When one runs sudo, he actually starts a new environment as the root user, so any environment variables in current shell environment will not be transferred to the new root user environment.

To transfer current environment variables to the new environment, one can run the following command:

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curVar="variable in current environment"
sudo -E echo $curVar
# output: "variable in current environment"

Here the option -E lets the sudo to preserve user’s environment, so the variable curVar is visible in sudo.

However, the environment variable PATH is special, itself will still be visible in the new environment, but will not affect where sudo to find its command, even with the -E option, because when sudo is called, it finds a variable ‘secure_path’ in the file ‘/etc/sudoers’ (for Ubuntu) and use that value as the ‘PATH’ variable. The ‘secure_path’ normally looks like this:

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secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

One can use sudo visudo to edit this file to add additional directories for sudo to use.

An alternative solution is below:

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# assume there is a executable '/opt/bin/hello' 
PATH=/opt/bin:$PATH
sudo -E echo $PATH # you can see the PATH contains /opt/bin
sudo -E hello # but this fails
# a workout is
sudo env "PATH=$PATH" hello

The above command lets sudo calls env, and env creates a new environment by setting ‘PATH=$PATH’. In the env set environment, it runs the executable ‘hello’. The trick here is that ‘hello’ is run in env’s environment, not sudo’s environment.

Happy programming 😄

References

1. A stackexchange post on this issue: https://unix.stackexchange.com/questions/442747/why-do-the-following-ways-to-preserve-environment-variables-for-sudo-not-work

2. Another post: https://superuser.com/questions/709515/command-not-found-when-using-sudo

Last modified on 2021-06-09