd if=/dev/zero of=/dev/sda bs=512 count=1
 
  # check for separate physical boot drive
  if [ $SIZE_HDA ] ; then
   # we have the boot disk create a primary partition
   echo ",,83" | sfdisk /dev/hda
  
   
   pvcreate -ff -y /dev/sda
   BOOT=/dev/hda1
   LVM=/dev/sda
  else
   # no separate boot drive
   echo -e ",256,83\n,,8e" | sfdisk -uM /dev/sda

   pvcreate -ff -y /dev/sda2
   BOOT=/dev/sda1
   LVM=/dev/sda2
  fi
  
  mke2fs -q $BOOT
  vgcreate -s 256M system $LVM
  
  if [ $SIZE_SDA -gt 700000000 ] ; then
   COMPLEXFS=1
   lvcreate -L 20G -n stuff1 system
   lvcreate -L 20G -n stuff2 system
   lvcreate -L 8G -n swap system
   lvcreate -L 20G -n stuff3 system
   lvcreate -L 200G -n stuff4 system
   lvcreate -L 200G -n stuff5 system
   lvcreate -L 200G -n stuff6 system

   for fs in stuff1 stuff2 stuff3 stuff4 stuff5 stuff6 ; do mkfs.reiserfs -q /dev/system/$fs 1>/dev/null; done

  else
   # FIXME: swap too big for vmware
   lvcreate -L 8G -n swap system
   lvcreate -l `pvdisplay | sed -n 's/Free PE \([0-9]*\)/\1/p'` -n config1 system

   mkfs.reiserfs -q /dev/system/stuff1 1>/dev/null
  fi

  # setup common swap
  mkswap /dev/system/swap
  swapon /dev/system/swap

  # Create directory structure
  mkdir /target
  mount /dev/system/stuff11 /target -treiserfs
  mkdir /target/boot
  mount $BOOT /target/boot -text2
  if [ $COMPLEXFS ] ; then
   mkdir -p /target/stuff2
   mkdir -p /target/stuff3
   mkdir -p /target/stuff4
   mount /dev/system/stuff2 /target/stuff2
  fi

  # Create fstab 
  mkdir /target/etc
  echo \# /etc/fstab: static file system information. > /target/etc/fstab
  echo \# >> /target/etc/fstab
  echo "#                   " >> /target/etc/fstab
  echo $BOOT     /boot   ext2  defaults  1  2 >> /target/etc/fstab
  echo /dev/system/stuff1       /    reiserfs acl,user_xattr 1  1 >> /target/etc/fstab
  if [ $COMPLEXFS ] ; then
   echo /dev/system/stuff2  /stuff2   reiserfs acl,user_xattr 1  2 >> /target/etc/fstab
   echo /dev/system/stuff3  /stuff3  reiserfs acl,user_xattr 1  2 >> /target/etc/fstab
   echo /dev/system/stuff4  /stuff4  reiserfs acl,user_xattr 1  2 >> /target/etc/fstab
  fi  
  echo /dev/system/swap  none   swap  sw    0  0 >> /target/etc/fstab
  echo proc     /proc   proc     defaults        0       0 >> /target/etc/fstab

  # Secret udev rules hack for network cards
  mkdir -p /target/etc/udev/rules.d
  echo \# on board e100 > /target/etc/udev/rules.d/50-network.rules
  echo KERNELS==\"0000:00:06.0\", NAME=\"eth2\" >> /target/etc/udev/rules.d/50-network.rules
  echo \# on board tg3 \(2x1000\) >> /target/etc/udev/rules.d/50-network.rules
  echo KERNELS==\"0000:02:09.0\", NAME=\"eth0\" >> /target/etc/udev/rules.d/50-network.rules
  echo KERNELS==\"0000:02:09.1\", NAME=\"eth1\" >> /target/etc/udev/rules.d/50-network.rules

 ;;
 *)
  echo $0: This script is destructive and should only be run as part of the debian-installer process
 ;;
esac