{{tag>[kvm lvm]}}
=====KVM shrink nested LVM=====
**Note! Backup your data first!**

  * Remove content in VM. Free some space, reduce filesystems, logical volumes etc. For example reduce home directory. <code># log in as root via serial, or via SSH.

umount /home
fsck /dev/mapper/VolGroup-lv_home
lvresize --resizefs -L1G /dev/mapper/VolGroup-lv_home
mount /home</code>
  * If you need to reduce the rootfs, boot from network, usb or cd/dvd. Then resize the filesystem. For example, edit guest to boot from systemrescuecd. <code>
lvresize -r -L8G /dev/VolGroup/lv_root</code>
  * Shrink physical volume. First move LV's to beginning.<code>
pvdisplay -m
pvmove -v /dev/vda2:2296-2551 /dev/vda2:0-255 --alloc anywhere
pvmove -v /dev/vda2:2552-2799 /dev/vda2:256-503 --alloc anywhere
pvmove -v /dev/vda2:10428-12475 /dev/vda2:504-2551 --alloc anywhere
pvresize -v --setphysicalvolumesize 16G /dev/vda2</code>
  * On the KVM host, reduce the LV. <code>lvresize -L16G /dev/vg_kvm1/vmns2</code>
  * On the guest force fsck check at next boot, and reboot. <code>touch /forcefsck
reboot</code>




====Boot guest from systemrescuecd iso====
  * Add cdrom device. <code>virsh edit vmns2
<disk type='file' device='cdrom'>
  <driver name='qemu' type='raw'/>
  <source file='/isos/systemresucecd-x86-2.2.0.iso'/>
  <target dev='hdc' bus='ide'/>
  <readonly/>
  <address type='drive' controller='0' bus='1' unit='0'/>
</disk></code>
  * Boot from cdrom first. <code><os>
  <type arch='x86_64' machine='pc-0.12'>hvm</type>
  <boot dev='cdrom'/>
  <boot dev='hd'/>
</os></code>
  * Boot VM and reduce rootfs. When finished, remove the cdrom device and boot device.




====Auto expand root fs from initrd====
  * See: [[https://github.com/flegmatik/linux-rootfs-resize]] <code>cd /opt
rpm -ivh http://ftp-stud.hs-esslingen.de/pub/epel/6/i386/epel-release-6-8.noarch.rpm
yum install git parted cloud-utils
git clone https://github.com/flegmatik/linux-rootfs-resize.git
cd linux-rootfs-resize
./install</code>