allow kameleon to start over from a fresh vm even when using checkpoints

[npf]

I want to enable checkpoints, but I don't want to reuse previous checkpoints.

This should run a fresh VM and keep checkpoints for a later use:
$ kameleon build --enable-checkpoint receipe.yaml

This only should reuse existing checkpoints:
$ kameleon build --enable-checkpoint --from-checkpoint=<...> receipe.yaml

For ref, the current output of the first command, with existing checkpoints:

$ kameleon build --enable-checkpoint receipe.yaml
Starting recipe consistency check
Resolving variables
Creating kameleon build directory : /home/neyron/scm/digitalis/kameleon-g5k/build/idall-jessie-x64-std
Starting build recipe 'idall-jessie-x64-std.yaml'
Starting process: "bash"
[local] The local_context has been initialized
Restoring last build from step : 4f7c08edc701
[local] 0%...10%...20%...30%...40%...50%...60%...70%...80%...90%...100%
[local] Restoring snapshot 7dab1bf2-65ed-4a24-9f6b-a2378b993362
Step 1 : bootstrap/_init_bootstrap/_init_0_enable_checkpoint
--> Running the step...
Step _init_bootstrap took: 0 secs
Step 2 : bootstrap/enable_checkpoint/enable_checkpoint
--> Running the step...
Step enable_checkpoint took: 0 secs
Step 3 : bootstrap/prepare_virtualbox/download_boot2kameleon_iso
--> Using checkpoint
Step 4 : bootstrap/prepare_virtualbox/create_vdi_disk
--> Using checkpoint
Step 5 : bootstrap/prepare_virtualbox/register_vm
--> Using checkpoint
Step 6 : bootstrap/prepare_virtualbox/generate_ssh_keys
--> Using checkpoint
Step 7 : bootstrap/prepare_virtualbox/create_ssh_config
--> Using checkpoint
Step prepare_virtualbox took: 0 secs
Step 8 : bootstrap/start_virtualbox/start_vm
--> Running the step...
[local] Starting virtualbox...
[local] Waiting for VM "idall-jessie-x64-std_f8375b4b598c" to power on...
[local] VM "idall-jessie-x64-std_f8375b4b598c" has been successfully started.
[local] Waiting for SSH to become available for out_context...(44s)^C
Starting process: "bash"
Error occured when executing the following command :

[mickours]

I don't really understand the use case and/or the problem.

If you do not want kameleon to use the previously generated checkpoint just do:

kameleon build --clean receipe.yaml
kameleon build --enable-checkpoint receipe.yaml

It will start from a fresh VM and create new checkpoints.

The --enable-checkpoint option find automatically the last changed step and use the right checkpoint accordingly. The --from-checkpoint option was made to override this behaviour when the user want to force a selected checkpoint.

If you problem is that some steps should be done again even when using checkpoint you should use the - on_checkpoint: redo hook in your step definition. This is not documented (I just add an issue #65) but you can see examples here:
https://github.com/oar-team/kameleon-recipes/search?utf8=%E2%9C%93&q=on_checkpoint&type=Code

Thanks for reporting, I don't know if I really answer your question, do I?

[npf]

It is indeed just an ergonomic problem. A command ought to be the most natural from a user's perspective, which I'm not completely convinced it is the case currently for checkpoints ;-)
At least some documentation must be added indeed.

Also the current usage message must be reworked to make the grammar of checkpoint related options more readable.