- 1 Adding a new disk (LVM) to a VMware Workstation Ubuntu VM
- 2 Removing a disk from LVM on an Ubuntu system
- 2.1 Make a backup
- 2.2 Distributing Old Extents to Existing Disks in Volume Group
- 2.3 Remove the unused disk
- 2.4 References
Adding a new disk (LVM) to a VMware Workstation Ubuntu VM
For all steps listed, I’m working with an Ubuntu 10.04 LTS virtual machine. It consists of a single disk (/dev/sda) that I didn't size properly when I originally created the VM.
Later I added a second disk (/dev/sdb, independent of snapshots) to hold audio files from ripping cds prior to transferring to them to a player. I did not add this disk to the existing logical volume.
Now we’re going add a third disk (/dev/sdc) to the VM and place it in the same volume group as the original disk to help alleviate the space problem as shown here:
Filesystem Size Used Avail Use% Mounted on /dev/mapper/ubuntu-root 7.3G 6.5G 487M 94% / none 245M 264K 244M 1% /dev none 249M 1.1M 248M 1% /dev/shm none 249M 92K 249M 1% /var/run none 249M 0 249M 0% /var/lock none 249M 0 249M 0% /lib/init/rw /dev/sda1 236M 54M 170M 24% /boot /dev/sdb1 30G 497M 30G 2% /media/bucket .host:/ 79G 68G 12G 86% /mnt/hgfs
Adding the new disk
Go about adding the virtual disk through the method you're familiar with, keeping in mind that it will be combined with the existing LVM group already in place.
Creating the physical volume
I've found that you don't have to partition the disk prior to running this command.
Physical volume "/dev/sdc" successfully created
Listing the existing volume groups
--- Volume group --- VG Name ubuntu System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 3 VG Access read/write VG Status resizable MAX LV 0 Cur LV 2 Open LV 2 Max PV 0 Cur PV 1 Act PV 1 VG Size 7.76 GiB PE Size 4.00 MiB Total PE 1986 Alloc PE / Size 1986 / 7.76 GiB Free PE / Size 0 / 0 VG UUID t8CdgQ-IyfB-SqI5-C9Jc-M6w2-oNhe-1UuNZy
Extending the existing volume group
The ubuntu volume group was found, so let's add to that one.
vgextend ubuntu /dev/sdc
Volume group "ubuntu" successfully extended
Using the new disk
The logical volume manager doesn’t know anything about the contents of its volumes, so you must do your resizing at both the volume and filesystem levels. The order depends on the specific operation. Reductions must be filesystem-first, and enlargements must be volume-first. Don’t memorize these rules: just think about what’s actually happening and use common sense.
Resizing the logical volume
We added a 20 GB virtual disk and added the space to the volume group with the last command, but we haven't resized the logical volume (think of it as a container for a partition) to use any of the new space.
I've tried specifying the space I wanted to extend the logical volume in megabtyes, but I prefer specifying it via logical extents (the units of space allocation within a volume group) instead. I find this easier for some reason.
To do that, we need to get the number of logical extents available. We'll use
vgdisplay for this.
--- Volume group --- VG Name ubuntu System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 4 VG Access read/write VG Status resizable MAX LV 0 Cur LV 2 Open LV 2 Max PV 0 Cur PV 2 Act PV 2 VG Size 27.75 GiB PE Size 4.00 MiB Total PE 7105 Alloc PE / Size 1986 / 7.76 GiB Free PE / Size 5119 / 20.00 GiB VG UUID t8CdgQ-IyfB-SqI5-C9Jc-M6w2-oNhe-1UuNZy
What we're looking for is prefaced with Free PE / Size and and in this case it's 5119. So, that's one piece of information we need. Now, we need to know which logical volume we're resizing and we can get that information by using
lvdisplay to show the logical volume names:
lvdisplay | grep 'LV Name'
LV Name /dev/ubuntu/root LV Name /dev/ubuntu/swap_1
Well, we don't want to resize the swap_1 logical volume, so it's safe to say we want to resize ubuntu/root.
lvresize -l +5119 ubuntu/root
Extending logical volume root to 27.37 GiB Logical volume root successfully resized
Resizing the file system
Now that the container has grown large enough to hold a bigger file system, we resize the file system to fill it.
resize2fs 1.41.11 (14-Mar-2010) Filesystem at /dev/ubuntu/root is mounted on /; on-line resizing required old desc_blocks = 1, new_desc_blocks = 2 Performing an on-line resize of /dev/ubuntu/root to 7175168 (4k) blocks. The filesystem on /dev/ubuntu/root is now 7175168 blocks long.
Here's our file system/disk space usage:
root@ubuntu:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/ubuntu-root 27G 6.5G 20G 26% / none 245M 264K 244M 1% /dev none 249M 156K 249M 1% /dev/shm none 249M 88K 249M 1% /var/run none 249M 0 249M 0% /var/lock none 249M 0 249M 0% /lib/init/rw /dev/sda1 236M 54M 170M 24% /boot /dev/sdb1 30G 497M 30G 2% /media/bucket .host:/ 79G 68G 12G 86% /mnt/hgfs
References (in the order I used them)
- Unix and Linux System Administration Handbook, 4th Edition
- Suji's blog - How to add a disk to LVM
- howtoforge.com - A Beginner's Guide To LVM
- howtogeek.com - How to Manage and Use LVM (Logical Volume Management) in Ubuntu
Removing a disk from LVM on an Ubuntu system
This section pulls heavily from The Linux Documentation Project's "LVM HOWTO" . It also assumes that the disk you want to remove is
/dev/sdc. Substitute the device you wish to remove accordingly.
Make a backup
You've been warned.
Distributing Old Extents to Existing Disks in Volume Group
To do this, you'll need to have enough free extents on the other disks in the volume group.
You do not have enough free extents on the other disks in the volume group
Like myself, you probably assigned 100% of the free extents on this disk and all other disks in the volume group, so you'll need to free some up to hold any data displaced by removing
/dev/sdc from the system. 
Resize file system and logical volume via a Rescue Disc
In my case I'm using Ubuntu 10.04.x Server LTS, so I used that install disc. If you have a desktop environment, use the desktop install cd. From the boot menu, choose
Try Ubuntu without any change to your computer .
- I inserted the installation iso in the drive (or virtual cdrom) and booted from it.
- If you used the desktop install disc, you'll need to run
sudo -sto gain root privileges and then
apt-get install lvm2to gain access to the
lvm2package and related utilities.
- If you use the server install disc, chose not to mount a file system (since we're going to be resizing the root file system). The rest of the directions should work for the server or desktop install disc.
- Once at the root shell (busybox), enter
vgchange -a y
2 logical volume(s) in volume group "ubuntu" now active
resize2fs /dev/ubuntu/root -M
Please run 'e2fsck -f /dev/ubuntu/root' first
e2fsck -f /dev/ubuntu/root
- Once the disk passes the
resize2fs /dev/ubuntu/root -M. This may take a while. 
Now that the file system has been shrunk, let's resize the logical volume using the
lvresize. Before doing that, we'll want to verify the extents used by the disk we want to remove and then shrink the logical volume by that many extents.
pvdislay /dev/sdc | grep 'Total PE'
Total PE 5119
lvresize -l -5119 ubuntu/root
- Accept any warnings and continue, because after all, you did do a backup first (right?).
e2fsck -f /dev/ubuntu/root
resize2fs /dev/ubuntu/root(run without a size option so it will expand to the size it was before adding
pvmove ubuntu /dev/sdc
No extents available for allocation
- That probably shouldn't be ignored, but I went ahead and ran
vgreduce ubuntu /dev/sdcand got
Removed "/dev/sdc" from volume group "ubuntu"
- Reboot back into the main OS to see if it imploded (it did).
- Cover adding a temporary disk to LVM to hold content from /dev/sdc
- Possibly uninstalling a bunch of stuff from /dev/ubuntu/root so it will contain enough free space once /dev/sdc is removed (not using the temp disk approach).
I skipped a step somewhere and will need to go back and fix the directions here
You have enough free extents on the other disks in the volume group
If you choose to have your root file system in one logical volume and the extra disk placed in another logical volume, you can follow the directions below to resize the logical volume and filesystem so you can safely remove the disk.
pvmove -- moving physical extents in active volume group "ubuntu" pvmove -- WARNING: moving of active logical volumes may cause data loss! pvmove -- do you want to continue? [y/n] y pvmove -- 5119 extents of physical volume "/dev/sdc" successfully moved
Remove the unused disk
vgreduce ubuntu /dev/sdc
vgreduce -- doing automatic backup of volume group "ubuntu" vgreduce -- volume group "ubuntu" successfully reduced by physical volume: vgreduce -- /dev/sdc
- LVM-HOWTO - Removing an Old Disk
- Shrinking and growing a logical volume in Fedora 15
- This is probably not the most efficient way to handle it, but it should work fine, even if it takes longer than it would if we used (NEW_SIZE = CURRENT_SIZE - DISK_TO_REMOVE_SIZE)