Apt-get/dpkg

Command Summary

• apt-get - install and remove stuff

  apt-get install package 

  install package

  apt-get install package=version 

  install specified version of package

  apt-get update  

  update sources

  apt-get upgrade 

  upgrade all upgradeable packages

  apt-get dist-upgrade 

  upgrade all upgradeable packages, including installing new packages where dependencies have changed

  apt-get remove package 

  remove package

• apt-cache - find information on packages

  apt-cache search regexp 

  search packages names and descriptions for regexp

  apt-cache show package 

  show package info

  apt-cache policy package 

  show installed and available versions of package

• apt-file - look for files contained within packages

  apt-file update 

  update file contents lists

  apt-file search string 

  search package contents for file name/path containing string

  apt-file list package 

  list files in package

• dpkg - information on installed packages

  dpkg -s package 

  show status of package

  dpkg -L package 

  list files in package

  dpkg --get-selections 

  list all installed packages

• wajig - wrapper for apt-get, dpkg, dpkg-deb, apt-cache, and other tools

  wajig hold package 

  stop package being upgraded as part of normal upgrade or dist-upgrade

  wajig unhold package 

  revert held status of package

Solving public key errors

Errors like:

W: GPG error: http://packages.freecontrib.org edgy-plf Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F120156012B83718
W: You may want to run apt-get update to correct these problems

can be fixed by finding out the location for the relevant sites public key, and installing the key using:

wget http://packages.freecontrib.org/ubuntu/plf/12B83718.gpg -O- | sudo apt-key add -