Laurențiu Păncescu
Resizing the disk of a Vagrant guest
Some people occasionally ask in #centos how to resize the disk of a virtual machine. Most Linux distributions use LVM by default, which simplifies things considerably:
- Resize the disk image using the native tools provided by your virtualization software;
- Add a new partion inside the guest and use it for a new LVM physical volume;
- Extend the existing volume group to include the new physical volume;
- Extend the logical volume whose size you’d like to increase and resize its filesystem accordingly.
As an example, we’ll resize the disk of a Vagrant guest using
centos/7, the official CentOS Linux 7 image for Vagrant.
Resizing the disk image
Vagrant boxes use disk image in VMware’s VMDK format (simply because
they are cloned from an exported OVA file). VMware’s vdiskmanager
tool can resize such images directly, but VirtualBox and QEMU don’t
support resizing VMDKs natively, so we have to convert the disk image
to another format, and then convert it back after resizing. Of
course, the guest needs to be powered off before resizing its disk
image.
VirtualBox can only resize disk images in its native VDI format:
VBoxManage clonemedium disk centos-7-1-1.x86_64.vmdk centos-7-1-1.x86_64.vdi --format vdi
VBoxManage modifymedium disk centos-7-1-1.x86_64.vdi --resize 65536
VBoxManage clonemedium disk centos-7-1-1.x86_64.vdi centos-7-1-1.x86_64.vmdk --existing
With QEMU, we have to convert the image to the “raw” file format,
increase its size with dd and then convert it back to the VMDK
format:
qemu-img convert -O raw centos-7-1-1.x86_64.vmdk tmp.raw
dd if=tmp.raw of=centos-7-1-1.x86_64.raw bs=1M seek=65536 oflag=append
qemu-img convert -O vmdk centos-7-1-1.x86_64.raw centos-7-1-1.x86_64.vmdk
Resizing the guest filesystem
The new disk size is seen correctly by the guest, after booting it again:
$ sudo parted /dev/sda
GNU Parted 3.1
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) print free
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 68.7GB
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 2097kB 1049kB primary
2 2097kB 1076MB 1074MB primary xfs boot
3 1076MB 42.9GB 41.9GB primary lvm
42.9GB 68.7GB 25.8GB Free Space
We can now create a new primary partition covering the free space and mark it for use with LVM:
(parted) mkpart primary 42.9G 100%
(parted) set 4 lvm on
(parted) quit
Information: You may need to update /etc/fstab.
No changes to /etc/fstab are necessary in our case (the new
partition will only be used by LVM inside the logical volume for
root, it will never be mounted directly).
We can now create a new LVM physical volume in the partition we just created and extend the existing volume group:
$ sudo pvcreate /dev/sda4
Physical volume "/dev/sda4" successfully created.
$ sudo pvs
PV VG Fmt Attr PSize PFree
/dev/sda3 VolGroup00 lvm2 a-- 38.97g 0
/dev/sda4 lvm2 --- 24.00g 24.00g
$ sudo vgextend VolGroup00 /dev/sda4
Volume group "VolGroup00" successfully extended
The last step is to resize the LVM logical volume for root and the filesystem it hosts:
$ sudo lvextend /dev/mapper/VolGroup00-LogVol00 -rl +100%FREE
Size of logical volume VolGroup00/LogVol00 changed from 37.47 GiB (1199 extents) to 61.44 GiB (1966 extents).
Logical volume VolGroup00/LogVol00 successfully resized.
meta-data=/dev/mapper/VolGroup00-LogVol00 isize=512 agcount=4, agsize=2455552 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=9822208, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=4796, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 9822208 to 16105472