When opkg tries to install a package but fails (this can occur if, for example, your router runs out of space during installation, which can happen because opkg only naively checks space requirements), it doesn't clean up after itself.
This script looks up all files that would have been installed by a specific package, and if they exist, it deletes them.
Based on this gist.
wget https://github.com/codebling/openwrt-utils/raw/master/opkg-cleanup.sh
sh opkg-cleanup.sh to view usage
sh opkg-cleanup.sh <packages>
where is a list of (space-separated) packages (which were partially installed) to clean up.