Master Linux Environment Variables: Quick Configurations & Loading Order

Linux environment variable configuration

When installing software manually, you often need to set environment variables; the following lists several ways to do so.

System: Ubuntu 14.0

Username: uusama

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

Linux reading environment variables

Methods to read environment variables: export – shows all currently defined environment variables. echo $PATH – prints the value of the PATH variable.

Running these commands yields:

uusama@ubuntu:~export
declare -x HOME="/home/uusama"
declare -x LANG="en_US.UTF-8"
declare -x LANGUAGE="en_US:"
declare -x LESSCLOSE="/usr/bin/lesspipe %s %s"
declare -x LESSOPEN="| /usr/bin/lesspipe %s"
declare -x LOGNAME="uusama"
declare -x MAIL="/var/mail/uusama"
declare -x PATH="/home/uusama/bin:/home/uusama/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
declare -x SSH_TTY="/dev/pts/0"
declare -x TERM="xterm"
declare -x USER="uusama"

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 defines the search path for executable commands, separated by colons ( :). When defining it with export, quotes are optional.

Linux environment variable configuration method 1: export PATH

Use the export command to modify PATH directly, e.g., to add MySQL:

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

Notes:

Effective time: immediate

Effective duration: only the current terminal session

Scope: current user only

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

Linux environment variable configuration method 2: vim ~/.bashrc

Edit the user’s ~/.bashrc file:

vim ~/.bashrc

# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Notes:

Effective time: when a new terminal is opened or after running source ~/.bashrc Effective duration: permanent

Scope: current user only

If another startup file later overwrites PATH, this change may not take effect.

Linux environment variable configuration method 3: vim ~/.bash_profile

Similar to ~/.bashrc, add the new path at the end of ~/.bash_profile (or ~/.profile on some systems):

vim ~/.bash_profile

# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Notes:

Effective time: when a new terminal is opened or after running source ~/.bash_profile Effective duration: permanent

Scope: current user only

If ~/.bash_profile does not exist, edit ~/.profile or create a new file.

Linux environment variable configuration method 4: vim /etc/bashrc

This system‑wide method requires root or write permission:

# make the file writable if needed
chmod -v u+w /etc/bashrc

vim /etc/bashrc

# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Notes:

Effective time: after opening a new terminal or running source /etc/bashrc Effective duration: permanent

Scope: all users

Linux environment variable configuration method 5: vim /etc/profile

Another system‑wide file, edited similarly:

# make the file writable if needed
chmod -v u+w /etc/profile

vim /etc/profile

# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Notes:

Effective time: after opening a new terminal or running source /etc/profile Effective duration: permanent

Scope: all users

Linux environment variable configuration method 6: vim /etc/environment

System environment file, also requires root:

# make the file writable if needed
chmod -v u+w /etc/environment

vim /etc/environment

# add at the end
export PATH=$PATH:/home/uusama/mysql/bin

Notes:

Effective time: after opening a new terminal or running source /etc/environment Effective duration: permanent

Scope: all users

Linux environment variable loading principle analysis

Environment variables are defined either by the user or system‑wide files.

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

System‑level files: /etc/bashrc, /etc/profile (or /etc/bash_profile), /etc/environment When a user logs in, the shell reads ~/.bash_profile (or ~/.profile); if absent, it reads ~/.bash_login, then proceeds to ~/.bashrc.

Testing Linux environment variable loading order

To test the load order, add a variable UU_ORDER at the top of each file, appending the file name to its value:

/etc/environment

/etc/profile

/etc/profile.d/test.sh

/etc/bashrc (or /etc/bash.bashrc)

~/.bash_profile (or ~/.profile)

~/.bashrc export UU_ORDER="$UU_ORDER:/etc/environment" After saving, open a new terminal and run echo $UU_ORDER:

uusama@ubuntu:~$ echo $UU_ORDER
/etc/environment:/etc/profile:/etc/bashrc:/etc/profile.d/test.sh:~/.profile:~/.bashrc

The observed loading sequence is:

/etc/environment

/etc/profile

/etc/bash.bashrc

/etc/profile.d/test.sh

~/.profile

~/.bashrc

Linux environment variable file loading details

Overall order: system environment → user custom environment.

/etc/environment -> /etc/profile -> ~/.profile

/etc/profile

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

# /etc/profile: system-wide .profile file for the Bourne shell (sh)
if [ "$PS1" ]; then
  if [ "$BASH" ] && [ "$BASH" != "/bin/sh" ]; then
    # The file bash.bashrc already sets the default PS1.
    if [ -f /etc/bash.bashrc ]; then
      . /etc/bash.bashrc
    fi
  else
    if [ "`id -u`" -eq 0 ]; then
      PS1='# '
    else
      PS1=' '
    fi
  fi
fi

if [ -d /etc/profile.d ]; then
  for i in /etc/profile.d/*.sh; do
    if [ -r i ]; then
      . i
    fi
  done
  unset i
fi

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

# if running bash
if [ -n "${BASH_VERSION}" ]; then
  # include .bashrc if it exists
  if [ -f "HOME/.bashrc" ]; then
    . "HOME/.bashrc"
  fi
fi

# set PATH so it includes user's private bin directories
PATH="HOME/bin:HOME/.local/bin:PATH"

~/.profile

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

Some small tips

You can create a custom environment file (e.g., uusama.profile) with a series of export statements and source it from ~/.profile to have those variables available on every login.

Aliases can also be defined, such as alias rm="rm -i", and added to ~/.profile for convenient use.