Creating a template from an OpenVZ container is a very manual process. My biggest problem is that you have to have root access to the Proxmox hardware node in order to create a tar from the root of the CT. See How to make a new OpenVZ template for more information on manually creating a template.
I created a small code patch for the Proxmox API and web GUI to add a ‘create template’ feature for CTs. The code adds a context menu entry when you right click on a CT in the Proxmox web GUI.
Before using the feature, the CT must be shut down and any network interfaces removed. The feature presents the user with a dialogue box requesting which storage device the template should be saved to, and what it should be called.
Once the storage has been selected and the template has been given a name, a new ‘create template’ task is created which archives the root directory of the selected container and adds it to the cache folder of the selected storage.
The changes were declined by the Proxmox team on the grounds that creating a template is a technical process and may not result in creating a working, cloned instance. In addition, it is very easy to leave sensitive information in the CT which is the source of the template – all data on the CTs file system will be archived into the template making it available the next time a CT is created. If SSH keys are left on the CT, for example, then they will be available in the new CT also.
Because the feature was not accepted into the main distribution of Proxmox, I will maintain it myself and manually apply the patches to my Proxmox servers after every update. I have created a public repository on my Gitlab server that holds the git patch file which is available for everyone.
If you accepts the risks mentioned above, and are happy to hack away at your Proxmox binaries, then you are welcome to try the patch for yourself.
You can download the patch and get more information on my public Proxmox Github page.
I should mention that this patch may not always be up to date. In addition, this is changing the actual Proxmox distribution files and as such may have unintended side effects. Please use these patches with caution and only in your development environments.