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install package

apt-get install packagename

search package

apt-cache search packagename or packagedescription

remove package

(with dependencies)

apt-get remove packagename

purge package

(remove without dependencies and delete config files)

apt-get purge packagename

update package-cache

apt-get update

upgrade packages

(without pulling new dependencies)

apt-get upgrade

upgrade the whole distribution

apt-get dist-upgrade