It is common for a virtualized Guest OS base image to have a generic storage capacity. This capacity can easily be exceeded by production scenarios, performance testing, logging, or even the general cruft of running a machine 24×7.
If your VM is using Logical Volume Management (LVM), adding space can be done by following a relatively simply recipe.
In this post, I will use the parted utility to create a new partition on an existing or new disk on an Ubuntu Focal guest OS. Then we will create a physical volume from this partition and associate it with the volume group. Finally, we extend the volume group and then have it recognized at the filesystem level.
For a visual representation of an LVM volume group, physical volumes, physical partitions, logical volumes, and filesystems the LVM wikipedia page has a nice graphic shown below.
Allocate additional storage
The first step is to either add a disk or extend the storage capacity of an existing disk for the specific virtualization backend being used.
This can be done with the virtualization engine’s preferred GUI or CLI tool. For example, using:
- KVM/QEMU
- add new disk, “virsh attach-disk”
- expand size of existing disk, “qemu-img resize”
- VirtualBox
- add new disk, vboxmanager storageattach
- expand size of existing disk, vboxmanage modifymedium
- vSphere, use the vSphere GUI client, PowerCLI, or other API tool
- vCloud Director you have this ability at the web client
Note that having snapshots on this VM may keep you from performing an extension of an existing disk.
Create the new physical partition
There are two ways you can add a new physical partition to extend the LVM volume group.
- Create a partition from space added to an existing disk
- Create a partition from a newly added disk
Important Note: Manipulating partitions can lead to a bricking of the virtualized guest OS. If you are not completely comfortable with this procedure in a development environment, do not even consider running it in production. Backup all critical data before executing this on a production system.
Option1: Create partition from newly added space on existing disk
If you added capacity to an existing disk, then you should be able to see it using the parted disk partition utility. In this example, we have added 11Gb to the existing “/dev/vda”.
# install parted sudo apt-get install parted -y # show list of available devices (e.g. /dev/vda) # but new partition is not shown yet because it is not defined lsblk
We now use parted to show us the partitions on /dev/vda.
# show partitions on /dev/vda in human readable form
# press "F" when asked to fix GPT to correct size
$ sudo parted -a optimal /dev/vda print free
Warning: Not all of the space available to /dev/vda appears to be used, you can fix the GPT to use all of the space (an extra 2097152 blocks) or continue with the current setting?
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 33.3GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
17.4kB 1049kB 1031kB Free Space
1 1049kB 2097kB 1049kB bios_grub
2 2097kB 1076MB 1074MB ext4
3 1076MB 21.5GB 20.4GB
21.5GB 33.3GB 11.8GB Free Space
The GPT size is now corrected, and we can see the free 11.8Gb of space available. But in order to create the partition we need to use the sector number so we change the units.
# show partition sector numbers
$ sudo parted -s -a optimal /dev/vda unit s print free
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 65011712s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
34s 2047s 2014s Free Space
1 2048s 4095s 2048s bios_grub
2 4096s 2101247s 2097152s ext4
3 2101248s 41940991s 39839744s
41940992s 65011678s 23070687s Free Space
From the output, we can see the free space has a starting sector at ‘41940992s’. We will use this information to create a partition now.
$ sudo parted -s -a optimal /dev/vda unit s \
mkpart primary 41940992s 100% \
set 1 lvm on \
align-check optimal 1 \
print free
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 65011712s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
34s 2047s 2014s Free Space
1 2048s 4095s 2048s lvm
2 4096s 2101247s 2097152s ext4
3 2101248s 41940991s 39839744s
4 41940992s 65009663s 23068672s primary
65009664s 65011678s 2015s Free Space
Now the space starting at 41940992s has been assigned to partition #4. There is a little bit of extra free space, but ignore that. That is purposeful leftover used to maintain healthy alignment.
A quick validation will show the extra capacity at /vda4. But creating this physical partition within an existing disk is just the prerequisite for adding it to the LVM volume group.
# should now show 11G at /vda4 lsblk
Option2: Create partition from new disk
If you created and attached a new disk, then you should be able to see it from a listing of the block devices. In this example, we have added a new 15Gb disk that shows up as “/dev/vdb”.
# install parted sudo apt-get install parted -y # show list of available devices (e.g. /dev/vdb) lsblk
We now use parted to create a new partition on /dev/vdb from the newly added space.
# create partition on /dev/vdb
$ sudo parted -a optimal /dev/vdb unit s \
mklabel gpt \
mkpart primary 2048s 100% \
align-check optimal 1 \
set 1 lvm on \
print free
odel: Virtio Block Device (virtblk)
Disk /dev/vdb: 31457280s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
34s 2047s 2014s Free Space
1 2048s 31455231s 31453184s primary lvm
31455232s 31457246s 2015s Free Space
We can see the free 15Gb (31453184 sectors) of space is available at partition #1. There is a little bit of extra free space on both ends, but ignore that. That is unnecessary leftover to maintain healthy alignment.
A quick validation will show the extra capacity at /dev/vdb1. But creating this physical partition on a new disk is just the prerequisite for adding it to the LVM volume group.
# should now show 15G at /dev/vdb1 lsblk
Create LVM PV from physical partition
Regardless of which path you took in the previous step; whether a physical partition was created on an extended existing disk (e.g. /dev/vda4) or a new disk (e.g. /dev/vdb1), you now have a physical partition.
Use ‘pvcreate’ so LVM recognizes this physical partition.
# use variable for the name of your physical partition # '/dev/vda4' or '/dev/vdb1' for this example export mypartition="/dev/vda4" # see list of current phys volumes known to LVM sudo pvs # create physical volume (force wipe) sudo -E pvcreate $mypartition -f # should now see new partition recognized sudo pvs
Associate physical partition to volume group
You need to associate the physical partition with the LVM volume group, which is done with ‘vgextend’.
# name of LVM volume groups
sudo vgs
# put name of LVM volume group into variable
export vgname=$(sudo vgs --noheading | awk '{print $1}')
echo "LVM vg name is $vgname"
# associate device to volume group
sudo -E vgextend $vgname $mypartition
# will now show relationship between partition and volume group
sudo pvs
Resize LVM volume group
Use ‘lvresize’ to have the LVM logical volume use the new physical partition.
# logical volume will still show old capacity
sudo lvs
# show logical volume full path (e.g. /dev/ubuntu-vg/ubuntu-lv)
sudo lvdisplay | grep "LV Path"
# put lv full path into variable
export lvfullpath=$(sudo lvdisplay -c | awk -F':' '{print $1}' | tr -d ' ')
echo "lv full path is $lvfullpath"
# have lv use all its available space
sudo -E lvresize -l +100%FREE $lvfullpath
# logical volume will now show new capacity
sudo lvs
Have filesystem recognize expanded space
While LVM now sees the additional space, the filesystem does not. For ext4 filesystems you can use resize2fs to have the space recognized.
# show space on LVM mount df -h # use to extend sudo -E resize2fs $lvfullpath # LVM mount now increased in size df -h
The new space is now reflected in the LVM mount and is available for use by the system.
REFERENCE
howtogeek.com, LVM cheat sheet
linux.die.net, parted man page
gnu.org, parted description of resizepart
tecmint.com, parted for creating rescue partitions
linoxide.com, parted for managing partitions
superuser.com, scripting parted
thegeekdiary.com, how to extend the fs partition with parted
rainbow.chard.org, how to align partitions
tylersguides.com, add disk to LVM, xfs_growfs
woshub.com, how to extend increase kvm disk, xfs_growfs/resize2fs
microhowto.info, how to increase LVM logical volume
computingforgeeks.com, extend kvm disk
slice2.com, resize default LVM on ubuntu 18
NOTES
alternative to lsblk to show devices
lshw -class disk -short
If using a non-LVM managed host, then you extend the ending sector of the existing partition on /dev/vda. Then resize2fs to have it recognized at filesystem level.
$ sudo parted /dev/vda
GNU Parted 3.3
Using /dev/vda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print free
Warning: Not all of the space available to /dev/vda appears to be used, you can fix the GPT to use all of the
space (an extra 20971520 blocks) or continue with the current setting?
Fix/Ignore? F
unit s
print free
odel: Virtio Block Device (virtblk)
Disk /dev/vda: 25583616s
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
34s 2047s 2014s Free Space
14 2048s 10239s 8192s bios_grub
15 10240s 227327s 217088s fat32 boot, esp
1 227328s 4612062s 4384735s ext4
4612063s 25583582s 20971520s Free Space
(parted) resizepart
Partition number? 1
Warning: Partition /dev/vda1 is being used. Are you sure you want to continue?
Yes/No? Y
End? [4612062s]? 25583582s
(parted) quit
# resize the filesystem
$ sudo resize2fs /dev/vda1
# verify disk change recognized
$ df -h