Installing packages on external storage device on OpenWRT

I've just put a flash memory stick into the OpenWRT device (Asus WL-500g Deluxe) to be able to run bigger application on it. So I formatted to ext3 and mounted. But for some reason however the opkg (the package manager) has been instructed to use this new destination

toma@OpenWrt:~# cat /etc/opkg.conf
src/gz snapshots http://downloads.openwrt.org/kamikaze/8.09.1/brcm-2.4/packages
dest root /
dest ram /tmp
dest opt /opt
lists_dir ext /var/opkg-lists
option overlay_root /jffs

This way:

opkg -d opt install tcpdump

Then I got this nasty message which refers to the root fs instead of the external storage however the -d used to put the package there:

# opkg -d opt install tcpdump
Installing tcpdump (3.9.8-1.1) to opt...
Collected errors:
 * Only have 352 available blocks on filesystem /opt/, pkg tcpdump needs 652

To resolve the issue, I cheated:

option overlay_root /opt

to the /etc/opkg.conf mentioned above already.

Everything went fine with:

# opkg -d opt install tcpdump
Installing tcpdump (3.9.8-1.1) to opt...
Downloading http://downloads.openwrt.org/kamikaze/8.09.1/brcm-2.4/packages/tcpdump_3.9.8-1.1_mipsel.ipk
Connecting to downloads.openwrt.org (78.24.191.177:80)
tcpdump_3.9.8-1.1_mi 100% |**************************************************************************************************************************************************************|   251k 00:00:00 ETA
Configuring tcpdump

Just a foot note, this is pretty handy tool anyway...