How to pass environment variables to a Docker container?
It is always a good practice to separate the app from its configuration. It is not a good idea to have a database login credential defined as variables in the code of the application. This is why we use environment variables. But this means we need a way to pass the value somehow to the application running in the Docker container.
There are two main ways to inject environment variables into Docker containers.
Using the command line argument -env
or -e
When you launch docker using the docker run
command, you can pass the
environment variables as a key-value pair using the -env
(or -e
) option.
docker run --name ubuntu -env VARIABLE='value' -d ubuntu
If you have a variable already exported like this:
export VARIABLE='value'
You can pass the variable into the docker like this:
docker run --name ubuntu -env VARIABLE -d ubuntu
Using the .env
file
Passing the variable using the command option argument is easy for a small
number of variables. If you need to pass many variables at the same time, it is
always better to use .env
file.
The .env
file (also called envfile) is a simple text file in which the
variables are defined as key-value pairs.
You can append variables to envfile using the following syntax:
echo VARIABLE1='value1' > envfile.txt
echo VARIABLE2='value2' >> envfile.txt
echo VARIABLE3='value3' >> envfile.txt
Please, notice the >>
operator when appending to an existing file. Using the
>
operator would overwrite the content.
-
Copy SSH key to clipboard
An SSH key is usually stored in the form of a file. To copy an SSH key to your clipboard, you can use one of the following options: Option 1 - Copy from terminal The first option is to print the ke...
Questions -
How do I disable ipv6 on Ubuntu 20.04
To disable IPv6 on your Ubuntu 20.04 system, open the /etc/sysctl.conf file in your favorite text editor and put the following lines at the end of the file: net.ipv6.conf.all.disableipv6 = 1 net.ip...
Questions -
Error Permission denied (publickey) when I try to ssh
This error appears when trying to SSH into a server. The publickey in the brackets after the error message is misleading. One reason might be wrong configuration in sshd_config file and the second ...
Questions -
Nginx on Ubuntu
Here is how to install Nginx on Ubuntu 20.04 in under two minutes: Step 1 - Update the package list on your system The first step is to update the package list on your system before proceeding to a...
Guides
We are hiring.
Software is our way of making the world a tiny bit better. We build tools for the makers of tomorrow.
Help us in making the internet more reliable.

Help us with developer education and get paid.
