But how do you add the key when you never received it? Believe it or not, there is a simple solution for that task.

I’m going to assume you have the PPA added to to your /etc/apt/sources.list file (or added them with the command sudo add-apt-repository ppa:chromium-daily.). After the PPA has been added, the next step before the installation of the software, is to run the command sudo apt-get update. If the key hasn’t been added an error will be displayed indicated the key is missing. When that error pops up, that particular PPA can not be used. The error will look like:

GPG error: http://ppa.launchpad.net lucid Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2524246B1CC723DB

The clue here is the last string of characters, which is the public key. In order to add the key for this particular PPA (or repository), issue the command:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys KEY_ID

Where KEY_ID is the last string of characters in the error (in this case 2524246B1CC723DB).

When the above command is issued, the following output will be displayed:

Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /etc/apt/secring.gpg --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --recv-keys 2524246B1CC723DBgpg: requesting key 1CC723DB from hkp server keyserver.ubuntu.comgpg: key 1CC723DB: public key "Launchpad PPA for Chris Coulson" importedgpg:

Total number processed: 1gpg: imported: 1  (RSA: 1)

The important part of the above output is the final line, indicated that 1 of 1 key was processed. That PPA (or repository) can now be used.

Finding repos and PPA

There are plenty of repositories and PPAs out there. One very good place to start (other than Google) is Launchpad. When you go to launchpad you can search under Registered PPAs, Published sources, Active PPAs, and Published binaries. This site also breaks down PPAs according to release, which includes 6.06 to 11.04. Of course this is a Ubuntu-only site, so those repositories will only work for Ubuntu and distributions based on Ubuntu.

GUI

There is a GUI called gui-apt-key. You can find that in Synaptic (search for “gui-apt-key”,  mark it for installation, and click Apply to install.) This tool basically allows you to take the key ID, enter it in a small text area, and push the Add button in order to add a key to your keyring. If you prefer a GUI tool, it’s a good route to go. Personally, I prefer using the command line, as it is more reliable and more flexible.

Final thoughts

Sometimes those apt errors can be a real pain. But when the error is a missing key, there is always a quick solution for adding that key.

Npackd, which is pronounced unpacked, queries a server on the Internet on startup to retrieve the latest application database. It populates a table with those information that includes the application’s title, description, version and information whether the application is installed on the system, and if it is if it was installed externally or from within Npackd.

The package manager can only manage files that have been installed from the application interface which means that it is not possible to update or uninstall programs that have not been installed using Npackd.

A search form and filter is available on the left. It is for instance possible to only display installed or not installed applications.

A click on the install button at the top installs any selected application on the system. Uninstalls and updates work in a similar fashion.

The application list offers 424 applications at the time of writing, of which some are listed with multiple versions. some of the popular programs include iTunes, utorrent, Winamp, Wireshark, Imgburn, Foxit Reader, Firefox or Dropbox.

All applications are freely available. The installation and uninstallation is completely automated and requires no user interaction.

Programs are listed with status information, installed applications are listed as installed, updates are indicated with the update status and so on.

A link to the homepage of each software is listed in the program database as well. A click on go to package page opens the homepage of the selected application in the default web browser.

It is currently not possible to selected multiple applications for installation. Options to display specific application categories or to create application profiles that can be exported and imported could improve the application further.

That aside, using Npackd is still a lot faster than installing programs manually on the operating system. Interested users can download Npackd from its Google Code project page.

Some of these terms might seem very basic to a few readers and some of them not so basic. It is important, however, that we are all standing on common ground and not having to “google” a term all the time. This article will not be exhaustive, it will cover a few terms. In later “Get to know Linux” articles we will cover more of these terms. Without further adieu, let’s proceed.

~/ or users’ home: This is the directory, created when you either install your operating system or create a new user (with the right arguments), that holds all of your personal data. This directory is created based on what is in the /etc/skel directory. This is the one directory your user has full permissions in. From the command line, the fastest way to get to this directory is to enter the command cd.

Kernel: This is the heart of Linux. In fact some purists will tell you that this IS Linux and everything else is nothing more than various applications built to run on top of Linux. The Linux kernel is a true preemptive multi-tasking kernel, is written in C, and is the single largest “application” on your system. Without the kernel you would not have a Linux operating system. “Back in the day” you would hear Linux users talk about “rolling their own kernel” or “compiling their own kernel”. This referred to building a kernel to meet specific needs. At one time this was almost a necessity for many users. This is not so much the case now as the modern kernel contains just about everything you would need.

Distribution: A distribution of Linux is a bundled variation of Linux. There are a number of major distributions such as: Ubuntu, Fedora, SuSE, Debian. There are also a far greater number of minor distributions: PCLinuxOS,  Linux Mint, Elive, Gentoo, etc. Each distribution has its own selling point. For example: Ubuntu is one of the best known distributions for new users. On the other hand of the spectrum, Gentoo is for highly experienced users. You will often here the term “distro” used in place of “distribution”.

Terminal, Console, or Terminal Emulator: This is where commands are entered. There are really two places this is done: In a terminal window or a Console. Often these terms are exchanged, but there is a difference. A terminal window is generally a small application (like gnome-terminal or xterm) that allows you to enter commands. The console is actually the command line version of the Linux interface. To get to what is typically called “console mode” you would either have to go to a virtual console (using <Ctrl><Alt>F1-0) or log out of X and kill your graphical log in (such as gdm). When your monitor shows nothing but your bash prompt, you are in “console mode”.

X: This term stands for X Window System. In simplest terms, X provides the graphical interface for Linux. Of course it is much more complex than that. The X Windows system alone wouldn’t offer you much functionality as X only provides the framework for the GUI. Running only X would give you a grayish screen, a cursor, and not much more. What you don’t see is that X provides the very foundation that enables your window managers and desktops to do what they do. You will often here the phrase “Log out of X” which, for the purposes of the end user, means log out of your desktop.

Package Manager: One of the key selling points for distributions is which package manager they use. A package manager is the system which applications are automatically installed, removed, and generally managed on a system.Two of the major package management systems for Linux: dpkg and rpm. The dpkg was originally for Debian systems but is now employed by Ubuntu and others as well. RPM was created for the Red Hat Linux distribution but now is used by Fedora, SuSE, and others. Each of these systems have both command line tools (such as apt and apt-get for dpkg, and yum for RPM) and GUI tools (such as gpk-application for RPM and Synaptic for dpkg).

Final thoughts

There you have a few of the terms you should be familiar with when using the Linux operating system. We will continue with more terms at a later date. If you would like to request terms to be defined (or if you would like to request a Linux topic in general), please feel free to contact me.