I seem to remember that since SysV init runs services in a serial (not parallel) fashion, you can kill whatever's currently in the foreground with some key combination -- apparently not ctrl-c/z/d though.Searching online has not been fruitful.  Does anyone know whether such a key combo really exists (and if so, what is it)?
Terminate/skip SysV service during boot
debian;sysvinit
sysvinit bugI dug this bit up in a bug that was opened against the sysvinit package in a Debian report which would lead me to believe what you're stating is correct. The bug is titled: sysvinit: Failing to interrupt some script after upgrade and it was part of this Debian Bug report logs - #582442.excerptsince last upgrade (makefile style migration ?) I got strange   behaviour of the boot sequence.If I interupt some script with ctrl+c, the dependency are lost (not fs  mounted, no network, ...).  With the previous version this worked.I interrupt sometimes fsck (when I don't want to wait), now this doesn't  work.Also on my system udev script hang at the end (until there is a  timeout). I often hit ctrl+c to avoid waiting the timeout. This now make  the system not usable.If ctrl+c is not supported anymore, it should blocked to avoid this  strange behaviour.MatthieuFurther down in that thread it states that this functionality was supposedly fixed. I did not follow this thread beyond here, so you might want to dig further.excerptFrom: Ben Hutchings <ben@decadent.org.uk>To: 582442-close@bugs.debian.orgSubject: Bug#582442: fixed in sysvinit 2.88dsf-13.1Date: Sat, 01 Jan 2011 05:47:35 +0000Source: sysvinitSource-Version: 2.88dsf-13.1We believe that the bug you reported is fixed in the latest version ofsysvinit, which is due to be installed in the Debian FTP archive:CONCURRENCY=?I didn't search much further but I believe there is a variable in /etc/init.d/rc that controls concurrency. When this is enabled it sounds like the Ctrl+C feature is disabled. Setting it to none should restore this ability.CONCURRENCY=noneI found that mentioned here,  in this Launchpad bug titled: CONCURRENCY=startpar doesn't work.