Date: Mon, 30 Nov 1998 11:31:48 +1030 From: Greg Lehey <grog@lemis.com> To: "Marko's Work" <marko@websorcery.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Curious about what happens during boot. Message-ID: <19981130113148.H831@freebie.lemis.com> In-Reply-To: <01be1bfa$fdc6f100$ba80b7d1@vidbox>; from Marko's Work on Sun, Nov 29, 1998 at 07:47:22PM -0500 References: <01be1bfa$fdc6f100$ba80b7d1@vidbox>
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On Sunday, 29 November 1998 at 19:47:22 -0500, Marko's Work wrote:
> With FreeBSD, what script is run first (upon boot) in the /etc directory?
> With dos, config.sys and autoexec.bat are run after
> command.com, but in FreeBSD what comes after running the kernel?
> I would like to trace the whole procedure to become familiar with it.
This is a borderline -questions/-hackers question. I'll deal with it
here.
The first process that UNIX starts is process 0 (strangely enough).
Nowadays it doesn't do much more than spawn process 1, which is called
init. From the source code (/usr/src/sbin/init/init.c):
/*
* The mother of all processes.
*/
Roughly, init performs the following functions on startup:
1. Initializes itself, including ensuring that it's process 1,
setting the way it opens the system log file, ensuring that it's a
session leader and running as root, and looking at some of the
boot flags, including -s (single user) and -f (fast boot).
2. If you specify -s, it will go into single user mode by spawning a
copy of itself, which will start a shell. You do what you want
and exit the shell. Then the original init continues.
3. Next it starts a shell which runs the script /etc/rc, and waits
for it to complete. You can take a look at /etc/rc to see what it
does: it reads in the following scripts:
/etc/rc.conf to get configuration variables
/etc/rc.serial to configure serial devices,
/etc/rc.pccard to set up PC-cards (laptop plugin cards),
/etc/rc.network to start the network services
/etc/rc.i386 for processor-specific startup
/etc/rc.local for site-related startup files
4. Finally it looks at the file /etc/ttys and starts all the gettys
described there.
Greg
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