Supporting Dynamic root-disk in LVM-enabled Templates - EL7 Edition

In my previous article,  Supporting Dynamic root-disk in LVM-enabled Templates, I discussed the challenges around supporting LVM-enabled VM-templates in cloud-based deployments of Enterprise Linux 6 VMs. The kernel used for Enterprise Linux 7 distributions makes template-based deployment of LVM-enabled VMs a bit easier. Instead of having to add an RPM from EPEL and then hack that RPM to make it support LVM2-encapsulated root volumes/filesystems, one need only ensure that the cloud-utils-growpart RPM is installed and do same launch-time massaging via cloud-init. By way of example:

#cloud-config
runcmd:
  - /usr/bin/growpart /dev/xvda 2
  - pvresize /dev/xvda2
  - lvresize -r -L +2G VolGroup00/logVol
  - lvresize -r -L +2G VolGroup00/auditVol

Will cause the launched instance to:

1. Grow the second partition on the boot disk to the end of the disk
2. Instruct LVM to resize the PV to match the new partition-size
3. Instruct LVM to grow the VolGroup00/logVol volume — and the filesystem on top of it — by 2GiB
4. Instruct LVM to grow the VolGroup00/auditVol volume — and the filesystem on top of it — by 2GiB

Upon login, the above launch-time configuration-actions can be verified by using `vgdisplay -s` and `lvs --segments -o +devices`:

# vgdisplay -s
  "VolGroup00" 29.53 GiB [23.53 GiB used / 6.00 GiB free]
# lvs --segments -o +devices
  LV       VG         Attr       #Str Type   SSize Devices
  auditVol VolGroup00 -wi-ao----    1 linear 8.53g /dev/xvda2(2816)
  auditVol VolGroup00 -wi-ao----    1 linear 2.00g /dev/xvda2(5512)
  homeVol  VolGroup00 -wi-ao----    1 linear 1.00g /dev/xvda2(1536)
  logVol   VolGroup00 -wi-ao----    1 linear 2.00g /dev/xvda2(2304)
  logVol   VolGroup00 -wi-ao----    1 linear 2.00g /dev/xvda2(5000)
  rootVol  VolGroup00 -wi-ao----    1 linear 4.00g /dev/xvda2(0)
  swapVol  VolGroup00 -wi-ao----    1 linear 2.00g /dev/xvda2(1024)
  varVol   VolGroup00 -wi-ao----    1 linear 2.00g /dev/xvda2(1792)