Other Help Topics :: Safe to remove all /tmp files?
/opt/jre1_5_0 is shown as 2048 bytes because that is the size of the mountpoint. You'll probably see the same size for any mounted uci package. The actual program is much larger. /tmp/jre1_5_0 is, i assume, the mydsl package itself. As long as it's mounted you cannot remove it.
original here.