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If target image is a block device, access it directly #22

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merged 2 commits into from
Sep 29, 2023
Merged

If target image is a block device, access it directly #22

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9dc6a9f
Rename $nbd_dev to $disk_dev
Dec 26, 2020
352609f
Add support for block device as target image
Dec 26, 2020
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52 changes: 30 additions & 22 deletions alpine-make-vm-image
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,8 @@
# --partition.
#
# Arguments:
# <image> Path of disk image to use or create if not exists.
# <image> Path of block device or disk image file to use or create
# if it does not exist.
#
# <script> Path of script to execute after installing base system in
# the mounted image and before umounting it.
Expand Down Expand Up @@ -48,10 +49,12 @@
# -P --partition (PARTITION) Create GUID Partition Table (GPT) with a single partition.
# GPT is always created if --boot-mode is UEFI.
#
# -f --image-format IMAGE_FORMAT Format of the disk image (see qemu-img --help).
# -f --image-format IMAGE_FORMAT Format of the disk image (see qemu-img --help). Not
# applicable if the target image is a block device.
#
# -s --image-size IMAGE_SIZE Size of the disk image to create in bytes or with suffix
# (e.g. 1G, 1024M). Default is 2G.
# (e.g. 1G, 1024M). Default is 2G. Not applicable if the
# target image is a block device.
#
# -i --initfs-features INITFS_FEATURES List of additional mkinitfs features (basically modules)
# to be included in initramfs (see mkinitfs -L). "base" and
Expand Down Expand Up @@ -170,12 +173,12 @@ cleanup() {
fi
if [ "$mount_dir" ]; then
umount_recursively "$mount_dir" \
|| die "Failed to unmount $mount_dir; unmount it and disconnect $nbd_dev manually"
|| die "Failed to unmount $mount_dir; unmount it and disconnect $disk_dev manually"
rm -Rf "$mount_dir"
fi
if [ "$nbd_dev" ]; then
qemu-nbd --disconnect "$nbd_dev" \
|| die "Failed to disconnect $nbd_dev; disconnect it manually"
if [ "$disk_dev" ] && ! [ -b "$IMAGE_FILE" ]; then
qemu-nbd --disconnect "$disk_dev" \
|| die "Failed to disconnect $disk_dev; disconnect it manually"
fi
if [ "$INSTALL_HOST_PKGS" = yes ]; then
_apk del $VIRTUAL_PKG
Expand All @@ -190,17 +193,17 @@ _apk() {
attach_image() {
local image="$1"
local format="${2:-}"
local nbd_dev
local disk_dev

nbd_dev=$(get_available_nbd) || {
disk_dev=$(get_available_nbd) || {
modprobe nbd max_part=16
sleep 1
nbd_dev=$(get_available_nbd)
disk_dev=$(get_available_nbd)
} || die 'No available nbd device found!'

qemu-nbd --connect="$nbd_dev" --cache=writeback \
qemu-nbd --connect="$disk_dev" --cache=writeback \
${format:+--format=$format} "$image" \
&& echo "$nbd_dev"
&& echo "$disk_dev"
}

# Prints UUID of filesystem on the specified block device.
Expand All @@ -223,7 +226,7 @@ create_gpt() {
'label: gpt' \
'name=efi,type=U,size=128M,bootable' \
'name=system,type=L' \
| sfdisk "$nbd_dev" ;;
| sfdisk "$disk_dev" ;;
*) die "Invalid mode: $mode" ;;
esac
}
Expand Down Expand Up @@ -505,33 +508,38 @@ if ! command -v "$APK" >/dev/null; then
fi

#-----------------------------------------------------------------------
if [ ! -f "$IMAGE_FILE" ]; then
if [ ! -f "$IMAGE_FILE" ] && [ ! -b "$IMAGE_FILE" ]; then
einfo "Creating $IMAGE_FORMAT image of size $IMAGE_SIZE"
qemu-img create ${IMAGE_FORMAT:+-f $IMAGE_FORMAT} "$IMAGE_FILE" "$IMAGE_SIZE"
fi

#-----------------------------------------------------------------------
einfo "Attaching image $IMAGE_FILE as a NBD device"
if [ -b "$IMAGE_FILE" ]; then
echo "Provided target $IMAGE_FILE is a block device" >&2

nbd_dev=$(attach_image "$IMAGE_FILE" "$IMAGE_FORMAT")
disk_dev="$IMAGE_FILE"
else
einfo "Attaching image $IMAGE_FILE as a NBD device"

disk_dev=$(attach_image "$IMAGE_FILE" "$IMAGE_FORMAT")
fi

#-----------------------------------------------------------------------
if [ "$PARTITION" = yes ] || [ "$BOOT_MODE" = 'UEFI' ]; then
einfo 'Creating GPT partition table'

create_gpt "$nbd_dev" "$BOOT_MODE"
create_gpt "$disk_dev" "$BOOT_MODE"

if [ "$BOOT_MODE" = 'BIOS' ]; then
root_dev="${nbd_dev}p1"
root_dev="${disk_dev}p1"
else
esp_dev="${nbd_dev}p1"
root_dev="${nbd_dev}p2"
esp_dev="${disk_dev}p1"
root_dev="${disk_dev}p2"
fi
# This is needed when running in a container.
settle_dev_node "$root_dev" || die "system didn't create $root_dev node"
else
root_dev="$nbd_dev"
root_dev="$disk_dev"
fi

#-----------------------------------------------------------------------
Expand Down Expand Up @@ -620,7 +628,7 @@ if [ "$BOOT_MODE" = 'BIOS' ]; then
setup_extlinux . "UUID=$root_uuid" "$ROOTFS" "$KERNEL_FLAVOR" "$SERIAL_PORT"

if [ "$PARTITION" = yes ]; then
dd bs=440 count=1 conv=notrunc if=usr/share/syslinux/gptmbr.bin of="$nbd_dev"
dd bs=440 count=1 conv=notrunc if=usr/share/syslinux/gptmbr.bin of="$disk_dev"
sync
fi
fi
Expand Down