Clone vm-bhyve cloudinit images

USAGE: img-clone <template> <target> <userdata> [<instance_config>]

img-clone provides a utility to clone vm-bhyve cloud-init enabled images and dynamically update the cloud-init user data (re-generating the seed.iso)

The source template should be a cloud-init enabled vm-bhyve instance (the utility will use the latest snapshot by default - to use a specific snapshot this should be specified explicitly as template@snapshot)

A new vm-bhyve instance target will be created (using vm clone) and userdata copied into the .cloud-init folder and the the seed.iso image updated with the contents of the .cloud-init folder.

userdata can either be specified as a file (or - for stdin) which will be written as user-data, or can be a directory which will be copied recursively into the .cloud-init folder (which allows additional files to be included in the cloud-init configuration).

If instance_config is specified (either a file or - for stdin) it is written to the .cloud-init folder as CONFIG (this is to allow a common userdata config to be used for multiple instances and just specify separate instance_config)

This approach is much faster than using vm create with a cloud image which uses qemu dd to copy the disk image rather than a zfs clone (which is pretty much instant).

The source vm-bhyve instance should be configured to support cloud-init (vm create -C ....) and the OS image also cloud-init enabled. For FreeBSD it is possible to use the (very simple) bhyve-cloudinit rc.d script included in thsi repository. This will mount the cdrom, set hostname from the meta-data file and run the user-data script. There is very rudimentary support for cloud-config files (add ssh keys, install packages, and runcmd) but this doesnt parse the yaml file properly so will fail with anything unexpected. The utility is mostly intended to just run a shell-script in user-data.

When configuring the source template make sure that there are no artefacts left in the instance (ssh host keys, config files, logs etc) and that the /firstboot flag is set.