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|
#!/bin/sh
# Enable strict shell mode
set -euo pipefail
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MOUNT="/bin/mount"
UMOUNT="/bin/umount"
INIT="/sbin/init"
ROOT_MOUNT="/mnt"
ROOT_RODEVICE=""
ROOT_RWDEVICE=""
ROOT_ROMOUNT="/media/rfs/ro"
ROOT_RWMOUNT="/media/rfs/rw"
ROOT_RWRESET="no"
# Copied from initramfs-framework. The core of this script probably should be
# turned into initramfs-framework modules to reduce duplication.
udev_daemon() {
OPTIONS="/sbin/udev/udevd /sbin/udevd /lib/udev/udevd /lib/systemd/systemd-udevd"
for o in $OPTIONS; do
if [ -x "$o" ]; then
echo $o
return 0
fi
done
return 1
}
_UDEV_DAEMON=`udev_daemon`
early_setup() {
mkdir -p /proc
mkdir -p /sys
$MOUNT -t proc proc /proc
$MOUNT -t sysfs sysfs /sys
$MOUNT -t devtmpfs none /dev
mkdir -p /run
mkdir -p /var/run
$_UDEV_DAEMON --daemon
udevadm trigger --action=add
}
read_args() {
[ -z "${CMDLINE+x}" ] && CMDLINE=`cat /proc/cmdline`
for arg in $CMDLINE; do
optarg=`expr "x$arg" : 'x[^=]*=\(.*\)'`
case $arg in
root=*)
ROOT_RODEVICE=$optarg ;;
rootfstype=*)
modprobe $optarg 2> /dev/null ;;
rootrw=*)
ROOT_RWDEVICE=$optarg ;;
rootrwfstype=*)
modprobe $optarg 2> /dev/null ;;
rootrwreset=*)
ROOT_RWRESET=$optarg ;;
video=*)
video_mode=$arg ;;
vga=*)
vga_mode=$arg ;;
init=*)
INIT=$optarg ;;
console=*)
if [ -z "${console_params+x}" ]; then
console_params=$arg
else
console_params="$console_params $arg"
fi ;;
esac
done
}
fatal() {
echo $1 >$CONSOLE
echo >$CONSOLE
exec sh
}
early_setup
[ -z "${CONSOLE+x}" ] && CONSOLE="/dev/console"
read_args
mount_and_boot() {
mkdir -p $ROOT_MOUNT $ROOT_ROMOUNT $ROOT_RWMOUNT
# Build mount options for read only root filesystem.
# If no read-only device was specified via kernel commandline, use current
# rootfs.
if [ -z "${ROOT_RODEVICE}" ]; then
ROOT_ROMOUNTOPTIONS="--bind,ro /"
else
ROOT_ROMOUNTOPTIONS="-o ro,noatime,nodiratime $ROOT_RODEVICE"
fi
# Mount rootfs as read-only to mount-point
if ! $MOUNT $ROOT_ROMOUNTOPTIONS $ROOT_ROMOUNT ; then
fatal "Could not mount read-only rootfs"
fi
# Build mount options for read write root filesystem.
# If no read-write device was specified via kernel commandline, use tmpfs.
if [ -z "${ROOT_RWDEVICE}" ]; then
ROOT_RWMOUNTOPTIONS="-t tmpfs -o rw,noatime,mode=755 tmpfs"
else
ROOT_RWMOUNTOPTIONS="-o rw,noatime,mode=755 $ROOT_RWDEVICE"
fi
# Mount read-write filesystem into initram rootfs
if ! $MOUNT $ROOT_RWMOUNTOPTIONS $ROOT_RWMOUNT ; then
fatal "Could not mount read-write rootfs"
fi
# Reset read-write filesystem if specified
if [ "yes" == "$ROOT_RWRESET" -a -n "${ROOT_RWMOUNT}" ]; then
rm -rf $ROOT_RWMOUNT/*
fi
# Determine which unification filesystem to use
union_fs_type=""
if grep -w "overlay" /proc/filesystems; then
union_fs_type="overlay"
elif grep -w "aufs" /proc/filesystems; then
union_fs_type="aufs"
else
union_fs_type=""
fi
# Create/Mount overlay root filesystem
case $union_fs_type in
"overlay")
mkdir -p $ROOT_RWMOUNT/upperdir $ROOT_RWMOUNT/work
$MOUNT -t overlay overlay -o "lowerdir=$ROOT_ROMOUNT,upperdir=$ROOT_RWMOUNT/upperdir,workdir=$ROOT_RWMOUNT/work" $ROOT_MOUNT
;;
"aufs")
$MOUNT -t aufs -o "dirs=$ROOT_RWMOUNT=rw:$ROOT_ROMOUNT=ro" aufs $ROOT_MOUNT
;;
"")
fatal "No overlay filesystem type available"
;;
esac
# Move read-only and read-write root filesystem into the overlay filesystem
mkdir -p $ROOT_MOUNT/$ROOT_ROMOUNT $ROOT_MOUNT/$ROOT_RWMOUNT
$MOUNT -n --move $ROOT_ROMOUNT ${ROOT_MOUNT}/$ROOT_ROMOUNT
$MOUNT -n --move $ROOT_RWMOUNT ${ROOT_MOUNT}/$ROOT_RWMOUNT
# Watches the udev event queue, and exits if all current events are handled
udevadm settle --timeout=3
# Kills the current udev running processes, which survived after
# device node creation events were handled, to avoid unexpected behavior
killall -9 "${_UDEV_DAEMON##*/}" 2>/dev/null
# Remove /run /var/run that are created in early_setup
rm -rf /run /var/run
# Move the mount points of some filesystems over to
# the corresponding directories under the real root filesystem.
for dir in `awk '/\/dev.* \/run\/media/{print $2}' /proc/mounts`; do
mkdir -p ${ROOT_MOUNT}/media/${dir##*/}
$MOUNT -n --move $dir ${ROOT_MOUNT}/media/${dir##*/}
done
$MOUNT -n --move /proc ${ROOT_MOUNT}/proc
$MOUNT -n --move /sys ${ROOT_MOUNT}/sys
$MOUNT -n --move /dev ${ROOT_MOUNT}/dev
cd $ROOT_MOUNT
# busybox switch_root supports -c option
exec chroot $ROOT_MOUNT $INIT ||
fatal "Couldn't chroot, dropping to shell"
}
mount_and_boot
|
