Slack also support sub-roles for specific parts of an application, and both pre- and post-install scripts.

Still said there are alternatives to Slack, the most obvious being operating system packages, but one advantage of Google's system is there is "no intermediate binary compact form" of the Slack role.

"So it's reasonably easy to go poke around with just the bit you need without going and rebuilding an entire RPM," he said.

While there is no concept of rolling back a Slack role, if something is broken "you fix it and redeploy it everywhere".

"If you really regret that a machine is not an LDAP slave for instance, you have a repeatable operating system install [so] rebuild it for whatever it was meant to be," Still said. "We can get a new server up in probably half an hour."