Apt / apt-get

Find out from which deb package a file is

# dpkg -S p11tool
gnutls-bin: /usr/bin/p11tool
gnutls-bin: /usr/share/man/man1/p11tool.1.gz

Add gpg key from url

apt-key adv --fetch-keys <url>

Show info about the package

apt show <package-name>

List available updates

apt list --upgradable

Do everything

apt update && apt dist-upgrade -y && apt autoremove -y && apt autoclean -y && lsof | grep lib | grep DEL && init 6

List the package versions available from all your sources

apt-cache madison <package name>

Search package from local cache

apt-cache search <package name>