liveusb: overlayfs doesn't support sparse files, use tmpfs directly

This comes with some overhead, at least at the beginning, because all
private images are copied there at system startup (instead of first
use). This uses about 450MB of RAM.
Still better than non-sparse private.img (2GB...).

live/livesys

@@ -104,16 +104,38 @@ if ! strstr "`cat /proc/cmdline`" nopersistenthome && [ -n "$homedev" ] ; then
 else
   mkdir -p /home/qubes
   mount -t tmpfs none /home/qubes
+  chown root:qubes /home/qubes
+  chmod 2775 /home/qubes
 fi
 
-mkdir -p /home/qubes/qubes
-mkdir -p /home/qubes/workdir
-ln -nsf /var/lib/qubes-base/vm-templates /home/qubes/qubes/vm-templates
-mount -t overlay overlay \
-          -o lowerdir=/var/lib/qubes-base \
-          -o upperdir=/home/qubes/qubes \
-          -o workdir=/home/qubes/workdir \
-          /var/lib/qubes
+# overlay fs doesn't handle sparse files:
+#   fs/overlayfs/copy_up.c:94     /* FIXME: copy up sparse files efficiently */
+# So for now it is useless here. But some day...
+# 
+#mkdir -p /home/qubes/qubes
+#mkdir -p /home/qubes/workdir
+#ln -nsf /var/lib/qubes-base/vm-templates /home/qubes/qubes/vm-templates
+#mount -t overlay overlay \
+#          -o lowerdir=/var/lib/qubes-base \
+#          -o upperdir=/home/qubes/qubes \
+#          -o workdir=/home/qubes/workdir \
+#          /var/lib/qubes
+
+ln -nsf /var/lib/qubes-base/vm-templates /home/qubes/vm-templates
+ln -nsf /var/lib/qubes-base/vm-kernels /home/qubes/vm-kernels
+for dir in /var/lib/qubes-base/*; do
+    dir=`basename $dir`
+    case $dir in
+        vm-templates) ;;
+        vm-kernels) ;;
+        *)
+            if [ ! -e /home/qubes/$dir ]; then
+                cp -a /var/lib/qubes-base/$dir /home/qubes/
+            fi
+            ;;
+    esac
+done
+mount --bind /home/qubes /var/lib/qubes
 
 /usr/bin/qvm-prefs --offline-mode -s sys-net pcidevs '[]'
 for dev in $(/sbin/lspci -mm -n | sed -ne 's/^\([0-9][0-9]:[0-9][0-9].[0-9]\) "02.*/\1/p'); do