Sven> Hi all I wanted to know why that when changing runlevels from Sven> say 2 to 3, the KILL links of _3_ and not 2 get executed before Sven> starting the START links of 3...?
Marshal> I think because K comes before S. So switching run levels Marshal> only runs the scripts in the runlevel dircetory (in your case Marshal> rc3.d). The kill scripts of 2 have already been run, Marshal> presumably when you first boot up, or when you switched to Marshal> runlevel 2. Sven> Hmm, my idea of the K links have been to "clean up" the system Sven> so as to be able to go into a different state / runlevel... but Sven> I am unsure now. Sven> I mean, at that point you're leaving runlevel 2 and it would Sven> only make sense to stop those runlevel's services and not the Sven> new runlevel's, right? Marshal> Maybe, but I think to have what you want, you'll need start Marshal> up scripts and kill scripts for both going into the runlevel Marshal> and leaving the Sven> But at first, the system isn't in any runlevel and hasn't any Sven> services up, and so it won't need to stop anything and thus K Sven> links for runlevel S (or whatever the first actual runlevel is) Sven> don't make sense to me. Sven> Someone please shed some light on this for me as I want to Sven> understand this. What you're missing (and it's easily missed) is that the runlevel changes are _stateless_. It doesn't matter what the _old_ level is, the system will always execute the same scripts upon entering the same (new) level. So, for each level, the K scripts "clean up" everything that is not needed _on the new level_, potentially doing some redundant work (ie. killing servers that are not running because they are not part of the old level). Then the S scripts start everything that is needed, again potentially restarting things that were already active on the old level (although Debian avoids that as a matter of optimization). Why is it this way? Well, there's really no way to tell init to execute programs upon _exiting_ a runlevel, or upon a transition from one level to another; the /etc/inittab that defines runlevels is one-dimensional. So the transition must be defined independently of the old level. -- Ian Zimmerman, Oakland, California, U.S.A. In his own soul a man bears the source from which he draws all his sorrows and his joys. Sophocles.
