I’m quite sure I’d resized qcow2 images before. However, when I needed to resize an image today for my VM at home, I totally forgot about it. Well, this means it’s a good excuse for me to just write down a few commands to help me in the future.
If you try to follow a long, two things you wanna keep in in mind: do it at your own risk, and always backup your data before you make change to it. Having said, that’s get started.
I have a qcow2 image originally allocated for 10GiB of space. It’s full, and I wanted to increase it to 20GiB.
/vm/rh415
➜ ls -lh workstation.qcow2
-rw-------. 1 root root 8.7G Dec 25 07:58 workstation.qcow2
To increase or expand the image size, we can run qemu-img resize IMAGE.qcow2 +SIZE command as the following:
➜ sudo qemu-img resize workstation.qcow2 +10G
[sudo] password for kenno:
Image resized.
➜ ls -lh workstation.qcow2
-rw-------. 1 root root 8.7G Dec 25 08:15 workstation.qcow2
In the above example, I intended to increase the workstation.qcow2 image file by 10GiB. Note that when we listed the file after resizing, it still displayed as 8.7GB. This is expected as qcow2 is a sparse file, it doesn’t pre-allocate the disk space until it’s used. You can read more about it here [1].
The next step is to resize this qcow2 image from the operating system. From here, the situations would be different depending on how the disk (qcow2 image) is configured and formatted with your system. I’m going to show you how to expand a disk configured as LVM on CentOS 7.
After booting the CentOS 7 VM, I can verify that the disk has been expanded to 21.5GB (I know, it isn’t exactly 20GiB I expected, but it doesn’t really matter.)
[root@workstation ~]# parted -s -a opt /dev/sda "print free"
Model: ATA QEMU HARDDISK (scsi)
Disk /dev/sda: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
32.3kB 1049kB 1016kB Free Space
1 1049kB 1075MB 1074MB primary xfs boot
2 1075MB 10.7GB 9663MB primary lvm
10.7GB 21.5GB 10.7GB Free Space
What does each option passed to parted do?
-s- execute this command as non-interactive script-a opt- use optimum alignment as given by the disk topology informationprint free- display the partition table including the free space
Before the LVM physical volume residing on partition 2 (/dev/sda2) can be expanded, I need to enlarge that partition to take up more space (10.7GB) first.
With the help from this link [2], I run the following command:
[root@workstation ~]# parted -s -a opt /dev/sda "resizepart 2 100%"
[root@workstation ~]# echo $?
0
[root@workstation ~]# parted -s -a opt /dev/sda "print free"
Model: ATA QEMU HARDDISK (scsi)
Disk /dev/sda: 21.5GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
32.3kB 1049kB 1016kB Free Space
1 1049kB 1075MB 1074MB primary xfs boot
2 1075MB 21.5GB 20.4GB primary lvm
A brief explanation of the above command, basically I wanted to resize partition 2 to use all the available free space. The echo $? is optional, it’s just to show that the previous command was executed successfully. The last command in the above output was just to confirm that the size of partition 2 has been increased.
[root@workstation ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name cl
PV Size <9.00 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2303
Free PE 0
Allocated PE 2303
PV UUID N6ROGe-H1y3-f62b-yraO-yDxL-I5lH-66WDUd
Next, I need to expand the physical disk of the LVM. In my case, the partition that I wanted to resize is /dev/sda2.
[root@workstation ~]# pvresize /dev/sda2
Physical volume "/dev/sda2" changed
1 physical volume(s) resized or updated / 0 physical volume(s) not resized
[root@workstation ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name cl
PV Size <19.00 GiB / not usable 2.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 4863
Free PE 2560
Allocated PE 2303
PV UUID N6ROGe-H1y3-f62b-yraO-yDxL-I5lH-66WDUd
So far so good. There are some free PE (physical extend) of 2560. I can use it to expand other LVM. For example, I’m going to allocate an additional 5GiB to the root logical volume.
[root@workstation ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root cl -wi-ao---- <8.00g
swap cl -wi-ao---- 1.00g
[root@workstation ~]# lvresize -L +5GiB /dev/cl/root
Size of logical volume cl/root changed from <8.00 GiB (2047 extents) to <13.00 GiB (3327 extents).
Logical volume cl/root successfully resized.
[root@workstation ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root cl -wi-ao---- <13.00g
swap cl -wi-ao---- 1.00g
References:
The last step is to resize the actual filesystem used by the root logical volume.
[root@workstation ~]# lsblk -fs | grep root
cl-root xfs cccaadf6-4748-4b8b-98dc-eb205c785bb5 /
[root@workstation ~]# xfs_growfs /dev/mapper/cl-root
meta-data=/dev/mapper/cl-root isize=512 agcount=4, agsize=524032 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=2096128, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 2096128 to 3406848
[root@workstation ~]# df -lh | grep root
/dev/mapper/cl-root 13G 7.9G 5.2G 61% /
Well, that’s it folks.