question \ information request on init \ boot sequence when using initrd

From: Amit D Chaudhary (amit@muppetlabs.com)
Date: Mon Mar 26 2001 - 21:41:17 EST


Hi,

We(my team) had some questions regarding booting from initrd and using
/linuxrc. It will help someone(David, Werner,...) can give their
thoughts on this.

To put it in brief, since running sbin/init from /linuxrc as resulting
in init not having PID 1 and thereby not doing some initialization as
expected.

Thereby instead of loading running /sbin/init, we just set
/proc/sys/kernel/real-root-dev to /dev/ram0's value which then does the
following
runs 2 statements in init/main.c to unlock_kernel and free init memory
and then run sbin/init.
This results in /sbin/init running fine.

Is this ok or should be modify /sbin/init to run properly inspite of PID
<> 1 or is there a 3rd way of doing this?

Thanks
Amit

This is on linux-2.4.1 kernel running on PPC.
/linuxrc is as follow:

../bin/mount -t ramfs none tmp_rootfs

#untar'ing the new root.
../bin/tar -b 512 -zxf /dev/mtd1

mkdir initrd
../bin/pivot_root . initrd

exec sbin/chroot . sbin/init.new 3 <dev/console >dev/console 2>&1

The above results in init running with PID != 1 and thereby skipping
some relevant processing my default. see ps output below:

Instead of the "chroot" above is changed to following
exec sbin/chroot . sh -c 'bin/mount proc proc -t proc; echo 0x01000000 >
proc/sys/kernel/real-root-dev'
And linuxrc exits

(none):root> ps -e
   PID TTY TIME CMD
     1 ? 00:00:04 swapper
     2 ? 00:00:00 keventd
     3 ? 00:00:00 kswapd
     4 ? 00:00:00 kreclaimd
     5 ? 00:00:00 bdflush
     6 ? 00:00:00 kupdate
     7 ? 00:00:00 mtdblockd
     8 ? 00:00:00 init
    26 ? 00:00:00 sh
    39 ? 00:00:00 portmap
    50 ? 00:00:00 ypbind
    51 ? 00:00:00 ypbind
    84 ? 00:00:00 inetd
    93 ? 00:00:00 syslogd
   100 ? 00:00:00 klogd
   119 ? 00:00:00 ps

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This archive was generated by hypermail 2b29 : Sat Mar 31 2001 - 21:00:15 EST