Custom KVM template which is created in CentOS 7 Node is not working in the CentOS 6 Node

Symptoms

• Custom KVM template that has been created in CentOS 7 Node is not working in the CentOS 6 Node with the following error shown on VNC screen:

  CONFIG_TEXT: no bootable device

• The following error can be found in build log:

  CONFIG_TEXT: guestmount: no operating system was found on this disk

• On attempt to view the partitioning on the custom template with the following command, the error is shown as well:

  # virt-filesystems -a windows-2012-server-custom-x86_64-gen2-v2.gz --all --long --uuid -h
  libguestfs: error: /usr/libexec/qemu-kvm exited with error status 1.
  To see full error messages you may need to enable debugging.
  See http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs
  libguestfs: error: guestfs_launch failed.

• When debug is enabled as described above, the error is different:

  # virt-filesystems -a windows-2012-server-custom-x86_64-gen2-v2.gz --all --long --uuid -h
  qemu-kvm: -drive file=windows-2012-server-custom-x86_64-gen2-v2.gz,snapshot=on,cache=writeback,id=hd0,if=none: '' uses a qcow2 feature which is not supported by this qemu version: QCOW version 3

Cause

Template created in CentOS 7 Node supports the qcow2 feature which is not available on CentOS 6.

Resolution

Convert the current template on CentOS 7 node to another format. For that:

1. Log into CentOS KVM node via SSH.
2. Execute the following command to convert the template to another format:

   # qemu-img convert -O qcow2 -o compat=0.10 windows-2012-server-custom-x86_64-gen2-v2.gz /root/windows-2012-server-custom-x86_64-gen2-v2.gz

Sync this template to CentOS 6 Node.

This template should work fine on both CentOS 6 and CentOS 7 Node.

Note: the article assumes that the template name is windows-2012-server-custom-x86_64-gen2-v2.gz. Replace it with a proper name.