Logical Volume Management (LVM) is a disk management option that every
major Linux distribution includes. Whether you need to set up storage
pools or just need to dynamically create partitions, LVM is probably
what you are looking for.
With LVM, disks and partitions can be abstracted to contain multiple disks and partitions into one device. Your operating systems will never know the difference because LVM will only show the OS the volume groups (disks) and logical volumes (partitions) that you have set up.
Because volume groups and logical volumes aren’t physically tied to a hard drive, it makes it easy to dynamically resize and create new disks and partitions. In addition, LVM can give you features that your file system is not capable of doing. For example, Ext3 does not have support for live snapshots, but if you’re using LVM you have the ability to take a snapshot of your logical volumes without unmounting the disk.
If you are using Ubuntu on a laptop with only one internal hard drive and you don’t need extended features like live snapshots, then you may not need LVM. If you need easy expansion or want to combine multiple hard drives into a single pool of storage then LVM may be what you have been looking for.
To install Ubuntu using LVM you need to use the alternate install CD. Download it from the link below and burn a CD or use unetbootin to create a USB drive.
Boot your computer from the alternate install disk and select your options up until the partition disks screen and select guided – use entire disk and set up LVM.
Note: This will format your entire hard drive so if you are trying to dual boot or have another installation select manual instead.
Select the main disk you want to use, typically your largest drive, and then go to the next step.
You will immediately need to write the changes to disk so make sure you selected the right disk and then write the changes.
Select the size you want the first logical volume to be and then continue.
Confirm your disk partitions and continue with the installation.
The final step will write the GRUB bootloader to the hard drive. It is important to note that GRUB cannot be on an LVM partition because computer BIOSes cannot directly read from a logical volume. Ubuntu will automatically create a 255 MB ext2 partition for your bootloader.
After the installation is complete, reboot the machine and boot into Ubuntu as normal. There should be no perceivable difference between using LVM or traditional disk management with this type of installation.
To use LVM to its full potential, stay tuned for our upcoming article on managing your LVM installation.
Download Ubuntu alternate CD
from https://www.howtogeek.com/howto/36568/what-is-logical-volume-management-and-how-do-you-enable-it-in-ubuntu/
http://www.howtogeek.com/howto/40702/
----------------
What is LVM?
Logical Volume Manager allows for a layer of abstraction between your operating system and the disks/partitions it uses. In traditional disk management your operating system looks for what disks are available (/dev/sda, /dev/sdb, etc.) and then looks at what partitions are available on those disks (/dev/sda1, /dev/sda2, etc.).With LVM, disks and partitions can be abstracted to contain multiple disks and partitions into one device. Your operating systems will never know the difference because LVM will only show the OS the volume groups (disks) and logical volumes (partitions) that you have set up.
Because volume groups and logical volumes aren’t physically tied to a hard drive, it makes it easy to dynamically resize and create new disks and partitions. In addition, LVM can give you features that your file system is not capable of doing. For example, Ext3 does not have support for live snapshots, but if you’re using LVM you have the ability to take a snapshot of your logical volumes without unmounting the disk.
When Should You Use LVM?
The first thing your should consider before setting up LVM is what you want to accomplish with your disks and partitions. Some distributions, like Fedora, install with LVM by default.If you are using Ubuntu on a laptop with only one internal hard drive and you don’t need extended features like live snapshots, then you may not need LVM. If you need easy expansion or want to combine multiple hard drives into a single pool of storage then LVM may be what you have been looking for.
Setting up LVM in Ubuntu
First thing to know about using LVM is there is no easy way to convert your existing traditional partitions to logical volumes. It is possible to move to a new partition that uses LVM, but that won’t be something that we will cover in this article; instead we are going to take the approach of setting up LVM on a fresh installation of Ubuntu 10.10.To install Ubuntu using LVM you need to use the alternate install CD. Download it from the link below and burn a CD or use unetbootin to create a USB drive.
Boot your computer from the alternate install disk and select your options up until the partition disks screen and select guided – use entire disk and set up LVM.
Note: This will format your entire hard drive so if you are trying to dual boot or have another installation select manual instead.
Select the main disk you want to use, typically your largest drive, and then go to the next step.
You will immediately need to write the changes to disk so make sure you selected the right disk and then write the changes.
Select the size you want the first logical volume to be and then continue.
Confirm your disk partitions and continue with the installation.
The final step will write the GRUB bootloader to the hard drive. It is important to note that GRUB cannot be on an LVM partition because computer BIOSes cannot directly read from a logical volume. Ubuntu will automatically create a 255 MB ext2 partition for your bootloader.
After the installation is complete, reboot the machine and boot into Ubuntu as normal. There should be no perceivable difference between using LVM or traditional disk management with this type of installation.
To use LVM to its full potential, stay tuned for our upcoming article on managing your LVM installation.
Download Ubuntu alternate CD
from https://www.howtogeek.com/howto/36568/what-is-logical-volume-management-and-how-do-you-enable-it-in-ubuntu/
http://www.howtogeek.com/howto/40702/
----------------
Mounting LVM Disk using Ubuntu livecd
Mounting is an easy process to do, provided the filesystem type you
are using is supported. What happen when you have an LVM formatted disk,
and you need to mount it because the disk cannot be booted and a hell
lot of valuable data kept inside?? Do not worry, because the solution is
here.......
1. Get a live cd, for example, Ubuntu. For this article, I use Ubuntu 6.06 (I cannot find any latest version of ubuntu at my place)
2. Boot using the live cd. Search for these tools: lvm2. If the cd do not have it, install it.
# apt-get install lvm2
3. To make sure the harddisk is recognised, you can use fdisk
# fdisk -lu
4. Once installed, run pvscan to scan all disks for physical volume. this to make sure your LVM harddisk is detected by Ubuntu
# pvscan
PV /dev/sda2 VG VolGroup00 lvm2 [74.41 GB / 32.00 MB free]
Total: 1 [74.41 GB] / in use: 1 [74.41 GB] / in no VG: 0 [0 ]
5. After that run vgscan to scan disks for volume groups.
# vgscan
Reading all physical volumes. This may take a while...
Found volume group "VolGroup00" using metadata type lvm2
6. Activate all volume groups available.
# vgchange -a y
2 logical volume(s) in volume group "VolGroup00" now active
7. Run lvscan to scan all disks for logical volume. You can see partitions inside the hard disk now active.
# lvscan
ACTIVE '/dev/VolGroup00/LogVol00' [72.44 GB] inherit
ACTIVE '/dev/VolGroup00/LogVol01' [1.94 GB] inherit
8. Mount the partition to any directory you want, usually to /mnt
# mount /dev/VolGroup00/LogVol00 /mnt
9. You can access the partition in the /mnt directory and can backup your data
1. Get a live cd, for example, Ubuntu. For this article, I use Ubuntu 6.06 (I cannot find any latest version of ubuntu at my place)
2. Boot using the live cd. Search for these tools: lvm2. If the cd do not have it, install it.
# apt-get install lvm2
3. To make sure the harddisk is recognised, you can use fdisk
# fdisk -lu
4. Once installed, run pvscan to scan all disks for physical volume. this to make sure your LVM harddisk is detected by Ubuntu
# pvscan
PV /dev/sda2 VG VolGroup00 lvm2 [74.41 GB / 32.00 MB free]
Total: 1 [74.41 GB] / in use: 1 [74.41 GB] / in no VG: 0 [0 ]
5. After that run vgscan to scan disks for volume groups.
# vgscan
Reading all physical volumes. This may take a while...
Found volume group "VolGroup00" using metadata type lvm2
6. Activate all volume groups available.
# vgchange -a y
2 logical volume(s) in volume group "VolGroup00" now active
7. Run lvscan to scan all disks for logical volume. You can see partitions inside the hard disk now active.
# lvscan
ACTIVE '/dev/VolGroup00/LogVol00' [72.44 GB] inherit
ACTIVE '/dev/VolGroup00/LogVol01' [1.94 GB] inherit
8. Mount the partition to any directory you want, usually to /mnt
# mount /dev/VolGroup00/LogVol00 /mnt
9. You can access the partition in the /mnt directory and can backup your data
- $ modprobe dm-mod
Otherwise you get the following:
$ lvscan
/proc/misc: No entry for device-mapper found
Is device-mapper driver missing from kernel?
-
Anonymous said...
-
Thanks a lot, for the post and anonymous for the comment about modprobe dm-mod!
At first, I got a couple of lines like:
ubuntu@ubuntu:~$ sudo vgchange -a y
/proc/misc: No entry for device-mapper found
Is device-mapper driver missing from kernel?
Failure to communicate with kernel device-mapper driver.
and lvscan gave problems as well:
Failure to communicate with kernel device-mapper driver.
Incompatible libdevmapper 1.02.20 (2007-06-15)(compat) and kernel driver
inactive '/dev/tmp/tmp' [2.00 GB] inherit
After sudo modprobe dm-mod, it worked like a charm.
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