complex lvm on an alternative install of ubuntu (debian-installer)

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