use overlayfs for guests

etc/fstab

+# /etc/fstab: static file system information.
+#
+# Use 'blkid' to print the universally unique identifier for a
+# device; this may be used with UUID= as a more robust way to name devices
+# that works even if disks are added and removed. See fstab(5).
+#
+# <file system> <mount point>   <type>  <options>       <dump>  <pass>
+# / was on /dev/md0 during installation
+UUID=89d0aa85-a88c-4f47-8846-5dcb4557aad9 /               ext4    errors=remount-ro 0       1
+# swap was on /dev/sda2 during installation
+UUID=dbca6dca-2246-48c1-a5f5-61116391ef8e none            swap    sw,pri=1              0       0
+# swap was on /dev/sdb2 during installation
+UUID=1b43d051-9a20-493b-82ea-bfc693403b79 none            swap    sw,pri=1              0       0
+
+# readonly gasttemplate. because we need 777 rights on this files for the guests 
+/home/gasttemplate.img /home/gasttemplate ext4 ro 0 0
+# gastaccount overlayfs. see https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt
+overlay /home/gast1 overlay lowerdir=/home/gasttemplate,upperdir=/home/gast1.writable,workdir=/home/gast1.workdir 0 0
+overlay /home/gast2 overlay lowerdir=/home/gasttemplate,upperdir=/home/gast2.writable,workdir=/home/gast2.workdir 0 0
+
+
+/dev/sr0        /media/cdrom0   udf,iso9660 user,noauto     0       0
+/dev/sdc1       /media/usb0     auto    rw,user,noauto  0       0
+/dev/sdc2       /media/usb1     auto    rw,user,noauto  0       0

root/gast1-session.sh

 #!/bin/bash
-rm -rf /home/gast1
-cp -a /home/gasttemplate /home/gast1
-chown -R gast1: /home/gast1
+# old style template copy
+#rm -rf /home/gast1
+#cp -a /home/gasttemplate /home/gast1
+#chown -R gast1: /home/gast1
+
+# clean guest overlayfs
+# unmount and mount, because random shit can happen
+umount /home/gast1
+rm -r /home/gast1.writable/* /home/gast1.writable/.[!.]* /home/gast1.writable/..?* || true
+mount /home/gast1
+chown gast1: /home/gast1/.PlayOnLinux/wineprefix/battlenet

root/gast2-session.sh

 #!/bin/bash
-rm -rf /home/gast2
-cp -a /home/gasttemplate /home/gast2
-chown -R gast2: /home/gast2
+# old style template copy
+#rm -rf /home/gast1
+#cp -a /home/gasttemplate /home/gast1
+#chown -R gast1: /home/gast1
+
+# clean guest overlayfs
+# unmount and mount, because random shit can happen
+umount /home/gast2
+rm -r /home/gast2.writable/* /home/gast2.writable/.[!.]* /home/gast2.writable/..?* || true
+mount /home/gast2
+chown gast2: /home/gast2/.PlayOnLinux/wineprefix/battlenet