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Grow a KVM virtual machine.adoc

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Assumption:

  • The virtual machine name is rhel7

  • The virtual machine is using qcow2 disk

  • The virtual machine disk path is /var/lib/libvirt/images/rhel7.qcow2

Resize the Virtual machine disk

  1. Stop the virtual machine

    virsh shutdown rhel7

  2. Create a new qcow2 image

    qemu-img create -f qcow2 -o preallocation=metadata /root/rhel7-new.qcow2 10G

  3. Resize the image

    virt-resize /var/lib/libvirt/images/rhel7.qcow2 /var/lib/libvirt/images/rhel7-new.qcow2

  4. Edit the virtual machine meta data pointing to the new image

    virsh edit rhel7

  5. Start the virtual Machine

    virsh start rhel7

  6. Find the IP address of the virtual machine

    # virsh domifaddr rhel7
 Name       MAC address          Protocol     Address
-------------------------------------------------------------------------------
vnet0      52:54:00:19:5b:9e    ipv4         192.168.122.23/24

Resize the LVM in the machine

  1. SSH into the virtual machine

    ssh root@<ip>

  2. Find out what the disk name is using fdisk

    fdisk -l

Disk /dev/vda: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0002ff53

   Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048     1026047      512000   83  Linux
/dev/vda2         1026048     4194303     1584128   8e  Linux LVM
/dev/vda3         4194304    20971455     8388576   83  Linux

Disk /dev/mapper/rhel-root: 9948 MB, 9948889088 bytes, 19431424 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/rhel-swap: 213 MB, 213909504 bytes, 417792 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

  3. Change system type for the new partition

    From the previous command we found out that the current disk is /dev/vda and that the new partition create by virt-resize is /dev/vda3. However the type of the new disk is Linux. To change the type we issue the following commands:

    # fdisk /dev/vda
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): t
Partition number (1-3, default 3): 3
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux LVM' to 'Linux LVM'

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

  4. Sync the disk using partprobe

    # partprobe

  5. Create Physical Volume

    # pvcreate /dev/vda3
  Physical volume "/dev/vda3" successfully created
    # pvdisplay
  --- Physical volume ---
  PV Name               /dev/vda2
  VG Name               rhel
  PV Size               1.51 GiB / not usable 3.00 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              386
  Free PE               11
  Allocated PE          375
  PV UUID               d9PV1O-XsrD-wSvM-OAhV-p9oY-ciXY-KBJs3t
    "/dev/vda3" is a new physical volume of "8.00 GiB"
--- NEW Physical volume ---
PV Name               /dev/vda3
VG Name
PV Size               8.00 GiB
Allocatable           NO
PE Size               0
Total PE              0
Free PE               0
Allocated PE          0
PV UUID               HXnFD0-ky0p-GByZ-Fm8k-UGQ6-hrMM-NPqyrh

  6. Add the new physical volume to the volume group

    # vgextend rhel /dev/vda3

  7. Extend the logica volume matching the size of the new physical volume

    # lvextend -L+8G /dev/rhel/root

  8. Resize the file system using either resize2fs for ext4 etc and xfs_growfs for xfs file system (default in RHEL 7)

    # xfs_growfs /dev/rhel/root

DONE