Noble Numbat stemcell no longer uses `runit` to launch the agent

[aramprice]

Currently the bosh-agent is started using a separate process manager runit.

This issue proposed removing runit in favor of the existing process manager on Ubuntu, systemd.

Having a single process management system allows that system to optimize startup across all processes in the system hopefully speeding up the time-to-ready for the whole system.

This is related to though not dependent on replacing monit (also with systemd).

[ramonskie]

when moving the agent and monit to systemd. i noticed that chpst is used in almost all bosh releases which will run a program with the user vcap chpst is a component from runit. so we still need to have runit. there is an option to replace it chpst -u vcap:vcap with:

• runuser- u vcap -g vcap executable
• systemd-run --uid vcap --guid vcap
• setpriv--reuid vcap --regid vcap

[rkoster]

As discovered by Ramon: the agent also invokes runit directly to start monit: https://github.com/cloudfoundry/bosh-agent/blob/main/platform/monit_retryable.go#L20 This should become configurable similar to: https://github.com/cloudfoundry/bosh-agent/pull/324

[jpalermo]

We should consider what we want to do with bosh-lite too. We could keep runit just on the warden stemcells or we could come up with an alternative (since systemd doesn't run under warden stemcells)

[ramonskie]

in the meantime i have removed the runit units for monit and the agent and converted them to systemd services https://github.com/cloudfoundry/bosh-linux-stemcell-builder/commit/c27910fdf1ee48187ae767edb27df3f5d666b17b