Migrating a Linux boot partition to RAID-1

Alexander Hajnal

3 Preparation

3.1 You will need a new disk that is at least a large as your current boot disk. Ideally, this drive would be the same model and capacity as your existing drive. We will refer to this disk as the new disk.
3.2 You have a backup copy of all of the data on your current boot disk. You can do this by using either dd or cp:
- dd if=/dev/hda of=/dev/hdd where /dev/hdd is a blank disk of equal or larger size. This will overwrite any data already on /dev/hdd
  or
- cp -ax / /path/to/backup/directory
3.3 Compile a kernel with native RAID-1 support:
- 3.3.1 cd /usr/src/linux
- 3.3.2 make menuconfig or make xconfig
- 3.3.3 Select the following options:
  - Multi-device support (RAID and LVM)
    - Multi-device support (RAID and LVM) → select y
    - RAID support → select y
    - RAID-1 (mirroring) mode → select y
  Make sure that you select y and not m for these options; if you select m (for modules), you will not be able to boot off of the RAID array.
- 3.3.4 The following option should be set to n:
  - ATA/IDE/MFM/RLL support
    - IDE, ATA and ATAPI Block devices
      
      Support for IDE Raid controllers (EXPERIMENTAL) → n
If you choose to use a pre-compiled kernel (with native RAID-1 built-in) that has been supplied by your vendor, you should install it now and skip the above steps on building and installing a kernel from source.

Install the raidtools2 package.
On Debian systems you can do this with apt-get install raidtools2 If you are using a different distribution, install the package using your normal package installation tool. On Debian, you will be asked whether you want to start all RAID arrays described in /etc/raidtab at system startup. Say yes to this. Note that for the array to bootable, you will still need to add it to /etc/lilo.conf. This is explained later in this document.
The raidtools2 package contains the following tools:

arytst   detect_multipath   lsraid   mkraid

raid0run   raidhotadd   raidhotgenerateerror   raidhotremove

raidreconf   raidsetfaulty   raidstart   raidstop

Find the label of the default kernel in /etc/lilo.conf and write down its value (look for a line that starts with default=). In this example, we will assume that the label is linux

Find the boot device in /etc/lilo.conf and write down its location (look for a line that starts with boot=). In this example, we will assume that it is /dev/hda

Find your root partition /etc/lilo.conf and write down its location (look for a line that starts with root=). In this example, we will assume that it is /dev/hda1

`arytst`	`detect_multipath`	`lsraid`	`mkraid`
`raid0run`	`raidhotadd`	`raidhotgenerateerror`	`raidhotremove`
`raidreconf`	`raidsetfaulty`	`raidstart`	`raidstop`