Nerdy Weekly

Thoughts on programming and other stuff that matters



Installing programs in Ubuntu

This article will not only explain how to install stuff, but it will (hopefully) also give readers a better understanding about Linux’s structure for storing and executing programs, ultimately appreciate the usefulness of package managers in general.

Executables

Let’s start with something simple. Fire up your favorite text editor and create a file called itc.sh with the following content:

#!/bin/bash

notify-send "Hello world!"

Let’s say I put it at the desktop. Now open up a terminal, go to the Desktop directory and make our itc file executable. In case you’re new, here are the commands:

cd /home/your_username/Desktop
chmod +x itc.sh

Protip: for the first command you can also type cd ~/Desktop, because ~ is the shorthand for your home directory (/home/username)

With the chmod command, we made it possible to run our little script by typing its full path:

~/Desktop/itc.sh

Another shorthand to make your life easier: . stands for “current directory”, meaning if you are currently in the ~/Desktop directory, you can run the script by simply typing:

./itc.sh

Either way, a notification saying “Hello world!” should pop up. This is a program in its simplest form: an executable file. In this particular example it is a Bash script, but it’s not limited to that. It can be a Python or Ruby script, or a compiled binary file. The file extension isn’t even needed. You can rename it to simply itc and it should run just fine.

In order to run a file, you need to make it executable. This can be done with the chmod command or via the GUIusing Nautilus’s Properties dialog.

Path

So we’ve created a program that shows a useless message, good job! However, every time we call it, we need to specify the whole address to the file: ~/Desktop/itc is probably not a very cool looking command. In order to make it possible to simply run itc, you need to move it to the /usr/bin/ directory. This requires root permission so we’ll need sudo too:

sudo mv ~/Desktop/itc /usr/bin/itc

We can now run our program by simply typing itc. You guessed it: every executable file put in this directory will be available as a command. There are other directories like this too. You can see a whole list of such directories by typing echo $PATH to your terminal.

To make an executable file available as a command, shove it into a directory that’s included in $PATH

Packages

Unfortunately, most programs have a lot of files instead of one, and they are scattered to many different folders. Let’s have a look at the files of wget - the downloader that’s included in every major Linux distribution:

Wget files

It’s not that the developers chose to annoy us by scattering them all over the place. It’s simply complying to Linux structure: executable files go to /usr/bin, man pages (user manuals that show up when you type man wget) go to /usr/share/man, and so on. For more complex programs, the number of files alone is terrifying, which makes installing and remove the program a nightmare.

On another note, almost every Linux program depends on one or many other programs. This is because of the UNIX philosophy that encourages writing each program to do one thing, and do it well. The goal is to make each program easier to implement and maintain as well as to avoid duplicate work. For example, program A may provide a functionality that both programs B and C need. Otherwise, B and C developers both have to write code for one same functionality. In this case, A is called a dependency of B and C. However, this introduces a bunch of problems:

  • We need to install A before installing B
  • We should know not to install A again when we install C
  • We must be careful not to remove A if we are still using B or C
  • What if B and C require different versions of A?
  • I can go on…

This is where packages jump in. A package is basically the whole set of files of a program (or a part of a program). It also stores necessary information such as which file goes to which directory, what are the dependencies of this package, etc. A special program reads the package, installs dependencies and puts files into their appropriate locations. This is called a package manager. Of course besides installing, a package manager also manages updates and removals of programs. Ubuntu is based on Debian, so it inherits Debian’s great package manager called aptitude (or simply apt). Let’s take a look at wget’s dependencies:

Wget files

The package manager maintains a list of available packages and their dependency/dependant relationships. For Ubuntu, the list is updated regularly on Canonical’s official servers. Everytime Ubuntu does the “Check for updates” thing, it is downloading the latest list of packages. And when Ubuntu updates, it is simply pulling newer versions of the installed packages from Canonical’s servers too. These servers are called repositories. All other major Linux distributions do the same thing: letting the package manager and the repositories work on their thing, saving users time to do more interesting stuff.

Here are some basic commands to get you started:

  • sudo apt-get install package-name to install package
  • sudo apt-get remove package-name - it’s obvious isn’t it?
  • sudo apt-get update - update package list. Note that it only updates the list, not the packages
  • sudo apt-get upgrade - upgrade packages to their latest versions

There will be programs that are not available on the official repositories, but are provided as package files (Dropbox for example). Remember that the right package format for Ubuntu is .deb files. Do not open .rpm files since they are for Fedora’s package manager called yum. When you’ve obtained the file, simply open it with Ubuntu Software Center to start installing.

Synaptic, Ubuntu Software Center

Aptitude is only a command-line program, which is not very user-friendly. Synaptic is a GUI program that provides a nice user interface that’s easy to use, while internally it uses apt to do all the actual work.

Wget files

Ubuntu Software Center is more than a GUI wrapper for apt. It is something similar to Apple’s appstore with all those program ratings and promotions. It’s nice for beginners but the fact that it hides the details like dependency list makes it undesirable for intermediate users. If you are comfortable with Synaptic, I strongly recommend using it as your main way to install/uninstall stuff. But ultimately, using the command-line apt always is the fastest way.


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