dpkg-unhold marks package(s) to be held.
it achieves this by running `dpkg --set-selections' and piping in the package name(s) followed by `install'.
NOTE: this program does not install, remove, purge any package. it ONLY sets the status of the package. any actual removal or purging is done the next time dselect, apt-get, aptitude, etc are run.
The name is little bit of a misnomer in that it marks the package for installation. this effectively "unholds" the package if it is held, but will cause dselect/apt/etc to install it if it wasn't already installed.