init

#!/bin/sh

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/opt/local/bin:/opt/local/sbin

FUSE_OPT="-o default_permissions -o allow_other -o use_ino -o nonempty -o suid"
UNION_OPT="-o cow"

SSD_DEVICE="/dev/nvme0n1p1"
SSD_PATH="/ssd"
UNIONFS="/usr/bin/unionfs-fuse"

ulimit -n 16384

# mount ssd
mount -n -t ext4 -o defaults ${SSD_DEVICE} ${SSD_PATH}

unionmount()
{
  DEST=$1
  MASTER="${SSD_PATH}/master/${DEST}"
  OVERLAY="${SSD_PATH}/overlay/${DEST}"
  UNION="${SSD_PATH}/union/${DEST}"

  mount -n --bind "/${DEST}" "/${MASTER}"
  
  ${UNIONFS} ${FUSE_OPT} ${UNION_OPT} "/${OVERLAY}=RW:/${MASTER}=RO" "/${UNION}"
  mount -n --bind "/${UNION}" "/${DEST}"
}

unionmount_ro()
{
  DEST=$1

  unionmount "${DEST}"
  mount -o remount,ro "/${DEST}"
}

# unionmount etc
unionmount home
unionmount opt
unionmount var

exec /lib/systemd/systemd "$@"