runsvdir@: add

2 files changed, 52 insertions, 0 deletions

diff --git a/runsvdir@/README.md b/runsvdir@/README.md
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+# runsvdir@ : runit compatibility
+This is a transitional service so you can migrate to nitro one piece
+at a time. Under normal runit-init usage, /etc/runit/2 will exec into
+a runsvdir against your selected runlevel. This essentially does the
+same work, except the runlevel is selected by the @ target (you can
+select `current` to emulate typical runit setups).
+
+For example, here's what `pstree` looks like on an runit system:
+```
+runit───runsvdir─┬─runsv─┬─service1
+                 │       └─logger
+                 ├─runsv─┬─service2
+                 │       └─logger
+                 └─runsv─┬─service3
+                         └─logger
+```
+
+A first step towards moving towards nitro can look like so: you swap
+out /sbin/init and /sbin/halt to nitroctl, setup the special SYS
+service, and then use this service as `runsvdir@default` (or
+`@current`). At this point, your `pstree` should look like this:
+
+```
+nitro───runsvdir─┬─runsv─┬─service1
+                 │       └─logger
+                 ├─runsv─┬─service2
+                 │       └─logger
+                 └─runsv─┬─service3
+                         └─logger
+```
+
+At this point, you can freely control the system using both
+supervisors, picking which service to move over and when.
+
+This service pre-supposes that you are running Void Linux. If this is
+not the case, your runlevels may not be under
+`/etc/runit/runsvdir`. In that case, you will want to set `RUNSVDIR`
+to where your runlevels reside in `./conf`. If your runit setup does
+not use runlevels and only uses (for example) `/service` directly, you
+can set `RUNSVDIR` to the parent directory of your "runlevel". `/`
+should work.
diff --git a/runsvdir@/run b/runsvdir@/run
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+++ b/runsvdir@/run
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+#!/bin/sh
+
+runlevel="$1"
+[ -f ./conf ]      && . ./conf
+[ -f ./conf."$1" ] && . ./conf."$1"
+
+# set this in ./conf if your system keeps runlevels elsewhere
+: ${RUNSVDIR:=/etc/runit/runsvdir}
+[ -d "$RUNSVDIR/$runlevel" ] || runlevel=current
+
+exec runsvdir -P "$RUNSVDIR/$runlevel"