Environment variables are crucial in Linux operating systems acting as a large repository of information that determines the system and applications behavior as well as the configurations inherent to the operating system. This guide includes all aspects, starting from the definition of temporary variables used only for one command execution to the usage of permanent environment variables in every session. By following this guide, you’ll learn how to have control over your environment, perform system management, and improve security for sensitive data on your Linux system.
1. What are Environment Variables in Linux?
Environment variables are key-value pairs in Linux that applications, processes, and the operating system use to access configuration settings dynamically. These variables simplify system administration by centralizing settings that software and scripts can reference to determine system behavior.
They serve the role of providing processes and applications with defining parameters by which they can regulate their operation. They include but are not limited to, system paths such as PATH, which determines where the system will look for the executable files and configuration parameters for the software in question. Environment variables provide an extensible configuration style, where an application can be constructed to deal with settings and locations and do not contain coded values. It is particularly helpful in the development and multi-user context, where certain variables are set based on the preceding user, application, or runtime characteristics.
Types of Environments in Linux:
There are two types of environments used in linux.
System-wide variables: These apply across all users and processes on the system, making them ideal for settings that need to be universal, such as library paths or application configurations. Stored in global configuration files like.
/etc/environment 
or
/etc/profile.
- User-specific variables: User-specific variables reside in user-level configuration files, such as.
.bashrcor
.bash_profileThe policies are unique to each user and refer to a limited number of freedom rights. It will help each user to set their preferences separately from all general system settings which is important in shared systems as well as in development environments.
Choosing the correct type and storage location for environment variables is essential to maintain security, usability, and system efficiency.
2. Common Commands to Set Environment Variables
Linux has many commands that help to create and set up environment variables. As applied, these commands help make variable-setting dynamic via setting the variables in real-time or for later use in subsequent work sessions in response to other tasks at hand.
Using export
The export command is the primary method for defining environment variables in a Linux shell. When you use export, the variable becomes available to the current session and any child processes. For example:
export VARIABLE_NAME="value"
This command sets VARIABLE_NAME with the specified value, making sure that any processes or scripts launched from the current shell can access it. For example:
export JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"Setting Temporary Variables with env
The env command allows the execution of certain system-assembled equations for just one command without saving, which makes it suitable for tasks that require a temporary variation of the given environment variable. For example:
env VARIABLE_NAME="value" command
After the command executes, the variable is discarded. This approach is helpful for testing or running commands with custom configurations without modifying the environment permanently.
Where to Save Persistent Variables in Linux?
To make a created environment variables exist in the subsequent session, store them in a profile or configuration file. While files such as .bashrc or .bash_profile store the variables of specific users, global variables are stored in the/etc/environment or /etc/profile. The persistent variable is actually more static than the Term; it gives the application and script a place to search for the configuration settings and their value each time it is required.
3. Temporary Environment Variables in Linux
They are known as temporary environment variables and they help the user to make a quick environment alteration for a single session exercise or before running a set of tests. These variables are convenient when testing new configurations with no prior intention to store them as new permanent settings.
Command-line Basics for Temporary Variables
Setting a temporary environment variable is straightforward in Linux. Assign a value to the variable in the command line:
VARIABLE_NAME="temporary_value"
This command creates VARIABLE_NAME with the assigned value for the current session. When you close the terminal, the variable is removed. Temporary variables are particularly useful when experimenting with configuration changes or performing tests without impacting the overall system environment.
Setting Temporary Variables with set and env
Set: The set command lists all active shell and environment variables, making it a useful tool for reviewing your current configuration.
Env: Using env to set temporary variables for specific commands is ideal when running commands that need unique configurations. For example:
env TEMP_VAR="123"
This command assigns TEMP_VAR to 123 for all commands. Both commands allow users to tailor the environment quickly and without permanent changes, ideal for short-term tasks or one-off operations.
4. Setting Persistent Environment Variables
Environment variables are variables or parameters that are used in computing to refer to the environment; it is always present regardless of the shell session, which makes it appropriate for constants like PATH changes or software.
Profile and Shell Configuration Files
Profile and shell configuration files define environment variables that load with each new session:
- User-specific files (~/.bashrc, ~/.bash_profile): Applied only to individual users and allow personal environment customization.
- System-wide files (/etc/environment, /etc/profile): Loaded for all users, setting global values.
Knowing which file to edit allows users and administrators to customize their environment appropriately, making it easier to maintain consistent and efficient configurations.
Setting Variables in .bashrc and .bash_profile
User-specific variables are typically saved in .bashrc or .bash_profile to ensure they load with each new shell session. To add a variable, open .bashrc or .bash_profile with a Text editor:
nano ~/.bashrcAdd the variable:
export VARIABLE_NAME="value"
Run source ~/.bashrc to apply the changes immediately. .bashrc loads with interactive shells, while .bash_profile is loaded only for login shells, offering flexibility based on the session type.
.bashrc is executed for each interactive shell session, while .bash_profile is run only for login shells, providing flexibility based on the session type.
System-wide Variables in /etc/environment and /etc/profile
To set variables for all users, use the system-wide configuration files. Edit /etc/environment or /etc/profile to add global environment variables:
sudo nano /etc/environment
In /etc/environment, add variables without export, like so:
VARIABLE_NAME="value"
Site-wide configuration files mean variables are available to everyone and every session, so such variables are good for settings such as paths, which many users need.
5. Editing Environment Variables
Special environment variables that sometimes require changing settings, directories in PATH, or configuration. In Linux, it is flexible to change variables, whether the changes are meant to be temporary or the changes are more lasting.
Updating Existing Variables:
To change that particular environment variable then reassign the variable to a new value in the shell or a configuration file. For example, if JAVA_HOME is set to an incorrect path, update it with:
export JAVA_HOME="/new/path"
Make the update persistent by editing the .bashrc, .bash_profile, or /etc/environment, then reloading the file using the source.Â
This process keeps configurations accurate, ensuring applications can locate dependencies and run correctly.
Appending Paths to PATH
The system uses the PATH variable to determine the directories where executable files are located. To add a new directory to PATH, use:
export PATH=$PATH:/new/directory
This command keeps the present PATH and then appends the/new/directory to it. To make it persistent, add the line in $HOME/.bashrc or in /etc/environment. Appending paths to PATH is less time-consuming as it provides a command line interface without typing the path of the custom applications and scripts.
6. Advanced Tips and Best Practices
Managing environment variables involves following best practices for security, troubleshooting, and system optimization. Sensitive data, like API keys, should be carefully managed to avoid unauthorized access, and variable issues should be troubleshooted systematically.
Security Tips for Sensitive Data
Environment variables may contain lots of important information, so it is necessary to proceed with caution. Never put your data in a place where everyone can access them easily. For shell configuration files, chown can be used to limit shell access to authorized users alone. In contrast, for the entire system, the use of chmod is recommended in order to ensure that only allowed permissions are granted. In case of storing sensitive values, use secure ones, such as encrypted configuration files or secret management tools. Restriction of raw values and strings increases the levels of protection from both organized hacking and accidental exposure in multi-tenant / live contexts.
Troubleshooting Environment Variable Issues
Some of the common problems with environment variables include incorrect evaluation or missing values in the variables, which may interrupt operations. Echo $VARIABLE_NAME is most commonly used for checking values and paths of files and making sure what you are editing is of the correct shell. Customarily, uses env to display all the currently set environment variables in the current terminal session and also reloads configuration files whenever there is a change with the source. Corrective approaches and methodologies result in steady-state settings and assure the essential use of environment variables in applications and processes.
By mastering environment variables, you gain powerful control over Linux configurations, enabling a secure, dynamic, and optimized environment across sessions. Whether defining paths, customizing user settings, or securing sensitive information, following these practices will help you work efficiently in Linux.
About the writer
Vinayak Baranwal wrote this article. Use the provided link to connect with Vinayak on LinkedIn for more insightful content or collaboration opportunities.
