https://askubuntu.com/questions/17823/how-to-list-all-installed-packages

apt list --installed

dpkg --get-selections | grep <bla>
dpkg --get-selections | grep -v deinstall >list.txt

dpkg --get-selections > list.txt

# clear: to deinstall any packages not in list given to following --set-selections.
dpkg --clear-selections
sudo dpkg --set-selections < list.txt

https://askubuntu.com/questions/160897/how-do-i-search-for-available-packages-from-the-command-line

apt-cache search <keyword>

apt-cache depends <package_name>
apt-cache rdepends <package_name>

• https://superuser.com/questions/82923/how-to-list-files-of-a-debian-package-without-install
• https://askubuntu.com/questions/160897/how-do-i-search-for-available-packages-from-the-command-line
• https://askubuntu.com/questions/32507/how-do-i-get-a-list-of-installed-files-from-a-package

sudo apt-get install apt-file
sudo apt-file update

apt-file list <package_name>
# apt-file list pigpiod

apt-cache search <keyword>
# apt-cache search rabbitmq

dpkg -L <package_name>   # -L == --listfiles
# dpkg -L librabbitmq-dev

see https://www.cyberciti.biz/faq/equivalent-of-rpm-qf-command/

dpkg -S <file>

apt-get --reinstall install <package>