#!/bin/sh
 
 PATH=/bin:/usr/bin:/sbin:/usr/sbin
 export PATH
 
 problem()
 {
    printf "Encountered a problem!\n\nDropping you to a shell.\n\n"
    sh
 }
 
 no_device()
 {
    printf "The device %s, which is supposed to contain the\n" $1
    printf "root file system, does not exist.\n"
    printf "Please fix this problem and exit this shell.\n\n"
 }
 
 no_mount()
 {
    printf "Could not mount device %s\n" $1
    printf "Sleeping forever. Please reboot and fix the kernel command line.\n\n"
    printf "Maybe the device is formatted with an unsupported file system?\n\n"
    printf "Or maybe filesystem type autodetection went wrong, in which case\n"
    printf "you should add the rootfstype=... parameter to the kernel command line.\n\n"
    printf "Available partitions:\n"
 }
 
 do_mount_root()
 {
    mkdir /.root
    [ -n "$rootflags" ] && rootflags="$rootflags,"
    rootflags="$rootflags$ro"
 
    case "$root" in
       /dev/* ) device=$root ;;
       UUID=* ) eval $root; device="/dev/disk/by-uuid/$UUID"  ;;
       LABEL=*) eval $root; device="/dev/disk/by-label/$LABEL" ;;
       ""     ) echo "No root device specified." ; problem    ;;
    esac
 
    while [ ! -b "$device" ] ; do
        no_device $device
        problem
    done
 
    if ! mount -n -t "$rootfstype" -o "$rootflags" "$device" /.root ; then
        no_mount $device
        cat /proc/partitions
        while true ; do sleep 10000 ; done
    else
        echo "Successfully mounted device $root"
    fi
 }
 
 init=/sbin/init
 root=
 rootdelay=
 rootfstype=auto
 ro="ro"
 rootflags=
 device=
 
 mount -n -t devtmpfs devtmpfs /dev
 mount -n -t proc     proc     /proc
 mount -n -t sysfs    sysfs    /sys
 mount -n -t tmpfs    tmpfs    /run
 
 read -r cmdline < /proc/cmdline
 
 for param in $cmdline ; do
   case $param in
     init=*      ) init=${param#init=}             ;;
     root=*      ) root=${param#root=}             ;;
     rootdelay=* ) rootdelay=${param#rootdelay=}   ;;
     rootfstype=*) rootfstype=${param#rootfstype=} ;;
     rootflags=* ) rootflags=${param#rootflags=}   ;;
     ro          ) ro="ro"                         ;;
     rw          ) ro="rw"                         ;;
   esac
 done
 
 # udevd location depends on version
 if [ -x /sbin/udevd ]; then
   UDEVD=/sbin/udevd
 elif [ -x /lib/udev/udevd ]; then
   UDEVD=/lib/udev/udevd
 elif [ -x /lib/systemd/systemd-udevd ]; then
   UDEVD=/lib/systemd/systemd-udevd
 else
   echo "Cannot find udevd nor systemd-udevd"
   problem
 fi
 
 ${UDEVD} --daemon --resolve-names=never
 udevadm trigger
 udevadm settle
 
 if [ -f /etc/mdadm.conf ] ; then mdadm -As                       ; fi
 if [ -x /sbin/vgchange  ] ; then /sbin/vgchange -a y > /dev/null ; fi
 if [ -n "$rootdelay"    ] ; then sleep "$rootdelay"              ; fi
 
 do_mount_root
 
 killall -w ${UDEVD##*/}
 
 exec switch_root /.root "$init" "$@"