Comment 13 for bug 694772

I find the touch /var/run/init.upgraded approach much less intrusive; I discussed various approaches with Debian, and none is entirely satisfactory. Apparently some filesystems wont be able to restore the new versions of the files if they aren't closed properly, and an unclean shutdown would cause these systems to keep the old libs.

Another issue is that upgraded systems continue running the old libc6 until reboot (at least their init does).

However since bug #672177 explains that upstart basically stopped honoring SIGTERM some time ago due to a broken merge, whatever short term solution which avoids using telinit will be fine.