Debian package commands

# apt-get check # update cache and check for broken packages
$ apt-cache search pattern # search package from text description
$ apt-cache policy package # package priority/dists information
$ apt-cache show -a package # show description of package in all dists
$ apt-cache showsrc package # show description of matching source package
$ apt-cache showpkg package # package information for debugging
# dpkg --audit|-C # search for partially installed packages
$ dpkg {-s|--status} package ... # description of installed package
$ dpkg -l package ... # status of installed package (1 line each)
$ dpkg -L package ... # list filenames installed by the package

Referenced from http://www.debian.org/doc/manuals/reference/ch-package.en.html