http://wiki.openwrt.org/doc/howto/generic.sysupgrade says I need to have "as much free RAM as the image is in size plus an some additional MiB of free memory".
Now I am a bit uncler about this, free gives me this:
Mem: 13388 12636 752 0 1292
Swap: 0 0 0
Total: 13388 12636 752
Which is obviously not enough.
However, df gives this:
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 2304 2304 0 100% /rom
tmpfs 6696 60 6636 1% /tmp
tmpfs 512 0 512 0% /dev
/dev/mtdblock3 576 288 288 50% /overlay
mini_fo:/overlay 2304 2304 0 100% /
It says I have 6MB free in tmpfs. Now my image is roughly 3MB in size. Could I make tmpfs smaller and free the three MB that I do not need to store the firmware image? Wiki is a bit unclear about this:-/.
I tried upgrading, but it always failed (the router rebooted itself unupgraded) - I am not sure whether this was the cause.