/usr/share/initramfs-tools/scripts/image

image

# -*- shell-script -*-

image_mount_storage()
{
    local mnt="$1"

    local_top
    local_device_setup "${ROOT}" "usb storage"
    ROOT="${DEV}"

    # Default delay is around 10s
    delay=${ROOTDELAY:-10}

    retry_count=0
    # loop until usb storage found
    while [ ${retry_count} -lt ${delay} ] && [ ! -e ${ROOT} ] ; do
        [ "$quiet" != "y" ] && log_begin_msg "Wait ${ROOT} found"
        /bin/sleep 1
        retry_count=$(( ${retry_count} + 1 ))
        [ "$quiet" != "y" ] && log_end_msg
    done

    # Get the root filesystem type if not set
    if [ -z "${ROOTFSTYPE}" ]; then
        FSTYPE=$(get_fstype "${ROOT}")
    else
        FSTYPE=${ROOTFSTYPE}
    fi

    local_premount

    if [ "${readonly}" = "y" ]; then
        roflag=-r
    else
        roflag=-w
    fi

    # FIXME This has no error checking
    modprobe ${FSTYPE}

    checkfs ${ROOT} ${mnt} "${FSTYPE}"

    # FIXME This has no error checking
    # Mount root
    if [ "${FSTYPE}" != "unknown" ]; then
        mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${mnt}
    else
        mount ${roflag} ${ROOTFLAGS} ${ROOT} ${mnt}
    fi
}

image_mount_root()
{
    local mnt="/boot"
    local image="rootfs.cpio.gz"
    local tmpfs=

    for x in $(cat /proc/cmdline); do
        case ${x} in
        image=*)
            image=${x#image=}
            ;;
        tmpfs=*)
            tmpfs=${x#tmpfs=}
            ;;
        esac
    done

    modprobe usb_storage

    wait_for_udev 10

    [ "$quiet" != "y" ] && log_begin_msg "Creating tmpfs ${tmpfs}"
    if [ -z "${tmpfs}" ]; then
        mount -t tmpfs tmpfs ${rootmnt}
    else
        mount -t tmpfs -o size=${tmpfs} tmpfs ${rootmnt}
    fi
    [ "$quiet" != "y" ] && log_end_msg

    if [ ! -e ${mnt} ]; then
        mkdir ${mnt}
    fi

    image_mount_storage ${mnt}

    [ "$quiet" != "y" ] && log_begin_msg "Extracting ${image}"
    cd ${rootmnt} && zcat ${mnt}/${image} | cpio -idm
    [ "$quiet" != "y" ] && log_end_msg

    umount ${mnt}
}

mountroot()
{
    image_mount_root
}

mount_top()
{
    :
}

mount_premount()
{
    :
}

mount_bottom()
{
    :
}

Example of GRUB entry

menuentry 'Debian GNU/Linux (USB Boot)' {
  load_video
  insmod gzio
  insmod ext2
  echo 'Loading vmlinuz ...'
  linux /vmlinuz root=LABEL=USB_BOOT ro boot=image image=rootfs.cpio.gz tmpfs=8192M
  echo 'Loading initrd ...'
  initrd /initrd.img
}