13.8. Converting a root filesystem to LVM 1

13.8.1. Boot single user

Boot into single user mode (type linux S at the LILO prompt) This is important. Booting single-user ensures that the root filesystem is mounted read-only and no programs are accessing the disk.

13.8.2. Run Parted

Run parted to shrink the root partition Do this so there is room on the disk for a complete copy of it in a logical volume. In this example a 1.8 gig partition is shrunk to 1 gigabyte This displays the sizes and names of the partitions on the disk

# parted /dev/hda (parted) p . . .

Now resize the partition:

(parted) resize 3 145 999

The first number here the partition number (hda3), the second is the same starting position that hda3 currently has. Do not change this. The last number should make the partition around half the size it currently is.

Create a new partition

(parted) mkpart primary ext2 1000 1999

This makes a new partition to hold the initial LVM 1 data. It should start just beyond the newly shrunk hda3 and finish at the end of the disk.

Quit parted

(parted) q

13.8.3. Reboot

Reboot the system

13.8.4. Verify kernel config options

Make sure that the kernel you are currently running works with LVM 1 and has CONFIG_BLK_DEV_RAM and CONFIG_BLK_DEV_INITRD set in the config file.

13.8.5. Adjust partition type

Change the partition type on the newly created partition from Linux to LVM (8e). Parted doesn't understand LVM 1 partitions so this has to be done using fdisk.

# fdisk /dev/hda Command (m for help): t Partition number (1-4): 4 Hex code (type L to list codes): 8e Changed system type of partition 4 to 8e (Unknown) Command (m for help): w

13.8.6. Set up LVM 1 for the new scheme

• Initialize LVM 1 (vgscan)

  # vgscan

• Make the new partition into a PV

  # pvcreate /dev/hda4

• create a new volume group

  # vgcreate vg /dev/hda4

• Create a logical volume to hold the new root.

  # lvcreate -L250M -n root vg

13.8.7. Create the Filesystem

Make a filesystem in the logical volume and copy the root files onto it.

# mke2fs /dev/vg/root # mount /dev/vg/root /mnt/ # find / -xdev | cpio -pvmd /mnt

13.8.8. Update /etc/fstab

Edit /mnt/etc/fstab on the new root so that / is mounted on /dev/vg/root. For example:

/dev/hda3 / ext2 defaults 1 1

becomes:

/dev/vg/root / ext2 defaults 1 1

13.8.9. Create an LVM 1 initial RAM disk

# lvmcreate_initrd
        

Make sure you note the name that lvmcreate_initrd calls the initrd image. It should be in /boot.

13.8.10. Update /etc/lilo.conf

Add an entry in /etc/lilo.conf for LVM 1. This should look similar to the following:

image = /boot/KERNEL_IMAGE_NAME label = lvm root = /dev/vg/root initrd = /boot/INITRD_IMAGE_NAME ramdisk = 8192

Where KERNEL_IMAGE_NAME is the name of your LVM 1 enabled kernel, and INITRD_IMAGE_NAME is the name of the initrd image created by lvmcreate_initrd. The ramdisk line may need to be increased if you have a large LVM 1 configuration, but 8192 should suffice for most users. The default ramdisk size is 4096. If in doubt check the output from the lvmcreate_initrd command, the line that says:

lvmcreate_initrd -- making loopback file (6189 kB)

and make the ramdisk the size given in brackets.

You should copy this new lilo.conf onto /etc in the new root fs as well.

# cp /etc/lilo.conf /mnt/etc/

13.8.11. Run LILO to write the new boot sector

# lilo
        

13.8.12. Reboot to lvm

Reboot - at the LILO prompt type "lvm" The system should reboot into Linux using the newly created Logical Volume.

If that worked then you should make lvm the default LILO boot destination by adding the line

default=lvm

in the first section of /etc/lilo.conf

If it did not work then reboot normally and try to diagnose the problem. It could be a typing error in lilo.conf or LVM 1 not being available in the initial RAM disk or its kernel. Examine the message produced at boot time carefully.

13.8.13. Add remainder of disk

Add the rest of the disk into LVM 1. When you are happy with this setup you can then add the old root partition to LVM 1 and spread out over the disk.

First set the partition type to 8e(LVM)

# fdisk /dev/hda Command (m for help): t Partition number (1-4): 3 Hex code (type L to list codes): 8e Changed system type of partition 3 to 8e (Unknown) Command (m for help): w

Convert it into a PV and add it to the volume group:

# pvcreate /dev/hda3 # vgextend vg /dev/hda3