make-rootfs

#!/bin/sh
#
# mkrootfs -- Create an EVE rootfs
#
# Input is a tarball containing the rootfs partition.
# Output is a raw partition on stdout
#
# The following env variables change the behaviour of this script
#     DEBUG - makes this script verbose

set -e
[ -n "$DEBUG" ] && set -x

IMGFILE=/rootfs.img
[ -f "$IMGFILE" ] || EXPORT_CMD="cat $IMGFILE"

# we want everything except the final result to stderr
( exec 1>&2;

  mkdir -p /tmp/rootfs
  cd /tmp/rootfs

  [ -t 0 ] || bsdtar xzf -

  # This _filesystem_ UUID will be later reused as the _partition_
  # UUID when creating the final image. This will allow us to have
  # a static grub configuration.
  ROOTFS_UUID=$(cat /proc/sys/kernel/random/uuid)

  # In what can only be described as a horrible thing, create grub.cfg
  # here. The only place we have to unpack the cmdline given by the
  # yml image is here.
  #
  CMDLINE="$(cat boot/cmdline)"

  sed -i'' -e "/set *linuxkit_cmdline=/s#=.*\$#=$CMDLINE#" EFI/BOOT/grub.cfg

  ROOTFS_BLOCKSZ=4096
  ROOTFS_PART_HEADROOM_BLOCKS=16000
  
  ROOTFS_FILE_SIZE_KB=$(du -sk . | awk '{print $1}')
  ROOTFS_PART_BLOCKS=$(( $ROOTFS_FILE_SIZE_KB / 4 + $ROOTFS_PART_HEADROOM_BLOCKS ))
  ROOTFS_PART_SIZE=$(( $ROOTFS_PART_BLOCKS * $ROOTFS_BLOCKSZ ))
  ROOTFS_PART_SIZE_KB=$(( ( ($ROOTFS_PART_SIZE + 1024) / 1024 * 1024) / 1024 ))
  ROOTFS_PART_SECTORS=$(( $ROOTFS_PART_SIZE_KB * 2 ))

  mksquashfs /tmp/rootfs/ $IMGFILE -noappend
)

$EXPORT_CMD