Implement workaround for low-mem models.

The installer makes a backup (in memory) of itself to /bootfs, but after
restore to the new FAT32 partition doesn't remove that memory copy.
The 256MB model is so memory constrained that it fails, likely due to
an OOM problem. For those models (only), remove the RAM copy and when
the new boot partition gets mounted (to /rootfs/boot), make a
'mount --bind' to /bootfs, so for all intend and purposes the rest
should still work the same.

Signed-off-by: Diederik de Haas <[email protected]>

scripts/etc/init.d/rcS

@@ -1119,6 +1119,25 @@ sync
 umount /boot || fail
 log_msg_end "OK"
 
+model_memory=$(busybox free -m | grep "^Mem:" | awk '{print $2}')
+low_mem_model=""
+if [ "$model_memory" -le "260" ] ; then
+    low_mem_model="true"
+else
+    low_mem_model="false"
+fi
+log_msg "Model memory in MB: '$model_memory' is a low mem model: '$low_mem_model'"
+
+if [ "$low_mem_model" = "true" ] ; then
+    log_msg_start "Removing backup copy in /bootfs... "
+    rm -r -- /bootfs/*
+    log_msg_end "OK"
+else
+    log_msg "Keeping backup copy in /bootfs"
+fi
+
+print_mem_info
+
 # only do modprobe if the module is NOT built into the kernel
 if [ "$(grep -c $rootfstype /lib/modules/"$(uname -r)"/modules.builtin)" -eq 0 ]; then
     log_msg_start "Loading $rootfstype module... "
@@ -1137,6 +1156,12 @@ mkdir /rootfs/boot || fail
 mount $bootpartition /rootfs/boot || fail
 log_msg_end "OK"
 
+if [ "$low_mem_model" = "true" ] ; then
+    log_msg_start "Bind mount /rootfs/boot to /bootfs... "
+    mount --bind /rootfs/boot /bootfs
+    log_msg_end "OK"
+fi
+
 print_mem_info
 
 log_msg "Starting install process..."
@@ -1694,6 +1719,11 @@ chmod 0640 /rootfs/var/log/raspbian-ua-netinst.log
 
 log_msg_start "Unmounting filesystems... "
 
+if [ "$low_mem_model" = "true" ] ; then
+    log_msg_inline "removing bind mount to /bootfs... "
+    umount /bootfs
+fi
+
 umount /rootfs/boot
 umount /rootfs
 log_msg_end "OK"