How to use sudo inside a docker container?

Question

Normally, docker containers are run using the user root. I\'d like to use a different user, which is no problem using docker\'s USER directive. But this use

Answer 1

Unlike accepted answer, I use usermod instead.

Assume already logged-in as root in docker, and "fruit" is the new non-root username I want to add, simply run this commands:

apt update && apt install sudo
adduser fruit
usermod -aG sudo fruit

Remember to save image after update. Use docker ps to get current running docker's and , then run docker commit -m "added sudo user" to save docker image.

Then test with:

su fruit
sudo whoami

Or test by direct login(ensure save image first) as that non-root user when launch docker:

docker run -it --user fruit 
sudo whoami

You can use sudo -k to reset password prompt timestamp:

sudo whoami # No password prompt
sudo -k # Invalidates the user's cached credentials
sudo whoami # This will prompt for password