:: [DNG] make-rc: A parallel (as in ma…
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Author: Alejandro Colomar (man-pages)
To: Debian Ecosystem Init Diversity Team, Ian Jackson, Benda Xu, Adam Borowski, Vincenzo (KatolaZ) Nicosia, Mark Hindley, Mark Hindley, Devuan (Debian is Not GNOME), Randy Westlund, linux-man, help make
CC: Alejandro Colomar
Subject: [DNG] make-rc: A parallel (as in make(1)) alternative to sysv-rc
Hi all,

Most of you I added you to this email because I found you on the
maintainers list for the Debian sysv-rc package (now dead for a long time).
I also CCd Devuan, since I hope you'll be interested in this little
project of mine.
I also CCd linux-man@, since there's not many people listening there,
and not much traffic these days so I hope you won't be angry for this
little bit of spam; and I hope some good guys reading that list may have
some comments on this. Sorry again for the bit of spam.
I also CCd help-make@. I (ab)used your software in a way that it was
never designed to; not sorry for that; I'll say it was the original Unix
authors' fault for designing such (ab)usable tools :). Maybe you're
interested in this thread, maybe you don't care, but I'll CC you in case
some of you may be interested in this.
And finally, Randy, as you asked, I'll CC you for news on this.
Anyone not interested in follow-ups, please email me, and I'll try to
remove from CC.

So, last friday (yes, that's New Year's Eve), I was reading something,
and got this idea... the main valid claim for systemd is that it blows
away competition in terms of performance? Full parallelization? Knows
about dependencies? I don't know too much of systems; I know some basic
stuff, but I'm mostly a C programmer, so I don't know init(1)... okay.
But since I program, I sure know the good ol' make(1). It's old, and
it's good at fully parallelizing _everything_. Dependencies? sure;
fast? sure; parallel? sure; simple? sure; a bit bloated? GNU make maybe,
especially for init(1), but far from systemd(1):

$ ls -lh $(realpath $(which systemd make bash sh 2>/dev/null))
-rwxr-xr-x 1 root root 1.2M Dec 15 00:43 /usr/bin/bash
-rwxr-xr-x 1 root root 123K Nov 3 11:51 /usr/bin/dash
-rwxr-xr-x 1 root root 235K Apr 10 2021 /usr/bin/make
-rwxr-xr-x 1 root root 1.8M Nov 19 21:11 /usr/lib/systemd/systemd

So, if the problem is that the rc scripts don't run parallel and don't
know about exact dependencies from each-other, let's rewrite that part
and only that part of the system with make(1); that was the idea. Don't
touch init, don't touch the scripts themselves... only the part that
decides on which order to run them. That's the idea.

I decided to start with a clean install of Devuan (since I'm a Debian
user, and I'm used to it; it might have been easier to start with a
smaller system, but I might have found other issues in the middle; I
know that the only difference in Devuan is sysvinit, which is what I
want). The install has XFCE and sysvinit as options. I wanted the
system to have GUI, so that if I can boot XFCE with it, I can boot
anything (except maybe for the bad boy, GNOME, but I don't even like it).

I wrote a couple of scripts to port the existing rc system to my
make-based rc system. The script didn't touch the old one, in case I
needed it to boot if I screwed something, of course. One script creates
the makefiles without declaring the dependencies between them, and then
another makefile creates the dependencies to match the current boot
order (allowing for the same level of parallelization that the current
semi-parallel rc script uses). From there, one could analyze the
dependencies to remove some that are incorrect, and make it faster, but
since I don't know the real dependencies, I didn't want to break stuff.

So, here go the scripts:

====================== script1_basicmk.sh ========================

find /etc/rc[0123456S].d/[KS]* \
|sed s,/etc/rc..d/...,, \
|sort \
|uniq \
|while read x; do\

    test -e $mk \
        && continue;

    >$mk cat <<EOF
.PHONY: K$x S$x

: K$x

: S$x

    /etc/init.d/$x stop

    /etc/init.d/$x start

    find /etc/rc[0123456S].d/K*$x 2>/dev/null \
    |sed s,/etc/rc,, \
    |sed s,.d/K.*,, \
    |sort \
    |tac \
    |while read n; do \
        sed -i "/: K$x$/s/^/$n /" $mk;

    find /etc/rc[0123456S].d/S*$x 2>/dev/null \
    |sed s,/etc/rc,, \
    |sed s,.d/S.*,, \
    |sort \
    |tac \
    |while read n; do \
        sed -i "/: S$x$/s/^/$n /" $mk;

    sed -i "s/ *:/:/" $mk;
    sed -i "/^:/d"    $mk;

===================== script2_deps.sh ===================

find /etc/rc.mk.d/*.mk \
|sed s,/etc/rc.mk.d/,, \
|sed s,.mk$,, \
|sort \
|while read x; do\

    for n in 0 1 2 3 4 5 6 S; do \
        K=$(find /etc/rc$n.d/K??$x 2>/dev/null \
            |grep -o /K.. \
            |sed s,/K0*,,);
        test -z "$K" || test $K -eq 1 \
            && continue;
        k=$(printf %02d $(($K - 1)));

        find /etc/rc$n.d/K$k* \
        |sed s,/etc/rc$n.d/K$k,,;
    done \
    |sort \
    |uniq \
    |while read dep; do \
        echo K$dep;
    done \
    |xargs echo \
    |while read Kdeps; do
        test -z "$Kdeps" \
            && break;

        >>$mk cat <<-EOF

        K$x: $Kdeps

    for n in 0 1 2 3 4 5 6 S; do \
        S=$(find /etc/rc$n.d/S??$x 2>/dev/null \
            |grep -o /S.. \
            |sed s,/S0*,,);
        test -z "$S" || test $S -eq 1 \
            && continue;
        s=$(printf %02d $(($S - 1)));

        find /etc/rc$n.d/S$s* \
        |sed s,/etc/rc$n.d/S$s,,;
    done \
    |sort \
    |uniq \
    |while read dep; do \
        echo S$dep;
    done \
    |xargs echo \
    |while read Sdeps; do
        test -z "$Sdeps" \
            && break;

        >>$mk cat <<-EOF

        S$x: $Sdeps

    for n in 0 1 2 3 4 5 6 S; do \
        test -e /etc/rc$n.d/S01$x \
            || continue;
        K=$(find /etc/rc$n.d/K* 2>/dev/null \
            |grep -o /K.. \
            |sed s,/K,, \
            |sort \
            |uniq \
            |tac \
            |head -n1)
        test -z "$K" \
            && continue;
        k=$(printf %02d $K);

        find /etc/rc$n.d/K$k* \
        |sed s,/etc/rc$n.d/K$k,,;
    done \
    |sort \
    |uniq \
    |while read dep; do \
        echo K$dep;
    done \
    |xargs echo \
    |while read Kdeps; do
        test -z "$Kdeps" \
            && break;

        >>$mk cat <<-EOF

        S$x: $Kdeps

I know some stuff could go into functions to make them shorter, and
probably some comments could also help, but I wrote them fast, just to
have some proof of concept, and later I could makes them nicer. Special
thanks to Doug for creating pipes, I love them :)

The One Makefile To Rule Them All is the following:

================ /etc/rc.mk.d/Makefile ================
MAKEFLAGS += --no-builtin-rules
MAKEFLAGS += --no-builtin-variables

.PHONY: all 0 1 2 3 4 5 6 S

all: 5

0 1 2 3 4 5 6 S:

include /etc/rc.mk.d/*.mk

And then a sample file (created by the above scripts) is:

================ /etc/rc.mk.d/vboxadd.mk ===============
.PHONY: Kvboxadd Svboxadd

0 1 6: Kvboxadd

2 3 4 5: Svboxadd

    /etc/init.d/vboxadd stop
    sleep 1

    /etc/init.d/vboxadd start
    sleep 1

Kvboxadd: Kalsa-utils Kbrightness Kelogind Knetwork-manager
Kpulseaudio-enable-autospawn Ksaned Kslim Kspeech-dispatcher Kurandom

Svboxadd: Sconsole-setup.sh

I added the sleep 1 for debug; the rest is the output of the scripts.

As you can see I kept the K... and S... syntax of rc scripts. However,
instead of a symlink, now there's a makefile declaring dependencies and
calls directly the script with no symlink. Now all makefiles are in a
single directory (I found it simpler this way), but we could think of a
different structure if it's better. These makefiles (or more
technically, parts of a makefile), resemble the systemd service files,
where each one declares what should have already run before start and
before kill, and also contains the info about which runlevels want this
(both S and K).

Because of the script, and because some scripts used .sh extension and
some others didn't, there are some traces of that in the names of the
targets; nothing really problematic, only ugly. I could have removed
it, but it was more work, and I noticed late.

I only had to manipulate a single line from only one of these makefiles
after running the scripts, but that I'll keep if for later; it was
about dependencies, because there was a missing number in one of the
runlevel dirs (no jump from S02 to S04 in one of the dirs, no S03)

And finally, to run all this madness, I had to tweak /lib/init/rc a
little bit:

diff --git a/rc b/rc
index 5e7f3a4..e1ffa31 100755
--- a/rc
+++ b/rc
@@ -60,7 +60,7 @@ export VERBOSE
  # insserv package to be enabled. Boot concurrency also requires
  # startpar to be installed.
  test -s /etc/init.d/.depend.boot  || CONCURRENCY="none"
  test -s /etc/init.d/.depend.start || CONCURRENCY="none"
  test -s /etc/init.d/.depend.stop  || CONCURRENCY="none"
@@ -168,7 +168,10 @@ then

-       if [ makefile = "$CONCURRENCY" ]
+       if [ makefile2 = "$CONCURRENCY" ]
+       then
+               make -C "/etc/rc.mk.d/" "$runlevel"
+       elif [ makefile = "$CONCURRENCY" ]
                 if [ S = "$runlevel" ]

I'd like to know your thoughts about this. If it seems like it could be
a good replacement for sysv-rc (for Devuan; I guess for Debian it's too
late) I'd like to know. Or if you think it can be a good thing but
needs some polish, I'd like to hear it too. It's just a proof of
concept after 2 days of having had fun with it :)

I'd like it to be able to compete in terms of performance with
systemd(1), so that we could possibly take over it, but hey, that's only
a hope.

And now I'll tell you a bit about the outcome I had: I booted with this
configuration, and I first got into single-user mode, which I don't yet
understand why it happened (there's probably something I didn't get
right, but no real blocking problem, I guess). But then, after the
typical type password or ^D to continue, I pressed ^D, and I got a shiny
XFCE GUI completely wirking. Not bad for this prototype, I'd say. I'd
like some help to polish this, if you may.

Happy new year!


Alejandro Colomar
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/