How to create a template from a OpenVZ container with the ploop layout?

Question

How to create a template from a OpenVZ container with the ploop layout? The current implementation of Create Template feature works only for the containers with simfs layout.

Answer

Since RHEL6-based OpenVZ kernel, i.e. 042stabXXX OpenVZ starts support container-in-a-file technology (ploop). It can be enabled on the node settings page Dashboard > Nodes > node_name > click icon:

If such option is enabled, OpenVZ creates an image file inside of the container private directory - /vz/private/CTID/root.hdd/ in order to store the data. In that case, feature is not available and template should be created manually as per steps below:

1. Connect via SSH to the OpenVZ server where the source template container is running
2. Stop the source template container via SolusVM
3. Create a directory for mountpoint, e.g.:

   # mkdir /templatemnt

4. Mount the image of the source container CTID:

   # mount -t ploop /vz/private/CTID/root.hdd/DiskDescriptor.xml /templatemnt

   Note: CTID should be replaced with the actual ID of the source container

5. Change directory location and create a template as per command below, e.g. for CentOS 7:

   # cd /templatemnt
   # tar --numeric-owner --ignore-failed-read -czpf /vz/template/cache/centos-7-x86_64-custom.tar.gz ./*

   Note: The template file name should be as per the following syntax: distributive-version-arch-specs.tar.gz

6. Unmount the ploop device:

   # cd ~
   # umount /templatemnt

7. Upload the template file on the Master server and configure the template