http://www.tecmint.com/useful-basic-commands-of-apt-get-and-apt-cache-for-package-management/
https://help.ubuntu.com/community/SwitchingToUbuntu/FromLinux/RedHatEnterpriseLinuxAndFedora

https://help.ubuntu.com/community/AptGet/Howto
https://help.ubuntu.com/community/Repositories/CommandLine

updating/upgrading stuff:
https://linuxize.com/post/how-to-upgrade-to-ubuntu-18-04-bionic-beaver/
    apt-get update
    apt-get upgrade
    apt-get dist-upgrade

    sudo apt-get install update-manager-core
    /etc/update-manager/release-upgrades
        Prompt=normal
    do-release-upgrade
        lsb_release -a
        hostnamectl
        cat /etc/os-release

removing/purging:

apt-get remove
apt-get purge (or remove --purge)

To get rid of stale packages: (/var/cache/apt/archives)

apt-get autoremove (dependencies only which aren't required anymore)
apt-get autoclean (Remove only obsolete packages from the local cache directory)
apt-get clean


Listing files of package:
http://askubuntu.com/questions/32507/how-do-i-get-a-list-of-installed-files-from-a-package
http://superuser.com/questions/82923/how-to-list-files-of-a-debian-package-without-install

dpkg -listfiles <package-name>
dpkg -L <package-name>


List all the installed packages:

https://help.ubuntu.com/community/ReinstallingSamePackages
http://askubuntu.com/questions/17823/how-to-list-all-installed-packages

dpkg --get-selections | grep -v deinstall


gettins sources of package:

apt-get -q source $package


kernels purging:

http://askubuntu.com/questions/2793/how-do-i-remove-or-hide-old-kernel-versions-to-clean-up-the-boot-menu-or-free-sp

uname -r
dpkg --list | grep linux-image
dpkg --list | grep linux-headers
sudo apt-get purge linux-image-x.x.x.x-generic
sudo update-grub2



info, dependencies

apt-cache showpkg
apt-cache depends
apt-cache rdepends

cache stats:

apt-cache stats