Add option to disable conda installation when using custom docker images

[hemildesai]

When using a custom docker image as runtime environment, there should be an option to disable the CONDA_INSTALLATION_COMMANDS during setup which the user can configure.

I think setting the value to empty string here when a custom image is present should suffice.

This will also help reduce the startup time.

Let me know your thoughts if this a good idea?

[Michaelvll]

Thanks for raising this @hemildesai! We were installing conda for all clusters to keep environments aligned. We can consider adding a knob in ~/.sky/config.yaml to disable the conda installation for better speed.

In that case, setting CONDA_INSTALLATION_COMMANDS may not be sufficient, as we may need some checks for the default Python version on the system, and not install conda only when python=3.10 to make sure the dependency for skypilot runtime can be correctly installed.

[hemildesai]

@Michaelvll Ah ok, makes sense. I would assume it would require changes to https://github.com/skypilot-org/skypilot/blob/master/sky/skylet/constants.py#L131 as well.

But would be nice to reuse the python environment directly inside the container.

[cblmemo]

This should be fixed by #3874. Closed now