tweaks to see if i can get overlayfs working happy with systemd.

see https://projects.archlinux.org/archiso.git/commit/?id=a637bdb8574168ab4cddef13d5de7f458650bda5, changes to archiso/initcpio/hooks/archiso

extra/pre-build.d/etc/mkinitcpio.d/linux.preset

@@ -1,15 +0,0 @@
-# mkinitcpio preset file for the 'linux' package
-
-ALL_config="/etc/mkinitcpio.conf"
-ALL_kver="/boot/vmlinuz-linux"
-
-#PRESETS=('default' 'fallback')
-PRESETS=('default')
-
-#default_config="/etc/mkinitcpio.conf"
-default_image="/boot/initramfs-linux.img"
-#default_options=""
-
-#fallback_config="/etc/mkinitcpio.conf"
-#fallback_image="/boot/initramfs-linux-fallback.img"
-#fallback_options="-S autodetect"

extra/pre-build.d/usr/lib/initcpio/hooks/archiso-custom

@@ -11,13 +11,19 @@ _mnt_fs() {
     ro_dev=$(losetup --find --show --read-only "${img}")
     echo ${ro_dev} >> /run/archiso/used_block_devices
     ro_dev_size=$(blockdev --getsz ${ro_dev})
+    if [[ "${cowfile_size}" == "100" ]]; then
+        rw_dev_size=${ro_dev_size}
+    else
+        # size calculation done in this way to avoid integer overflow when ro_dev_size is > 10.2G
+        rw_dev_size=$((ro_dev_size/100*cowfile_size))
+    fi
 
     if [[ "${cow_persistent}" == "P" ]]; then
         if [[ -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow" ]]; then
             msg ":: Found '/run/archiso/cowspace/${cow_directory}/${img_name}.cow', using as persistent."
         else
             msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as persistent."
-            truncate -s "${cowfile_size}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
+            dd of="/run/archiso/cowspace/${cow_directory}/${img_name}.cow" count=0 seek=${rw_dev_size} &> /dev/null
         fi
     else
         if [[ -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow" ]]; then
@@ -25,13 +31,13 @@ _mnt_fs() {
             rm -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
         fi
         msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as non-persistent."
-        truncate -s "${cowfile_size}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
+        dd of="/run/archiso/cowspace/${cow_directory}/${img_name}.cow" count=0 seek=${rw_dev_size} &> /dev/null
     fi
 
     rw_dev=$(losetup --find --show "/run/archiso/cowspace/${cow_directory}/${img_name}.cow")
     echo ${rw_dev} >> /run/archiso/used_block_devices
 
-    dmsetup create ${dm_snap_name} --table "0 ${ro_dev_size} snapshot ${ro_dev} ${rw_dev} ${cow_persistent} 8"
+    echo "0 ${ro_dev_size} snapshot ${ro_dev} ${rw_dev} ${cow_persistent} 8" | dmsetup create ${dm_snap_name}
 
     _mnt_dev "/dev/mapper/${dm_snap_name}" "${newroot}${mnt}" "-w"
     echo $(readlink -f /dev/mapper/${dm_snap_name}) >> /run/archiso/used_block_devices
@@ -102,7 +108,9 @@ run_hook() {
     [[ -z "${dm_snap_prefix}" ]] && dm_snap_prefix="arch"
     [[ -z "${archisodevice}" ]] && archisodevice="/dev/disk/by-label/${archisolabel}"
     if [[ -z "${cowfile_size}" ]]; then
-        cowfile_size="256M"
+        cowfile_size="100"
+    else
+        cowfile_size=${cowfile_size/%}
     fi
 
     if [[ -n "${cow_label}" ]]; then
@@ -168,7 +176,7 @@ archiso_mount_handler() {
 
     _mnt_sfs "/run/archiso/bootmnt/${archisobasedir}/${arch}/airootfs.sfs" "/run/archiso/sfs/airootfs"
    # _mnt_fs "/run/archiso/sfs/airootfs/airootfs.img" "${newroot}" "/"
-    mount --bind "/run/archiso/sfs/airootfs" "/new_root"
+    mount --bind "run/archiso/sfs/airootfs" "/new_root"
 
     if [[ "${copytoram}" == "y" ]]; then
         umount /run/archiso/bootmnt