Comment 4 for bug 348455

I think this is a critical feature: working re-exec is a must for proper Upstart upgrades. Currently upgrade from older Upstart versions to 0.6 are fatal to the system: new initctl won't talk to the old and still running Upstart and even a simple reboot may be a problem. When upgrading one 0.6.x Upstart to other 0.6.x only the 'clients' are really upgraded, the old init will be running until the reboot. That is not a big problem for a desktop or embedded systems, but servers should not require reboot after upgrade.

That is why I have started an Upstart branch (lp:~jajcus-jajcus/upstart/state-save) to implement full state saving and re-exec with state transfer. I hope this can help making Upstart a usable (in all cases) replacement for SysVinit.