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Filename : update-initramfs
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#!/bin/sh

STATEDIR=/var/lib/initramfs-tools
BOOTDIR=/boot
CONF=/etc/initramfs-tools/update-initramfs.conf
USETRIGGERS=true
mode=""
version=""
update_initramfs=yes
backup_initramfs=no

set -e

[ -r ${CONF} ] && . ${CONF}

case "$DPKG_MAINTSCRIPT_PACKAGE" in
linux-image-*)
	if [ -z "$INITRAMFS_TOOLS_KERNEL_HOOK" ]; then
		# kernel maintainer script called us directly; ignore
		# it and let the hook script handle it instead
		echo "update-initramfs: deferring update (hook will be called later)"
		exit 0
	fi
	;;
?*)
	if	   $USETRIGGERS						\
		&& [ $# = 1 ]						\
		&& [ x"$1" = x-u ]					\
		&& dpkg-trigger --check-supported 2>/dev/null
	then
		if dpkg-trigger --no-await update-initramfs; then
			echo "update-initramfs: deferring update (trigger activated)"
			exit 0
		fi
	fi
	;;
esac

usage()
{
	if [ -n "${1:-}" ]; then
		printf "${*}\n\n" >&2
	fi
	cat >&2 << EOF
Usage: ${0} [OPTION]...

Options:
 -k version	Specify kernel version or 'all'
 -c		Create a new initramfs
 -u		Update an existing initramfs
 -d		Remove an existing initramfs
 -t		Take over a custom initramfs with this one
 -b directory	Set alternate boot directory
 -v		Be verbose
 -h		This message

EOF
	exit 1
}

# chroot check
chrooted()
{
	# borrowed from udev's postinst
	if [ "$(stat -c %d/%i /)" = "$(stat -Lc %d/%i /proc/1/root 2>/dev/null)" ]; then
		# the devicenumber/inode pair of / is the same as that of
		# /sbin/init's root, so we're *not* in a chroot and hence
		# return false.
		return 1
	fi
return 0
}

mild_panic()
{
	if [ -n "${1:-}" ]; then
		printf "${*}\n" >&2
	fi
	exit 0
}

panic()
{
	if [ -n "${1:-}" ]; then
		printf "${*}\n" >&2
	fi
	exit 1
}

verbose()
{
	if [ "${verbose}" = 1 ]; then
		printf "${*}\n"
	fi
}

version_exists()
{
	[ -e "${STATEDIR}/${1}" ] && [ -e "${initramfs}" ]
	return $?
}

set_initramfs()
{
	initramfs="${BOOTDIR}/initrd.img-${version}"
}


# backup initramfs while running
backup_initramfs()
{
	[ ! -r "${initramfs}" ] && return 0
	initramfs_bak="${initramfs}.dpkg-bak"
	[ -r "${initramfs_bak}" ] && rm -f "${initramfs_bak}"
	ln -f "${initramfs}" "${initramfs_bak}" \
		|| cp -a "${initramfs}" "${initramfs_bak}"
	verbose "Keeping ${initramfs_bak}"
}

# keep booted initramfs
backup_booted_initramfs()
{
	initramfs_bak="${initramfs}.dpkg-bak"

	# first time run thus no backup
	[ ! -r "${initramfs_bak}" ] && return 0

	# chroot with no /proc
	[ ! -r /proc/uptime ] && rm -f "${initramfs_bak}" && return 0

	# no kept backup wanted
	[ "${backup_initramfs}" = "no" ] && rm -f "${initramfs_bak}" && return 0

	# no backup yet
	if [ ! -r "${initramfs}.bak" ]; then
		mv -f ${initramfs_bak} "${initramfs}.bak"
		verbose "Backup ${initramfs}.bak"
		return 0
	fi

	# keep booted initramfs
	boot_initramfs=
	uptime_days=$(awk '{printf "%d", $1 / 3600 / 24}' /proc/uptime)
	if [ -n "$uptime_days" ]; then
		boot_initramfs=$(find "${initramfs}.bak" -mtime +${uptime_days})
	fi
	if [ -n "${boot_initramfs}" ]; then
		mv -f "${initramfs_bak}" "${initramfs}.bak"
		verbose "Backup ${initramfs}.bak"
		return 0
	fi
	verbose "Removing current backup ${initramfs_bak}"
	rm -f ${initramfs_bak}
}

# nuke generated copy
remove_initramfs_bak()
{
	[ -z "${initramfs_bak:-}" ] && return 0
	rm -f "${initramfs_bak}"
	verbose "Removing ${initramfs_bak}"
}


generate_initramfs()
{
	echo "update-initramfs: Generating ${initramfs}"
	OPTS="-o"
	if [ "${verbose}" = 1 ]; then
		OPTS="-v ${OPTS}"
	fi
	if mkinitramfs ${OPTS} "${initramfs}.new" "${version}"; then
		mv -f "${initramfs}.new" "${initramfs}"
		set_sha1
		# Guard against an unclean shutdown
		sync -f "${initramfs}"
	else
		mkinitramfs_return="$?"
		remove_initramfs_bak
		rm -f "${initramfs}.new"
		echo "update-initramfs: failed for ${initramfs} with $mkinitramfs_return." >&2
		exit $mkinitramfs_return
	fi
}

# Invoke bootloader
run_bootloader()
{
	# invoke policy conformant bootloader hooks
	if [ -d /etc/initramfs/post-update.d/ ]; then
		run-parts --arg=${version} --arg=${initramfs} \
			/etc/initramfs/post-update.d/
		return 0
	fi
}

compare_sha1()
{
	sha1sum "${initramfs}" | diff "${STATEDIR}/${version}" - >/dev/null 2>&1
	return $?
}

# Note that this must overwrite so that updates work.
set_sha1()
{
	sha1sum "${initramfs}" > "${STATEDIR}/${version}"
}

delete_sha1()
{
	rm -f "${STATEDIR}/${version}"
}

# ro /boot is not modified
ro_boot_check()
{
	# check irrelevant inside of a chroot
	if [ ! -r /proc/mounts ] || chrooted; then
		return 0
	fi

	boot_opts=$(awk '/boot/{if ((match($4, /^ro/) || match($4, /,ro/)) \
		&& $2 == "/boot") print "ro"}' /proc/mounts)
	if [ -n "${boot_opts}" ]; then
		echo "WARNING: /boot is ro mounted."
		echo "update-initramfs: Not updating ${initramfs}"
		exit 0
	fi
}

get_sorted_versions()
{
	version_list="$(ls -1 "${STATEDIR}" | linux-version sort --reverse)"

	verbose "Available versions: ${version_list}"
}

set_current_version()
{
	if [ -f /boot/initrd.img-`uname -r` ]; then
		version=`uname -r`
	fi
}

set_linked_version()
{
	linktarget=
	if [ -e /initrd.img ] && [ -L /initrd.img ]; then
		linktarget="$(basename "$(readlink /initrd.img)")"
	fi

	if [ -e /boot/initrd.img ] && [ -L /boot/initrd.img ]; then
		linktarget="$(basename "$(readlink /boot/initrd.img)")"
	fi

	if [ -z "${linktarget}" ]; then
		return
	fi

	version="${linktarget##initrd.img-}"
}

set_highest_version()
{
	get_sorted_versions
	if [ -z "${version_list}" ]; then
		version=
		return
	fi
	set -- ${version_list}
	version=${1}
}

create()
{
	if [ -z "${version}" ]; then
		usage "Create mode requires a version argument"
	fi

	set_initramfs

	if [ "${takeover}" = 0 ]; then
		if version_exists "${version}"; then
			panic "Cannot create version ${version}: already exists"
		fi

		if [ -e "${initramfs}" ]; then
			panic "${initramfs} already exists, cannot create."
		fi
	fi

	generate_initramfs

	run_bootloader
}

update()
{
	if [ "${update_initramfs}" = "no" ]; then
		echo "update-initramfs: Not updating initramfs."
		exit 0
	fi

	if [ -z "${version}" ]; then
		set_highest_version
	fi

	if [ -z "${version}" ]; then
		set_linked_version
	fi

	if [ -z "${version}" ]; then
		set_current_version
	fi

	if [ -z "${version}" ]; then
		verbose "Nothing to do, exiting."
		exit 0
	fi

	set_initramfs

	ro_boot_check

	altered_check

	backup_initramfs

	generate_initramfs

	run_bootloader

	backup_booted_initramfs
}

delete()
{
	if [ -z "${version}" ]; then
		usage "Delete mode requires a version argument"
	fi

	set_initramfs

	if [ "${takeover}" = 0 ]; then
		if [ ! -e "${initramfs}" ]; then
			panic "Cannot delete ${initramfs}, doesn't exist."
		fi

		if ! version_exists "${version}"; then
			panic "Cannot delete version ${version}: Not created by this utility."
		fi
	fi

	altered_check

	echo "update-initramfs: Deleting ${initramfs}"

	delete_sha1

	rm -f "${initramfs}" "${initramfs}.bak"
}

# Check for update mode on existing and modified initramfs
altered_check()
{
	# No check on takeover
	[ "${takeover}" = 1 ] && return 0
	if [ ! -e "${initramfs}" ]; then
		mild_panic "${initramfs} does not exist. Cannot update."
	fi
	if ! compare_sha1; then
		echo "update-initramfs: ${initramfs} has been altered." >&2
		mild_panic "update-initramfs: Cannot update. Override with -t option."
	fi
}

# Defaults
verbose=0
yes=0
# We default to takeover=1 in Ubuntu, but not Debian
takeover=1

##

while getopts "k:cudyvtb:h?" flag; do
	case "${flag}" in
	k)
		version="${OPTARG}"
		;;
	c)
		mode="c"
		;;
	d)
		mode="d"
		;;
	u)
		mode="u"
		;;
	v)
		verbose="1"
		;;
	y)
		yes="1"
		;;
	t)
		takeover="1"
		;;
	b)
		BOOTDIR="${OPTARG}"
		if [ ! -d "${BOOTDIR}" ]; then
			echo "Error: ${BOOTDIR} is not a directory." >&2
			exit 1
		fi
		;;
	h|?)
		usage
		;;
	esac
done

shift $((${OPTIND} - 1))

if [ $# -ne 0 ]; then
	printf "Extra argument '%s'\n\n" "$1" >&2
	usage
fi

# Validate arguments
if [ -z "${mode}" ]; then
	usage "You must specify at least one of -c, -u, or -d."
fi

if [ "${version}" = "all" ] \
	|| ( [ "${update_initramfs}" = "all" ] && [ -z "${version}" ] ); then
	: FIXME check for --yes, and if not ask are you sure
	get_sorted_versions
	if [ -z "${version_list}" ]; then
		verbose "Nothing to do, exiting."
		exit 0
	fi

	OPTS="-b ${BOOTDIR}"
	if [ "${verbose}" = "1" ]; then
		OPTS="${OPTS} -v"
	fi
	if [ "${takeover}" = "1" ]; then
		OPTS="${OPTS} -t"
	fi
	if [ "${yes}" = "1" ]; then
		OPTS="${OPTS} -y"
	fi
	for u_version in ${version_list}; do
		verbose "Execute: ${0} -${mode} -k \"${u_version}\" ${OPTS}"
		"${0}" -${mode} -k "${u_version}" ${OPTS}
	done
	exit 0
fi


case "${mode}" in
	c)
		create
		;;
	d)
		delete
		;;
	u)
		update
		;;
esac