launchd (Mac OS X Tiger startup)

With Mac OS X Tiger, "launchd" is now pid 1:

$ ps ajxw |sort -n +1| head
USER       PID  PPID  PGID   SESS JOBC STAT  TT       TIME COMMAND
root         1     0     1 166ae88    0 S<s   ??    0:02.76 /sbin/launchd
root        28     1    28 166ac60    0 Ss    ??    0:00.01 /sbin/dynamic_pager -F /private/var/vm/swapfile
root        32     1    32 166ab4c    0 Ss    ??    0:01.79 kextd
root        36     1    36 166aa38    0 Ss    ??    0:06.28 /usr/sbin/configd
root        37     1    37 166a924    0 Ss    ??    0:01.23 /usr/sbin/coreaudiod
root        38     1    38 166a810    0 Ss    ??    0:01.62 /usr/sbin/diskarbitrationd
root        39     1    39 166a6fc    0 Ss    ??    0:00.06 /usr/sbin/memberd -x
root        40     1    40 166a5e8    0 Ss    ??    0:00.95 /usr/sbin/securityd
root        42     1    42 166a4d4    0 Ss    ??    0:01.50 /usr/sbin/notifyd
 

Quite obviously, it is filling the role that init plays on System V systems. It is also intended to replace rc scripts (from the man page):

NOTES
     In Darwin it is preferable to have your daemon launch via launchd
     instead of modifying rc or creating a SystemStarter Startup Item.

     At some point in the future, we hope to completely phase out the
     use of rc.
 

It's even taken over some things that used to be done by cron such as running "perodic":

$ cat /etc/crontab
# The periodic and atrun jobs have moved to launchd jobs
# See /System/Library/LaunchDaemons
#
 

Oddly, you'll find apparent duplication of content in /System/Library/LaunchDaemons and /etc/xinetd.d files.

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