Passing Environment Variables to Sudo Command

Suppose you have a bash script that sets an environment variable, and then invokes something with sudo:

#!/bin/bash
export MY_VAR=test
sudo /do/something

You will quickly notice that the environment variable you set using export is not available to the /do/something command when it is invoked by sudo.

When you run sudo, you are actually starting a new environment as the root user (or whatever user you have instructed sudo to run as), so any environment variables that exist in your current shell will not be passed to the sudo command. There are two ways to get around this.

Tell sudo to preserve environment

The sudo command has a handy argument -E or --preserve-env which will pass all your environment variables into the sudo environment.

Passing only select environment variables to sudo

A better approach is to just pass the environment variables you want to preserve, instead of passing everything. There are two ways to accomplish this, first you can supply a list of environment variable names to the --preserve-env argument. For example:

sudo --preserve-env=HOME /usr/bin/env

Finally you can also set environment variables directly in the sudo command, like this:

sudo ZEBRA=true /usr/bin/env

Passing multiple environment variables to sudo

If you don't want to pass all environment variables to sudo, but do want to pass more than one, you can simply comma separate them, for example:

sudo --preserve-env=HOME,PATH /usr/bin/env

The above passes both the HOME and the PATH environment variables to sudo.

Testing if an environment variable is passed to sudo

Sometimes you need to test that an environment variable was really passed though sudo. A great way to test this is with the /usr/bin/env command. This command will simply echo's all the environment variables available to the process. For example if I ran the following command on my mac running as user pete:

sudo --preserve-env=HOME /usr/bin/env

The above command outputs something like the following:

HOME=/Users/pete
USER=root
SUDO_COMMAND=/usr/bin/env
SUDO_USER=pete
...

We can see in the output above that the --preserve-env=HOME argument in sudo did indeed pass the HOME=/Users/pete environment variable, even though USER=root. This trick works great on both linux and macs.