path: root/config.d/05diskimage_loopback.defconf

# Hey Emacs, this is a -*- shell-script -*- !!!

# This file provides functions and options to implement loopback
# mounting and access/update of disk images, either via qemu-nbd/nbd
# (for qcow2 images) or via loopback (for raw (or reflink) images).

defconf QEMU_NBD "qemu-nbd" \
	"<cmd>" "qemu-nbd command to run - might be kvm-nbd on some systems"

defconf NBD_DEVICE "/dev/nbd0" \
	"<dev>" "NBD device node to use"

######################################################################

diskimage_mount_loopback ()
{
    local disk="$1"

    local device extra_mount_options

    _setup_image "$disk"

    echo "Mounting disk ${disk}..."
    local m o
    for m in $SYSTEM_DISK_MOUNTS ; do
	local mount_ok=0
	o="${m#*:}" # Offset is after colon
	m="${m%:*}" # Mountpoint is before colon
	echo " mount ${m} from offset ${o}"
	local i
	for i in $(seq 1 5); do
	    mount -o offset=${o}${extra_mount_options} $device "mnt${m}" && {
		mount_ok=1
		break
	    }
	    umount mnt 2>/dev/null || true
	    sleep 1
	done
	[ $mount_ok = 1 ] || die "Failed to mount $disk"
    done

    [ -d "mnt/root" ] || {
	echo "Mounted directory does not look like a root filesystem"
	ls -latr mnt
	exit 1
    }
}

# unmount a qemu image
diskimage_unmount_loopback ()
{
    echo "Unmounting disk"
    sync; sync;

    # umounts are done in reverse.  Be lazy and construct a reverse
    # list, since the shell will handle any strange whitespace for
    # us...  ;-)
    local umounts=""
    local m
    for m in $SYSTEM_DISK_MOUNTS ; do
	umounts="${m%:*}${umounts:+ }${umounts}"
    done
    for m in $umounts ; do
	echo " umount ${m}"
	umount "mnt${m}" || umount "mnt${m}" || true
    done
    _cleanup_image
}

diskimage_mkdir_p_loopback ()
{
    mkdir -p "mnt$1"
}

diskimage_substitute_vars_loopback ()
{
    substitute_vars "$1" "mnt$2"
}

diskimage_chmod_loopback ()
{
    local mode="$1" ; shift
    local i
    for i ; do
        # this should handle wildcards
	eval chmod "$mode" "mnt$i"
    done
}

diskimage_chmod_reference_loopback ()
{
    local ref="$1" ; shift
    local i
    for i ; do
        # this should handle wildcards
	eval chmod --reference="$ref" "mnt$i"
    done
}

diskimage_is_file_loopback ()
{
    [ -f "mnt$1" ]
}

diskimage_is_directory_loopback ()
{
    [ -d "mnt$1" ]
}

diskimage_append_text_file_loopback ()
{
    cat "$1" >> "mnt$2"
}

diskimage_append_text_loopback ()
{
    echo "$1" >> "mnt$2"
}

diskimage_sed_loopback ()
{
    local file="$1" ; shift
    sed -i.org "$@" "mnt$file"
}

diskimage_grep_loopback ()
{
    local file="$1" ; shift
    grep "$@" "mnt$file"
}

diskimage_put_loopback ()
{
    if [ "$1" = "-" ] ; then
	cat >"mnt$2"
    else
	cp "$1" "mnt$2"
    fi
}

diskimage_ln_s_loopback ()
{
    ln -s "$1" "mnt$2"
}

diskimage_command_loopback ()
{
    chroot mnt "$@"
}

diskimage_mv_loopback ()
{
    mv "mnt$1" "mnt$2"
}

diskimage_rm_rf_loopback ()
{
    rm -rf "mnt$1"
}

######################################################################

diskimage_loopback_sanity_check ()
{
    if [ "$SYSTEM_DISK_FORMAT" = "qcow2" -a \
	"$SYSTEM_DISK_ACCESS_METHOD" = "loopback" ] ; then
	check_command $QEMU_NBD
	check_command nbd-client
    fi
}

register_hook post_config_hooks diskimage_loopback_sanity_check

######################################################################

# Private functions

# mount a qemu image via nbd
_connect_nbd() {    
    echo "Connecting nbd to $1"
    mkdir -p mnt
    modprobe nbd
    killall -9 -q $QEMU_NBD || true
    $QEMU_NBD -p 1300 $1 &
    sleep 1
    [ -r $NBD_DEVICE ] || {
	mknod $NBD_DEVICE b 43 0
    }
    umount mnt 2> /dev/null || true
    nbd-client -d $NBD_DEVICE > /dev/null 2>&1 || true
    killall -9 -q nbd-client || true
    nbd-client localhost 1300 $NBD_DEVICE > /dev/null 2>&1 || true &
    sleep 1
}

# disconnect nbd
_disconnect_nbd() {
    echo "Disconnecting nbd"
    sync; sync
    nbd-client -d $NBD_DEVICE > /dev/null 2>&1 || true
    killall -9 -q nbd-client || true
    killall -q $QEMU_NBD || true
}

_setup_image ()
{
    local disk="$1"

    case "$SYSTEM_DISK_FORMAT" in
	qcow2)
	    _connect_nbd "$disk"
	    device=$NBD_DEVICE
	    extra_mount_options=""
	    ;;
	raw|reflink)
	    device="$disk"
	    extra_mount_options=",loop"
	    ;;
	*)
	    die "Error: unknown SYSTEM_DISK_FORMAT=${SYSTEM_DISK_FORMAT}."
    esac
}

_cleanup_image ()
{
    case "$SYSTEM_DISK_FORMAT" in
	qcow2)
	    _disconnect_nbd
	    ;;
	raw|reflink)
	    :
	    ;;
	*)
	    die "Error: unknown SYSTEM_DISK_FORMAT=${SYSTEM_DISK_FORMAT}."
    esac
}