mkimage.sh.in: add comments

This commit is contained in:
Michael Aldridge 2017-08-13 01:40:19 -07:00
parent 7a7766cfcb
commit 2724ae0abb
1 changed files with 73 additions and 4 deletions

View File

@ -36,6 +36,10 @@ trap 'printf "\nInterrupted! exiting...\n"; cleanup; exit 0' INT TERM HUP
# shellcheck source=./lib.sh
. ./lib.sh
# This script has a special cleanup() function since it needs to
# unmount the rootfs as mounted on a loop device. This function is
# defined after sourcing the library functions to ensure it is the
# last one defined.
cleanup() {
unmount_pseudofs
umount -f "${ROOTFS}/boot" 2>/dev/null
@ -48,6 +52,12 @@ cleanup() {
[ -d "$ROOTFS" ] && rmdir "$ROOTFS"
}
# This script is designed to take in a complete platformfs and spit
# out an image that is suitable for writing with dd. The image is
# configurable in terms of the filesystem layout, but not in terms of
# the installed system itself. Customization to the installed system
# should be made during the mkplatformfs step.
usage() {
cat <<_EOF
Usage: $PROGNAME [options] <rootfs-tarball>
@ -99,7 +109,7 @@ elif [ ! -r "$ROOTFS_TARBALL" ]; then
fi
# By default we build all platform images with a 64MiB boot partition
# formated FAT16, and an approxomately 1.9GiB root partition formated
# formated FAT16, and an approximately 1.9GiB root partition formated
# ext4. More exotic combinations are of course possible, but this
# combination works on all known platforms.
: "${IMGSIZE:=2G}"
@ -116,7 +126,7 @@ check_tools
PLATFORM="${ROOTFS_TARBALL#void-}"
PLATFORM="${PLATFORM%-ROOTFS*}"
# This is an aweful hack since the script isn't using privesc
# This is an awful hack since the script isn't using privesc
# mechanisms selectively. This is a TODO item.
if [ "$(id -u)" -ne 0 ]; then
die "need root perms to continue, exiting."
@ -144,14 +154,18 @@ truncate -s "${IMGSIZE}" "$FILENAME" >/dev/null 2>&1
# because otherwise things will go very badly for the host system.
ROOTFS=$(mktemp -d) || die "Could not create tmpdir for ROOTFS"
info_msg "Creating disk image partitions/filesystems ..."
if [ "$BOOT_FSTYPE" = "vfat" ]; then
# The mkfs.vfat program tries to make some "intelligent" choices
# about the type of filesystem it creates. Instead we set options
# if the type is vfat to ensure that the same options will be used
# every time.
_args="-I -F16"
fi
case "$PLATFORM" in
cubieboard2|cubietruck|ci20*|odroid-c2*)
# These platforms use a single partition for the entire filesystem.
sfdisk "${FILENAME}" <<_EOF
label: dos
2048,,L
@ -162,6 +176,10 @@ _EOF
ROOT_UUID=$(blkid -o value -s UUID "${LOOPDEV}p1")
;;
*)
# These platforms use a partition layout with a small boot
# partition (64M by default) and the rest of the space as the
# root filesystem. This is the generally preferred disk
# layout for new platforms.
sfdisk "${FILENAME}" <<_EOF
label: dos
2048,${BOOT_FSSIZE},b,*
@ -173,6 +191,13 @@ _EOF
# shellcheck disable=SC2086
mkfs.${BOOT_FSTYPE} $_args "${LOOPDEV}p1" >/dev/null
case "$ROOT_FSTYPE" in
# Because the images produced by this script are generally
# either on single board computers using flash memory or
# in cloud environments that already provide disk
# durability, we shut off the journal for ext filesystems.
# For flash memory this greatly extends the life of the
# memory and for cloud images this lowers the overhead by
# a small amount.
ext[34]) disable_journal="-O ^has_journal";;
esac
mkfs.${ROOT_FSTYPE} "$disable_journal" "${LOOPDEV}p2" >/dev/null 2>&1
@ -184,25 +209,50 @@ _EOF
;;
esac
# This step unpacks the platformfs tarball made by mkplatformfs.sh.
info_msg "Unpacking rootfs tarball ..."
if [ "$PLATFORM" = "beaglebone" ]; then
# The beaglebone requires some special extra handling. The MLO
# program is a special first stage boot loader that brings up
# enough of the processor to then load u-boot which loads the rest
# of the system. The noauto option also prevents /boot from being
# mounted during system startup.
fstab_args=",noauto"
tar xfp "$ROOTFS_TARBALL" -C "$ROOTFS" ./boot/MLO
tar xfp "$ROOTFS_TARBALL" -C "$ROOTFS" ./boot/u-boot.img
touch "$ROOTFS/boot/uEnv.txt"
umount "$ROOTFS/boot"
fi
# In the general case, its enough to just unpack the ROOTFS_TARBALL
# onto the ROOTFS. This will get a system that is ready to boot, save
# for the bootloader which is handled later.
tar xfp "$ROOTFS_TARBALL" --xattrs --xattrs-include='*' -C "$ROOTFS"
# For f2fs the system should not attempt an fsck at boot. This
# filesystem is in theory self healing and does not use the standard
# mechanisms. All other filesystems should use fsck at boot.
fspassno="1"
if [ "$ROOT_FSTYPE" = "f2fs" ]; then
fspassno="0"
fi
# Void images prefer uuids to nodes in /dev since these are not
# dependent on the hardware layout. On a single board computer this
# may not matter much but it makes the cloud images easier to manage.
echo "UUID=$ROOT_UUID / $ROOT_FSTYPE defaults 0 ${fspassno}" >> "${ROOTFS}/etc/fstab"
if [ -n "$BOOT_UUID" ]; then
echo "UUID=$BOOT_UUID /boot $BOOT_FSTYPE defaults${fstab_args} 0 2" >> "${ROOTFS}/etc/fstab"
fi
# This section does final configuration on the images. In the case of
# SBCs this writes the bootloader to the image or sets up other
# required binaries to boot. In the case of images destined for a
# Cloud, this sets up the services that the cloud will expect to be
# running and a suitable bootloader. When adding a new platform,
# please add a comment explaining what the steps you are adding do,
# and where information about your specific platform's boot process
# can be found.
info_msg "Configuring image for platform $PLATFORM"
case "$PLATFORM" in
bananapi*|cubieboard2*|cubietruck*)
@ -227,6 +277,12 @@ ci20*)
dd if="${ROOTFS}/boot/u-boot.img" of="${LOOPDEV}" obs=1K seek=14 >/dev/null 2>&1
;;
GCP*)
# Google Cloud Platform image configuration for Google Cloud
# Engine. The steps below are built in reference to the
# documentation on building custom images available here:
# https://cloud.google.com/compute/docs/images/import-existing-image
# The images produced by this script are ready to upload and boot.
# Setup GRUB
mount_pseudofs
chroot "${ROOTFS}" grub-install "${LOOPDEV}"
@ -258,21 +314,34 @@ GCP*)
rm -f "${ROOTFS}/etc/ssh/*key*"
rm -f "${ROOTFS}/etc/ssh/moduli"
# Force hte hostname since this isn't read from DHCP
# Force the hostname since this isn't read from DHCP
echo void-GCE > "${ROOTFS}/etc/hostname"
;;
esac
# Release all the mounts, deconfigure the loop device, and remove the
# rootfs mountpoint. Since this was just a mountpoint it should be
# empty. If it contains stuff we bail out here since something went
# very wrong.
umount -R "$ROOTFS"
losetup -d "$LOOPDEV"
rmdir "$ROOTFS" || die "$ROOTFS not empty!"
# We've been working with this as root for a while now, so this makes
# sure the permissions are sane.
chmod 644 "$FILENAME"
# The standard images are ready to go, but the cloud images require
# some minimal additional post processing.
case "$PLATFORM" in
GCP*)
# This filename is mandated by the Google Cloud Engine import
# process, the archive name is not.
mv void-GCP*.img disk.raw
info_msg "Compressing disk.raw"
tar Sczf "${FILENAME%.img}.tar.gz" disk.raw
# Since this process just produces something that can be
# uploaded, we remove the original disk image.
rm disk.raw
info_msg "Sucessfully created ${FILENAME%.img}.tar.gz image."
;;