Warning — These pages discuss older technologies. Though the high-level concepts are still valid, some of the low-level specifics (Linux 2.4, LILO, IDE disks, etc.) are obsolete. You probably don't want to go through these steps verbatim on a modern system.

Migrating a Linux boot partition to RAID-1

• 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
  • 3.3.5  Save your new kernel configuration and exit the configuration program.
  • 3.3.6  Build and install the new kernel by running:
    make dep && make && make modules && make modules_install && make install
    When prompted, say y to have lilo install the new kernel.
  • 3.3.7  Assuming that the kernel built and installed cleanly, you should now reboot the machine to make sure that the new kernel is working correctly.
  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