I always forget how to upgrade my awful Dir-300 router. Let’s dump the process here:
Download last release. The file name usually matches the pattern openwrt-atheros-combined.squashfs.img
scp openwrt-atheros-combined.squashfs.img into /tmp/
Type sysupgrade /tmp/openwrt-atheros-combined.squashfs.img . You can add the -n flag to get rid of your previous settings.
Tip: If the router run out of space, you can free some RAM by doing:
echo 3 > /proc/sys/vm/drop_caches