Installing software in Linux, the "hard" way

Sun, 15 Sep 2024 13:34:18 -0300

Introduction

Picture this: you’re setting up the packages and tools to develop your brand new application. Everything is going smooth, until you found out that one of the softwares you need is only avaliable as package of executable binaries, without any installers and nowhere to be found in your package managers. Seems like quite the overhead, right?

Well, not to worry! Because today we’re out to get our hands dirty and learn how to install ANY PACKAGE in a Linux system ‒ and you might just learn a few new tricks about Linux along the way.

I. Housing the package

The first step to solve our problem is to define where the package will be stored in our system. In practice, you may use any directory you’d like, but to keep things organized, let’s use the /opt directory.

The /opt directory is reserved for installing software and packages that are not part of the system’s core components, i.e, not necessary for your system to function properly.

When installing your package, you should create a new directory (preferably with the package name, like /opt/<package_name>) to avoid mixing up files of different packages.

You may have noticed that inside your package, there’s a /bin directory that contains some executable files. At this point, we can run these files, but we’ll have to specify the full path of the file every time.

II. Make your package avaliable with `$PATH`

To avoid having to pass the full path of the executables each time we run the software, we’ll make use of the $PATH environmental variable to specify the path of our installation.

The $PATH variable is a special shell variable that defines a list of directories where executable files are located. Each directory is delimited by a colon (:)

You may specify new directories in $PATH by exporting the variable with the new value (export PATH=/new/dir/path:$PATH).

Now, there are two ways of adding a executable to $PATH:

Adding a Symlink to the executables

Symlinks are (roughly) files that “point” to other file paths or directories. This allows us to access files accross the file system (and even other file systems), without specifying the full path.

You can create new symlinks using the command ln -s TARGET LINK_NAME, where:

TARGET is the path of the file which the symlink will point to
LINK_NAME is the path where the symlink will be created

To make it avaliable in $PATH, we may create a symlink inside a directory that is already in $PATH. In this case, let’s use the /usr/local/bin directory to store our symlink.

To create our symlink, simply run the following comman:

# Replace the placeholders with the proper names of your directories/files
ln -s /opt/<package_name>/bin/<filename> /usr/local/bin/<filename>

Once created, the executable will be avaliable in your shell. Try it out by typing the name of the symlink in your terminal.

Trade-offs of using symlinks

This approach is pretty straightforward and easy to setup. We don’t need to edit the value of $PATH, thus avoiding possible configuration errors. Also, by placing the symlink inside /usr/local/bin, we make it avaliable for all users of the system.

Unfortunately, there are also drawbacks. If you need to add multiple executables, you’ll need do create one symlink per executable. You may create a symlink to the /bin directory of the package, but you’ll still need to specify the name of the executable.

Links in Linux
Links are a powerful tool in Linux, allowing you to create shortcuts between files and directories, organizing your files easily, and much more. I recommend reading this RedHat post about linking in Linux.

Adding the package directory to `$PATH`

If you want a more robust solution, you may effectivelly edit the $PATH variable to include your package directory. For that, we’ll need to create a configuration file to export our updated $PATH.

The /etc/ directory contains configuration files of system applications, e.g. service management, network, SSH, and many more. Be careful when making changes to files here.

Similar to /opt, Linux also has a directory for storing system-wide configuration files: the /etc directory. Actually, there’s the /etc/opt directory, which is intended to store configuration files for applications installed in /opt.

To create the configuration file, head to /etc/opt and create a new file, named as <package_name>rc. Inside it, paste the following code and replace the placeholders with the correspondent paths:

# Replace "PACKAGE_HOME" with the name of your package
export PACKAGE_HOME=/opt/<package_dir>
export PATH=$PACKAGE_HOME/bin:$PATH

To load the settings into your shell session, run source /etc/opt/<config_file> and check your $PATH variable with echo $PATH. If the directory of your package is there, your configuration file is working.

Now, you might have noticed that the configurations aren’t loaded automatically when you open a new terminal. To address this, simply add this configuration to one of the following files:

# This loads "PACKAGE" into $PATH
[ -f /etc/opt/<config_file> ] && source /etc/opt/<config_file>

For only one user, append the load configuration at the end of ~/.bashrc
For all users, create a shell script (with the .sh suffix) in /etc/profile.d/ with the load configuration

Trade-offs of using `$PATH`

One advantage of this approach is that every executable inside the /bin directory will be avaliable in your shell. Also, you may choose to make it avaliable for only one user or for all users, by simply placing the load configuration in a different file.

However, tweaking with the $PATH variable may break your shell configuration if you’re not careful enough. The same goes for editing files inside /etc/profile.d; it’s best to create a new file rather than edit an existing one.

If you’re installing an application with a graphical interface (not CLI-based), you’ll likely want to add it to your desktop menu for easier access. In this case, we’ll need to take an extra step.

The entries in your desktop menu are located in the /usr/share/applications directory. Each application has a .desktop entry file, containing settings for how it is displayed in the menu.

To add a desktop entry file for your application:

Create a new .desktop entry file with the name of your application

Open the file and add the following configuration, replacing the placeholders with the correct settings:

[Desktop Entry]
Version=1.0
Type=Application
Name=<APP_NAME>
Icon=/opt/<PACKAGE_NAME>/<ICON_FILE>
Exec="/opt/<PACKAGE_NAME>/<EXEC_FILE>" %f
Comment=<APP_DESCRIPTION>
Categories=<KEYWORD1;KEYWORD2;>

Save the file and run sudo update-desktop-database

Now, the application is avaliable in your app menu, without the need to start it through the terminal.

Summary

Install your package in the /opt directory
Use symlinks or edit your $PATH variable to include the package executables for an user or all the system
If the package is not CLI-based, add a .desktop entry file at /usr/share/applications to add the package to your desktop menu

Conclusion

Although application support for Linux platforms is pretty decent today, you’ll eventually come across a situation like the one we’ve discussed here. Also, you can automate this process by creating shell scripts to setup the files for you.

Well, that’s it. Until next time! 👋

Sysadmin on Douglas Domingos :: CompSci@UFCG

Installing software in Linux, the "hard" way

Introduction

I. Housing the package

II. Make your package avaliable with `$PATH`

Adding a Symlink to the executables

Trade-offs of using symlinks

Adding the package directory to `$PATH`

Trade-offs of using `$PATH`

III. Updating the desktop menu (BONUS)

Summary

Conclusion

Sysadmin on Douglas Domingos :: CompSci@UFCG

Installing software in Linux, the "hard" way

Introduction

I. Housing the package

II. Make your package avaliable with $PATH

Adding a Symlink to the executables

Trade-offs of using symlinks

Adding the package directory to $PATH

Trade-offs of using $PATH

III. Updating the desktop menu (BONUS)

Summary

Conclusion

II. Make your package avaliable with `$PATH`

Adding the package directory to `$PATH`

Trade-offs of using `$PATH`