Master Linux Environment Variables: 6 Proven Configuration Methods

Linux Environment Variable Configuration

When installing software on Linux, you often need to add its binaries to the environment so the system can locate them. The examples below assume Ubuntu 14.0, user uusama, and a MySQL binary directory /home/uusama/mysql/bin.

System: Ubuntu 14.0

Username: uusama

MySQL path to add: /home/uusama/mysql/bin

Reading Environment Variables

export

– displays all currently defined environment variables. echo $PATH – prints the value of the PATH variable.

uusama@ubuntu:~$ export
declare -x HOME="/home/uusama"
declare -x LANG="en_US.UTF-8"
... (other variables) ...
declare -x PATH="/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

uusama@ubuntu:~$ echo $PATH
/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

The PATH variable lists directories separated by colons; export can be used with or without double quotes.

Method 1: export PATH

Directly modify PATH with the export command.

export PATH=/home/uusama/mysql/bin:$PATH
# or put the new directory first
export PATH=$PATH:/home/uusama/mysql/bin

Effective immediately.

Only affects the current terminal session.

Applies to the current user.

Remember to include the original $PATH to avoid overwriting existing entries.

Method 2: Edit ~/.bashrc

Append an export line to the user’s ~/.bashrc file.

vim ~/.bashrc
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective when a new terminal is opened or after running source ~/.bashrc.

Permanent for the user.

May be overridden by later configuration files.

Method 3: Edit ~/.bash_profile

Similar to ~/.bashrc, but used by login shells.

vim ~/.bash_profile
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective when a new login shell starts or after source ~/.bash_profile.

Permanent for the user.

If ~/.bash_profile does not exist, edit ~/.profile instead.

Method 4: Edit /etc/bashrc

System‑wide configuration; requires root privileges.

# make the file writable
chmod -v u+w /etc/bashrc
vim /etc/bashrc
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective for new terminals or after source /etc/bashrc.

Permanent.

Applies to all users.

Method 5: Edit /etc/profile

Another system‑wide file, similar to /etc/bashrc.

# make the file writable
chmod -v u+w /etc/profile
vim /etc/profile
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective for new terminals or after source /etc/profile.

Permanent.

Applies to all users.

Method 6: Edit /etc/environment

System environment file; also requires root.

# make the file writable
chmod -v u+w /etc/environment
vim /etc/environment
# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Effective for new terminals or after source /etc/environment.

Permanent.

Applies to all users.

Linux Environment Variable Loading Principle

Environment variables can be defined at the user level or system level. The system reads files in a specific order, so later definitions can overwrite earlier ones.

User‑level files: ~/.bashrc, ~/.profile (or ~/.bash_profile).

System‑level files: /etc/bashrc, /etc/profile (or /etc/bash_profile), /etc/environment.

During a login, the shell first reads ~/.bash_profile (or ~/.profile), then ~/.bashrc. System files are processed before user files.

Testing the Loading Order

Insert the same line into each file to trace the order:

export UU_ORDER="$UU_ORDER:/path/to/file"

After opening a new shell, run echo $UU_ORDER to see the concatenated list.

$UU_ORDER:/etc/environment:/etc/profile:/etc/bash.bashrc:/etc/profile.d/test.sh:~/.profile:~/.bashrc

/etc/environment

/etc/profile

/etc/bash.bashrc

/etc/profile.d/test.sh

~/.profile

~/.bashrc

File Loading Details

/etc/profile

loads /etc/bash.bashrc and then executes any .sh scripts in /etc/profile.d/:

# /etc/profile snippet
if [ -f /etc/bash.bashrc ]; then
  . /etc/bash.bashrc
fi
if [ -d /etc/profile.d ]; then
  for i in /etc/profile.d/*.sh; do
    [ -r "$i" ] && . "$i"
  done
fi

The user’s ~/.profile includes ~/.bashrc if it exists:

# ~/.profile snippet
if [ -n "$BASH_VERSION" ]; then
  if [ -f "$HOME/.bashrc" ]; then
    . "$HOME/.bashrc"
  fi
fi

~/.profile

is read once at login, while ~/.bashrc is read for each interactive shell.

Additional Tips

Create a custom file (e.g., uusama.profile) with your own variables and source it from ~/.profile for project‑specific settings.

Define command aliases in ~/.profile, such as alias rm="rm -i", to make commands safer.