#!/bin/sh
# $1 is the kernel version
# this is a really simple way to create an initrd
# if you want to have modules instead of compiling
# support directly into the kernel
# this doesn't deal with software RAID 
# This uses busybox

## Create multiple symbolic links to the same target file
## $1 -- target of each link
## $2+ -- link names
function multilink() {
  local -r TARGET="$1" &&
  local LINK= &&
  shift &&
  for LINK in "$@"; do
    if [[ -n "$LINK" ]]; then
      ln -fnsv "$TARGET" "$LINK"
	fi
  done
}

# initrd parameters

# init command
declare -r INIT_CMD=/sbin/init &&
# where the initrd will be put after "pivot_root"
declare -r OLD_PUT=initrd &&
# console device to use for init
declare -r CONSOLE_DEV=/dev/console &&
# debug initrd?
declare -r DEBUG=off

# make sure we're not wrecking havoc in /initrd
[[ -d "$BUILD_DIRECTORY" ]] &&
cd "$BUILD_DIRECTORY/initrd" &&

# make basic dir structure
mkdir -pv bin dev etc etc.ro lib/modules proc sbin var sys usr/bin mnt initrd tmp &&

# copy config files
cp -av "$INSTALL_ROOT/etc"/{udev,lvm} "$BUILD_DIRECTORY/initrd/etc/" &&

# create dummy passwd, group and fstab
echo "root:x:0:0:root:/root:/bin/sh" > etc/passwd &&
echo "root:x:0:" > etc/group &&
touch etc/fstab &&

# make a read-only copy as well
cp -av etc/* etc.ro/ &&

# copy busybox
cp -av "$INSTALL_ROOT/sbin/busybox" sbin/ &&

# copy device mapper, LVM, and UDEV
cp -av "$INSTALL_ROOT/usr/sbin"/{dmsetup,lvm,udevstart}.static sbin/ &&

# link everything

pushd sbin &&
multilink busybox \
  init \
  insmod \
  halt \
  lsmod \
  makedevs \
  mesg \
  modprobe \
  pivot_root \
  reboot \
  rmmod \
  swapoff \
  swapon \
  &&
multilink udevstart.static \
  udevstart \
  &&
multilink dmsetup.static \
  dmsetup \
  &&
multilink lvm.static \
  vgchange \
  vgdisplay \
  vgscan \
  &&
popd &&

pushd bin &&
multilink ../sbin/busybox \
  '[' \
  ash \
  ls \
  echo \
  mount \
  ln \
  mkdir \
  mknod \
  chown \
  chmod \
  umount \
  tar \
  basename \
  chgrp \
  cat \
  chroot \
  cp \
  cut \
  dd \
  df \
  dirname \
  du \
  env \
  expr \
  false \
  head \
  id \
  install \
  md5sum \
  mv \
  printf \
  pwd \
  realpath \
  rm \
  rmdir \
  sleep \
  sort \
  sync \
  tail \
  tee \
  touch \
  tr \
  true \
  uname \
  uniq \
  who \
  whoami \
  yes \
  which \
  readlink \
  sed \
  dmesg \
  more \
  awk \
  test \
  wc \
  sh \
  &&
popd &&

pushd usr/bin &&
multilink ../../sbin/busybox \
  grep \
  bunzip2 \
  gzip \
  gunzip \
  unzip \
  patch \
  find \
  xargs \
  &&
popd &&

# copy kernel modules
if [[ -d "$INSTALL_ROOT/lib/modules/$1" ]]; then
  cp -av "$INSTALL_ROOT/lib/modules/$1" lib/modules/
fi &&
# copy firmware
if [[ -d "$INSTALL_ROOT/lib/firmware" ]]; then
  cp -av "$INSTALL_ROOT/lib/firmware" lib/
fi &&

# copy console and null nodes
cp -av "$INSTALL_ROOT/dev"/{console,null} dev/ &&

# create linuxrc
cat << EOF > linuxrc &&
#!/bin/sh
# This script is written for Busybox's ash, supposedly it's POSIX compliant now :-).
#
# If you see an error "can't access tty; job control turned off", read this:
# http://www.uclibc.org/FAQ.html#job_control.
#
# Debug: $DEBUG

panic() {
  /bin/echo \$1 &&
  /bin/echo "!!! Dropping into shell, quitting this shell will bring kernel panic..." &&
  exec /bin/sh
}

debug_shell() {
  if ! /bin/[ '$DEBUG' = 'on' ]; then
    return
  fi &&
  /bin/echo "*** \$1. Hit CTRL-D to proceed..." &&
  /bin/sh
}

# somehow this doesn't work with busybox's ash
#export PATH="/bin:/usr/bin:/sbin:/usr/sbin"

debug_shell 'Before filesystems...'

# need this for various diagnostics
/bin/echo "Mounting /proc..."
/bin/mount -nt proc none /proc

# UDEV doesn't support it anywhere else but /sys
/bin/echo "Mounting /sys..."
/bin/mount -nt sysfs none /sys

/bin/echo "Mounting /etc and copying files..."
/bin/mount -nt tmpfs none /etc
/bin/cp -a /etc.ro/* /etc
/bin/ln -s /proc/mounts /etc/mtab

/bin/echo "Mounting /dev..."
/bin/mount -nt ramfs none /dev

/bin/echo "Mounting pts and shm..."
/bin/mkdir -p /dev/pts /dev/shm
/bin/mount -nt devpts none /dev/pts
/bin/mount -nt tmpfs none /dev/shm

/bin/echo "Mounting writeable /tmp and /var..."
/bin/mount -nt tmpfs none /tmp
/bin/mount -nt tmpfs none /var
/bin/mkdir -p /var/lock /var/log

debug_shell 'Before creating device nodes...'

# this is MKNODES on steroids
# this also activates something in the kernel, not sure if it's good
/bin/echo "Creating all available device nodes..."
/sbin/udevstart

# UDEV doesn't create those; it does create /dev/{console,null}
/bin/echo "Creating std* device links..."
/bin/ln -s /proc/self/fd /dev/fd
/bin/ln -s /dev/fd/0 /dev/stdin
/bin/ln -s /dev/fd/1 /dev/stdout
/bin/ln -s /dev/fd/2 /dev/stderr

/bin/echo "Invoking disk mapper and LVM..."
/sbin/dmsetup mknodes
/sbin/vgscan   --ignorelockingfailure --mknodes
/sbin/vgchange --ignorelockingfailure -a y

# ========================================================================== #
# This is where you can add code to load modules for devices and filesystems #
# ========================================================================== #
# /sbin/modprobe xxx

# ============================================================== #
# Don't edit past here unless you really know what you are doing #
# ============================================================== #

debug_shell 'Before real root...'

# do we have real_root?
if ! /bin/cat /proc/cmdline | /usr/bin/grep -q 'real_root=[^[:space:]]\\+'; then
  panic '!!! VARIABLE real_root NOT SPECIFIED'
fi

# extract real_root device name; must not have whitespace in the name
#ROOT_DEV=\$(/bin/cat /proc/cmdline | /bin/sed -e 's|^.*real_root=\\(\\S\\+\\)\\(\\s.*\\)\\?$|\1|g')
ROOT_DEV=\$(/bin/cat /proc/cmdline)
ROOT_DEV=\${ROOT_DEV##*real_root=}
# the brackets below must have a SPACE and a TAB
ROOT_DEV=\${ROOT_DEV%%[ 	]*}
/bin/echo "Mounting real root: \$ROOT_DEV..."
/bin/echo "0x100" > /proc/sys/kernel/real-root-dev
# kernel must know this filesystem; it'd be nice to do a pre-test here
/bin/mount -n \$ROOT_DEV /mnt

if ! /bin/test -x "/mnt$INIT_CMD"; then
  panic "!!! REAL ROOT MOUNTED BUT HAS NO INIT: $INIT_CMD"
fi

# if this directory doesn't exist, pivot_root fails
/bin/echo "Checking for $OLD_PUT directory on real root..."
/bin/mkdir -p /mnt/$OLD_PUT

# make sure the /dev/console device node exists in the new root
/bin/echo "Checking for $CONSOLE_DEV device node on real root..."
if ! /bin/test -c "/mnt$CONSOLE_DEV"; then
  /bin/cp -a $CONSOLE_DEV /mnt$CONSOLE_DEV
fi

# BASH only: last precaution
# we need that many backslahes here before the single backquote
#read -n 3 -p "Type \\\`yes' now to drop into shell (16 seconds): " -t 16 PAUSE && (
#  if [[ "\$PAUSE" == 'yes' ]]; then
#    /bin/echo "*** Press CTRL-D to exit and continue..."
#    /bin/sh
#  fi
#)

/bin/echo "Umounting filesystems..."
/bin/umount -n /tmp
/bin/umount -n /var
/bin/umount -n /dev/pts
/bin/umount -n /dev/shm
/bin/umount -n /sys
/bin/umount -n /proc
# those two should go last to minimize ocurrence of "/etc/mtab not found" error
/bin/umount -n /dev
/bin/umount -n /etc

debug_shell 'Before pivot_root...'

/bin/echo "Doing pivot root; initrd root: /$OLD_PUT"
cd /mnt
if ! /sbin/pivot_root . $OLD_PUT; then
  panic "!!! THE PIVOT-ROOT COMMAND FAILED"
fi

### WE ARE IN THE NEW ROOT NOW; OUR OLD FILESYSTEM IS IN /$OLD_PUT

# this \`cd' is just cosmetic, so that \`pwd' command produces correct output
cd /

debug_shell 'Before init...'

/bin/echo "Starting init: $INIT_CMD \$@"
exec /bin/chroot . $INIT_CMD \$@ < $CONSOLE_DEV > $CONSOLE_DEV 2>&1
EOF

chmod +x linuxrc