BusyBox のダウンロード

# wget http://busybox.net/downloads/busybox-1.15.3.tar.bz2

展開

# tar xvjf busybox-1.15.3.tar.bz2
# cd busybox-1.15.3

設定

# make menuconfig
    Busybox Setting --->
        Build Options --->
            [*] Build BusyBox as a static binary (no shared libs)

コンパイル

# make

インストール

通常ならカレントディレクトリの_installにインストールされる。

# sudo make install

initramfsの作成

coLinuxの簡易インストーラーとしてinitramfsを作成する。

# cd _install
# sudo rm linuxrc
# sudo mkdir -p proc sys dev mnt tmp etc/init.d root var/run var/lock var/tmp
# sudo chmod 1777 tmp
# sudo chmod 1777 var/tmp
# sudo sh -c 'echo none /proc proc defaults 0 0 > etc/fstab'
# sudo sh -c 'echo none /sys sysfs defaults 0 0 >> etc/fstab'
# sudo sh -c 'echo nameserver 8.8.8.8 > etc/resolv.conf'
# sudo sh -c 'echo nameserver 8.8.4.4 >> etc/resolv.conf'
# sudo sh -c 'echo 127.0.0.1 localhost > etc/hosts'
# sudo sh -c 'echo busybox > etc/hostname'
# sudo sh -c 'echo root:*:0:0:root:/:/bin/sh > etc/passwd'
# sudo sh -c 'echo root:x:0: > etc/group'
# sudo sh -c 'echo localhost 127.0.0.0 > etc/networks'
# sudo sh -c 'echo localnet1 192.168.0.0 >> etc/networks'
# sudo sh -c 'echo localnet2 10.0.0.0 >> etc/networks'
# sudo sh -c 'printf "order hosts, bind\nmulti on\n" > etc/host.conf'
# sudo cp -a /usr/share/zoneinfo/Asia/Tokyo etc/localtime
# sudoedit etc/nsswitch.conf

passwd: files
shadow: files
group: files

hosts: files dns
networks: files

protocols: files
services: files
ethers: files
rpc: files

# sudo touch init
# sudo chmod +x init
# sudoedit init

#!/bin/sh

export PATH="/bin:/sbin:/usr/bin:/usr/sbin"

exec /sbin/init

# sudoedit etc/inittab

::sysinit:/etc/init.d/rcS
::askfirst:-/bin/sh
::restart:/sbin/init
::ctrlaltdel:/sbin/reboot
::shutdown:/bin/umount -a -r
::shutdown:/sbin/swapoff -a

# sudo touch etc/init.d/rcS
# sudo chmod +x etc/init.d/rcS
# sudoedit etc/init.d/rcS

#!/bin/sh

/bin/mount -a

/sbin/mdev -s
echo "/sbin/mdev" > /proc/sys/kernel/hotplug

/bin/hostname -F /etc/hostname

/sbin/ifconfig lo 127.0.0.1
/sbin/udhcpc

# sudo mkdir -p usr/share/udhcpc
# sudo touch usr/share/udhcpc/default.script
# sudo chmod +x usr/share/udhcpc/default.script
# sudoedit usr/share/udhcpc/default.script

#!/bin/sh

RESOLV_CONF="/etc/resolv.conf"

[ -n "$1" ] || { echo "Error: should be called from udhcpc"; exit 1; }

NETMASK=""
[ -n "$subnet" ] && NETMASK="netmask $subnet"
BROADCAST="broadcast +"
[ -n "$broadcast" ] && BROADCAST="broadcast $broadcast"

case "$1" in
  deconfig)
    ifconfig $interface 0.0.0.0
    ;;
  renew|bound)
    ifconfig $interface $ip $NETMASK $BROADCAST
    if [ -n "$router" ] ; then
      while route del default gw 0.0.0.0 dev $interface ; do
        :
      done

      metric=0
      for i in $router ; do
        route add default gw $i dev $interface metric $((metric++))
      done
    fi
    echo -n > $RESOLV_CONF-$$
    [ -n "$domain" ] && echo "search $domain" >> $RESOLV_CONF-$$
    for i in $dns ; do
      echo " Adding DNS server $i"
      echo "nameserver $i" >> $RESOLV_CONF-$$
    done
    mv $RESOLV_CONF-$$ $RESOLV_CONF
    ;;
esac

exit 0

ついでにdebootstrapも入れておく。

# cd
# wget http://archive.ubuntu.com/ubuntu/pool/main/d/debootstrap/debootstrap_1.0.20.tar.gz
# tar -xvzf debootstrap_1.0.20.tar.gz
# cd debootstrap
# sudo make install DESTDIR=~/busybox-1.15.3/_install

cpio + gzip で固める

# find . | cpio --quiet -o -H newc | gzip -9 > ../../initrd.img

参考リンク

BusyBox