[BusyBox] Busybox init.

[Hiroshi Ito]

Hello, 
> Eg:
> initrd's linuxrc last lines...
> 
> cd /root
> pivot_root . initrd
> exec chroot . /sbin/init <dev/console >dev/console 2>&1

  This is your fault.

  this means,
  process of chroot will have pid 1.
  and init will have another.

  my /sbin/init also shell script.

  I put my /sbin/init end of this mail.

  It is on real root filesystem, not in initrd.
  My root filesystem is on /dev/mtdbock/1(on flash) with cramfs
  ( read only )

  You will need explanation to understand my script.
  1.if linux command line argument has argument like "usbroot=0/part2"
    mount usbdisk and boot from there,
    ( I have most of redhat 9 is on usbdisk. )
  2.if there is /initrd/init, execute it.
    ( this for debugging purpos.
      I can easyly download ramdisk with tftp(I use u-boot),so
      when I want to change a /sbin/init, I check it with
      initrd before rewrite flash.)
  3.create root filesystem with tmpfs, and chroot to there,
    then execute init.
    all tmpfs's directory are symlink to cramfs.
    but where I needs to write, create a real directory, but
    contents are symlink to cramfs.
    ( command mkwritable, you see is my program.
      which do like,
        for file in $*; do
	     rm $file; mkdir $file; ln -s /rom/$file/* $file"
	done
      but mkwritable does more, about keep owner, permission, device
      and not only for directory, but files...
      I program it with C. )
  4. /etc/init.d/conf restore
     It restore's users setting.
     it might restores /etc/inittab, so I'm doing before starting init.
     
  with my case, busybox init works well.
  here is my /sbin/init
/rom/root # cat /sbin/init
#!/bin/sh
if [ -n "$mlddebug" ]; then
  echo run sh begining of /sbin/init
  /bin/sh
fi
[ -x /initrd/init ] && exec /initrd/init $*;
 
PATH=/bin:/sbin:/etc:/usr/bin:/usr/sbin
export PATH
if [ -n "$usbroot" ]; then
  disk=${usbroot%/*}
  mount -n -t devfs none /dev
  mount -n -t proc none /proc
  for i in usbcore ehci-hcd usb-storage usb-ohci; do
        insmod $i
        usleep 500000;
  done

  timeout=5
  [ -n "$usbtimeout" ] && timeout=$usbtimeout;
  while let $(( $timeout > 0 )); do
        echo -n $timeout;
        sleep 1;
        if [ -d /dev/discs/disc$disk  ]; then
                echo found USB disk;
                break;
        fi
        timeout=$(($timeout - 1));
  done
   
  if let $(( $timeout > 0 )) && mount -n -o ro /dev/discs/disc$usbroot /ram; then
    if [ -d  /initrd/root ]; then
      umount /initrd
      freeramdisk /dev/root.old
    fi
    umount /dev
    umount /proc
    pivot_root /ram /ram/initrd
    cd /
    exec /sbin/init $*
  else
     echo Can not mount USB disk:$usbroot;
     umount /dev
     umount /proc
  fi
fi
mount -n -t tmpfs none /ram
cd /
for i in *; do ln -sf /rom/$i /ram; done
mkdir /ram/rom
pivot_root /ram /ram/rom
cd /
mkwritable /proc /tmp /mnt/* /var /var/run
rm -f /dev
mkdir /dev
mount -n -t devfs none /dev
mount -n -t proc none /proc
if [ -d  /rom/initrd/root ]; then
   umount /rom/initrd
   freeramdisk /dev/root.old
fi
/etc/init.d/conf restore
#umount /proc
if [ -n "$mlddebug" ]; then
  echo run sh befoe init
  sh
fi
exec /bin/busybox init $*
/rom/root # 
--------
Hiroshi Ito
Media Lab. Inc.,
URL http://www.mlb.co.jp ( Sorry, Japanese only. )
TEL +81-3-5294-7255  FAX +81-3-5294-7256