When running in RAM, you can click on the "save" desktop icon and click the "Save Session" button to save the session immediately. Normally, you would be asked at shutdown. The problem with doing an immediate save, is that it can't actually happen immediately, as the permanent storage, /mnt/wkg/.session, (actually, now /mnt/wkg/.session/session1) is mounted as a read-only layer in overlayfs. It cannot be written to. The workaround was to save it to an intermediate folder, /mnt/wkg/.session-tr...
