Where are Environment Variables stored in Ubuntu

The environment variables can be stored in various configuration files depending upon the program that you are referring to as well the scope - system-wide or user-specific.

System-Wide Environment Variables:

You can find the system-wide environment variables under /etc/environment file.

# cat /etc/environment

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:
     /usr/games:/usr/local/games:/snap/bin"

User-Specific Environment Variables:

Based on what shell you use, you can find them under the ~/.bashrc or ~/.zshrc files under the home directory.

Example:

cat ~/.bashrc

# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
[ -z "$PS1" ] && return

# don't put duplicate lines in the history. See bash(1) for more options
# ... or force ignoredups and ignorespace
HISTCONTROL=ignoredups:ignorespace

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

Know the Temporary Environment variables:

If you are looking for the temporary environment variables set for the current session then you can make use of the printenv command.

Example:

# printenv

HOSTNAME=b9fc21f2fc40
HOME=/root
TERM=xterm
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/home/user/bin
DEV_SERVER_URL=https://192.167.8.2:8000
PWD=/