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defer-
Tux's lil' helper
Joined: 11 Jun 2007
Posts: 140
Location: Finland
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 Posted: Fri Sep 19, 2014 12:18 pm Post subject: How does gentoo startup / init work? |
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I would like to create custom init to get fast startup and shutdown times. I created sinit[1] ebuild and installed it. I chaged savedconfig and created /etc/rc script. My current setup boots fine to X but shutdown and module loading doesn't work.
How does Gentoo sysvinit/openrc startup work? What does init execute and how does openrc execute init scripts on startup or shutdown? What is needed for working system?
[1] http://git.suckless.org/sinit/
[2] /etc/rc
| Code: |
#!/usr/bin/env bash
if [[ "$1" = "start" ]]; then
echo "Starting up Gentoo Linux"
mkdir -p /proc
mkdir -p /sys
mount -n -t proc -o nosuid,noexec,nodev proc /proc
mount -n -t sysfs -o nosuid,noexec,nodev sysfs /sys
mount -n -t tmpfs -o nosuid,mode=0755 dev /dev
mkdir -p /dev/pts
mount -n -t devpts -o gid=5,mode=0620 devpts /dev/pts
echo Running smdev
smdev -s
echo Setting smdev as the kernel hotplug
echo /bin/smdev > /proc/sys/kernel/hotplug
echo Loading kernel modules
find /sys -name 'modalias' -type f -exec cat '{}' + | sort -u | xargs modprobe -b -a 2>/dev/null
echo Remounting root as read-write
mount -o remount,rw /
echo Mounting filesystems
mount -a
hostname dfr-laptop
/sbin/agetty --noclear 38400 tty1 linux &
/sbin/agetty --noclear 38400 tty2 linux &
elif [[ "$1" = "reboot" ]]; then
echo "Rebooting Gentoo Linux"
killall5 -s KILL
echo Remounting root as read-only
mount -o remount,ro /
echo Unmounting filesystems
umount -a
sync
sleep 1
wait
reboot
elif [[ "$1" = "shutdown" ]]; then
echo "Shutting down Gentoo Linux"
killall5 -s KILL
echo Remounting root as read-only
mount -o remount,ro /
echo Unmounting filesystems
umount -a
sync
sleep 1
wait
halt
else
echo "Unknown command"
fi
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steveL
Watchman
Joined: 13 Sep 2006
Posts: 5153
Location: The Peanut Gallery
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| Posted: Fri Sep 19, 2014 10:27 pm Post subject: |
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First off, lose the awfully fscked-up shebang: #!/usr/bin/env bash is wrong on so many levels. Just use #!/bin/sh and learn to write portable sh.
Most of that looks ok, but I'd separate out into functions, and use a simple case. |
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steveL
Watchman
Joined: 13 Sep 2006
Posts: 5153
Location: The Peanut Gallery
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| Posted: Sun Oct 12, 2014 12:56 am Post subject: Re: How does gentoo startup / init work? |
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| defer- wrote: | | How does Gentoo sysvinit/openrc startup work? What does init execute and how does openrc execute init scripts on startup or shutdown? What is needed for working system? |
As with every Linux (and indeed Unix that I know of), "init" means pid1: it doesn't do very much, but it is configured via /etc/inittab -- the file is pretty well-commented. Though you really shouldn't edit it in general, in your case you likely need to.
pid1 must be robust, and simply-coded, since it must run for the entire uptime of the machine. It is the first process started by the kernel, and if it exits (or crashes), the kernel panics (ie: completely halts) and all your in-flight data is lost, FS may be corrupted, etc. ie: Game Over.
For this reason, it's not worth redoing pid1: complexity is much better handled elsewhere, in the default case by openrc (command: /sbin/rc) which you can see is run by init on entry to the various run-levels. So we still use sysvinit, since there's nothing more that would sanely be added to pid1. ie: sys-apps/sysvinit
Read man 8 init for more information; man runscript and man rc if you want to know more about openrc. |
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