system/s6-linux-init: new package = new init system

 This commit touches lots of things at once: it is necessary in order
to maintain consistency. The impacted packages are:

 - s6-linux-init: new package. s6-linux-init mechanism plus
booting policy. s6-linux-init conflicts with sysvinit; you can
have one or the other, depending on what init you want to boot on.
   * s6-linux-init-common: subpackage of s6-linux-init, containing
files used in the s6 supervision tree in both init cases.
Both s6-linux-init and sysvinit depend on s6-linux-init-common.

 - s6: removed s6-svscanboot, which is policy, and only used
in the sysvinit case. The s6 package is pure mechanism now.

 - utmps: adapted to the new location of the supervision tree, and
reliable files provided by s6-linux-init-common. It works as is
with both init systems.

 - gettys-openrc: had to move its invocation from "openrc sysinit"
to "openrc default", because you can't make early gettys with
s6-linux-init (no control over stage 1), and you can't have a
supervision tree before sysinit with sysvinit (because /run is
mounted very late, in boot), so the only solution that works with
both is to make gettys late services.

 - sysvinit: now has s6-svscanboot (starting the s6 supervision
tree from inittab), and a carefully crafted inittab that should
work in all cases. Getting the right order of inittab lines was
NOT easy, and I now hate sysvinit even more than I did before.

 Note that with the current version of apk, you cannot switch from
sysvinit to s6-linux-init, or vice-versa, without an error. apk
says files conflict. Because it adds the new files before removing
the old ones. It should still work with apk -f, because the
.apk-new mechanism makes it so that there's no real collision while
you're switching, but it's still ugly as fuck and needs to be fixed
in apk before we make the switch available to users.

1 files changed, 13 insertions, 7 deletions

diff --git a/system/sysvinit/inittab-2.88 b/system/sysvinit/inittab-2.88
index e96205a06..f170042cf 100644
--- a/system/sysvinit/inittab-2.88
+++ b/system/sysvinit/inittab-2.88
@@ -16,30 +16,36 @@
 # Default runlevel.
 id:3:initdefault:
 
-# System initialization, mount local filesystems, etc.
+# Early system initialization.
 si::sysinit:/sbin/openrc sysinit
 
-# Further system initialization, brings up the boot runlevel.
+# Further system initialization.
+# The distinction between sysinit and boot is totally arbitrary.
+# With the current OpenRC, sysinit does almost nothing and boot
+# does almost everything.
 rc::bootwait:/sbin/openrc boot
 
+# Start the s6 supervision tree.
+s6:12345:respawn:/sbin/s6-svscanboot
+
+# Wait for the supervision tree to be operational before launching services.
+s6n:12345:wait:/bin/sh -c 'until test -s /run/s6_ready ; do sleep 1 ; done'
+
 l0:0:wait:/sbin/openrc shutdown 
-l0s:0:wait:/sbin/halt -hnp
+l0s:0:wait:/sbin/poweroff -df
 l1:1:wait:/sbin/openrc single
 l2:2:wait:/sbin/openrc nonetwork
 l3:3:wait:/sbin/openrc default
 l4:4:wait:/sbin/openrc default
 l5:5:wait:/sbin/openrc default
 l6:6:wait:/sbin/openrc reboot
-l6r:6:wait:/sbin/reboot -fin
+l6r:6:wait:/sbin/reboot -df
 #z6:6:respawn:/sbin/sulogin
 
 # new-style single-user
 su0:S:wait:/sbin/openrc single
 su1:S:wait:/sbin/sulogin
 
-# We now delegate all "respawn" services, including terminals, to s6.
-s6:12345:respawn:/lib/s6/s6-svscanboot
-
 # What to do at the "Three Finger Salute".
 ca:12345:ctrlaltdel:/sbin/shutdown -r now