postfix started in single user mode during upgrade

[Phillip Susi]

I shutdown my server to single user mode and ran a dist-upgrade. The postfix postint started the daemon, even though it is not supposed to be running in single user mode.

[Phillip Susi (psusi)]

Just created a fresh install of 13.10 in a vm, swapped /etc/apt/sources.list to trusty, shutdown to single user mode, confirmed with runlevel that the system was in single user mode, and ran apt-get install postfix to upgrade it, and sure enough, it it started postfix.

[Phillip Susi (psusi)]

It looks like the problem is in invoke-rc.d: manually running invoke-rc.d postfix restart, while in single user mode, starts postfix.

[Steve Langasek (vorlon)]

When you say "single user mode", is that runlevel 1 or runlevel S?

I can confirm that, because update-rc.d creates a K link for postfix in /etc/rc1.d, but not in /etc/rcS.d, invoke-rc.d will not detect a "policy" for the init script in runlevel S and will assume that it should take the requested action.

It's probably a good idea to file this bug upstream with Debian; I doubt we want to diverge from upstream on this corner case, considering how hairy the code is.

[Phillip Susi (psusi)]

I'm a little confused. I thought that runlevel S was a pseudo runlevel that only ever contained S links that were only called during initial boot, no matter what runlevel you were going to, and that a shutdown or booting with the 's' argument transitioned you to runlevel 1. As such, update-rc.d isn't supposed to create a K link in /etc/rcS.d, since the rc scripts would never use it.

invoke-rc.d has this comment:

### LOCAL INITSCRIPT POLICY: Enforce need of a start entry
### in either runlevel S or current runlevel to allow start
### or restart.

That seems pretty clear: there is no S link for postfix in either rcS.d nor rc1.d, so it shouldn't be starting it.