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 user should be able to use sudo inside the container. This command is missing.

Here's a simple Dockerfile for this purpose:

FROM ubuntu:12.04

RUN useradd docker && echo "docker:docker" | chpasswd
RUN mkdir -p /home/docker && chown -R docker:docker /home/docker

USER docker
CMD /bin/bash

Running this container, I get logged in with user 'docker'. When I try to use sudo, the command isn't found. So I tried to install the sudo package inside my Dockerfile using

RUN apt-get install sudo

This results in Unable to locate package sudo

Barbicel

Just give sudo group to user. askubuntu.com/questions/7477/… – Dissociable

Answer 1

Just got it. As regan pointed out, I had to add the user to the sudoers group. But the main reason was I'd forgotten to update the repositories cache, so apt-get couldn't find the sudo package. It's working now. Here's the completed code:

FROM ubuntu:12.04

RUN apt-get update && \
      apt-get -y install sudo

RUN useradd -m docker && echo "docker:docker" | chpasswd && adduser docker sudo

USER docker
CMD /bin/bash

Barbicel

doesn't work in centos. the adduser command spits out the usage help for useradd – Lightweight

For CentOS, you could add a user and group, then create a shard file under /etc/sudoers.d/ and set the permissions to 440 on that file. Then the user would have sudo access under CentOS, 6 and up. 5 you'll have to add the #includedir /etc/sudoers.d directive in /etc/sudoers – Milks

Doesn't work for me. I have those errors: E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied) E: Unable to lock directory /var/lib/apt/lists/ – Cheke

This doesnt seem to be working for Ubuntu 18.04 docker image – Applesauce

My user is called bot. Is the right adaptation of your commands: ` RUN useradd -m bot RUN echo "bot:bot" | chpasswd RUN && adduser docker sudo` maybe explaining echo "docker:docker" | chpasswd && adduser docker sudo would have helped. – Cayes

Does not work. sudo: a terminal is required to read the password – Antinode

adduser creates a new user. To add the docker user to the sudo group, use usermod -a -G sudo docker. – Reprise

add what user to sudoers ? what user runs the docker "RUN" commands? – Hardiman

Answer 2

When neither sudo nor apt-get is available in the container, you can also jump into running container as root user using command:

docker exec -u root -t -i container_id /bin/bash

Whoopee

This is a much better solution to what the OP probably wants to achieve, even though the accepted answer gives the requested solution. At the very least, it's the answer I was looking for! – Hardback

This is the best answer, instead of doing it the hard way with the dockerfile. – Manville

+1 I had an issue in changing permission inside docker.. Came to know that only root user can perform this action and this is the only way to accomplish it. In this way, no sudo is required for me! – Algeciras

Somebody give this man a medal – Luke

In case you can not use /bin/bash then use /bin/sh instead. 'docker exec -u root -t -i container_id /bin/sh' – Zampino

this looks nice but when I get into my container nothing seems to have ebeen installed? docker pull brandojazz/iit-term-synthesis:test then docker run -u root -ti brandojazz/iit-term-synthesis:test_arm bash. Why? #73736008 – Cayes

This didn't work for me. This did: docker exec -u 0 -it container_id bash – Colostrum

Best answer for sure! – Ionogen

Answer 3

The other answers didn't work for me. I kept searching and found a blog post that covered how a team was running non-root inside of a docker container.

Here's the TL;DR version:

RUN apt-get update \
 && apt-get install -y sudo

RUN adduser --disabled-password --gecos '' docker
RUN adduser docker sudo
RUN echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers

USER docker

# this is where I was running into problems with the other approaches
RUN sudo apt-get update 

I was using FROM node:9.3 for this, but I suspect that other similar container bases would work as well.

Citarella

I am using ubuntu:bionic-20180724.1. I used this approach but, after the above, it does not allow me to install another package. I appended one line to the above Dockerfile in order to install a package with: RUN apt-get install -y tree. However, it gave me this error message: Step xxxx/xxxx : RUN apt-get install -y tree ---> Running in j5e6gsvwfafa Reading package lists... E: Could not open lock file /var/lib/apt/lists/lock - open (13: Permission denied) E: Unable to lock directory /var/lib/apt/lists/ – Integral

@WR I think you need to change that line to read RUN sudo apt-get install -y tree. After setting the USER to something other than root, you'll need to use sudo for any commands that require root privileges. – Citarella

Answer 4

For anyone who has this issue with an already running container, and they don't necessarily want to rebuild, the following command connects to a running container with root privileges:

docker exec -ti -u root container_name bash

You can also connect using its ID, rather than its name, by finding it with:

docker ps -l

To save your changes so that they are still there when you next launch the container (or docker-compose cluster) - note that these changes would not be repeated if you rebuild from scratch:

docker commit container_id image_name

To roll back to a previous image version (warning: this deletes history rather than appends to the end, so to keep a reference to the current image, tag it first using the optional step):

docker history image_name
docker tag latest_image_id my_descriptive_tag_name  # optional
docker tag desired_history_image_id image_name

To start a container that isn't running and connect as root:

docker run -ti -u root --entrypoint=/bin/bash image_id_or_name -s

To copy from a running container:

docker cp <containerId>:/file/path/within/container /host/path/target

To export a copy of the image:

docker save container | gzip > /dir/file.tar.gz

Which you can restore to another Docker install using:

gzcat /dir/file.tar.gz | docker load

It is much quicker but takes more space to not compress, using:

docker save container | dir/file.tar

And:

cat dir/file.tar | docker load

Hyperborean

Using docker exec and docker commit to create a new image is not an especially maintainable path; if you need to recreate the image for any reason (say there's a security issue in the original base image) these manual steps won't be tracked anywhere. – Mcnulty

Are you saying it would be better to put the commands in the Dockerfile or entrypoint and rebuild? I might be misunderstanding your point, I do start with 'For anyone who has this issue with an already running container, and they don't necessarily want to rebuild', and I specifically warn the moment we can't backtrack. I have added your warning 'these changes would not be repeated if you rebuild from scratch'. Is there anything else you would add? – Hyperborean

Answer 5

if you want to connect to container and install something
using apt-get
first as above answer from our brother "Tomáš Záluský"

docker exec -u root -t -i container_id /bin/bash

then try to

RUN apt-get update or apt-get 'anything you want'

it worked with me hope it's useful for all

Awaken

Answer 6

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 <CONTAINER ID> and <IMAGE>, then run docker commit -m "added sudo user" <CONTAINER ID> <IMAGE> 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 <IMAGE>
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

Cleavable

Answer 7

If SUDO or apt-get is not accessible inside the Container, You can use, below option in running container.

docker exec -u root -it f83b5c5bf413 ash

"f83b5c5bf413" is my container ID & here is working example from my terminal:

Restorative

Answer 8

Here's how I setup a non-root user with the base image of ubuntu:18.04:

RUN \
    groupadd -g 999 foo && useradd -u 999 -g foo -G sudo -m -s /bin/bash foo && \
    sed -i /etc/sudoers -re 's/^%sudo.*/%sudo ALL=(ALL:ALL) NOPASSWD: ALL/g' && \
    sed -i /etc/sudoers -re 's/^root.*/root ALL=(ALL:ALL) NOPASSWD: ALL/g' && \
    sed -i /etc/sudoers -re 's/^#includedir.*/## **Removed the include directive** ##"/g' && \
    echo "foo ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers && \
    echo "Customized the sudoers file for passwordless access to the foo user!" && \
    echo "foo user:";  su - foo -c id

What happens with the above code:

• The user and group foo is created.
• The user foo is added to the both the foo and sudo group.
• The uid and gid is set to the value of 999.
• The home directory is set to /home/foo.
• The shell is set to /bin/bash.
• The sed command does inline updates to the /etc/sudoers file to allow foo and root users passwordless access to the sudo group.
• The sed command disables the #includedir directive that would allow any files in subdirectories to override these inline updates.

Ecclesiastical

Answer 9

The main idea is that you need to create user that is a root user according to the container.

Main commands:

RUN echo "bot:bot" | chpasswd
RUN adduser bot sudo

the first sends the literal string bot:bot to chpasswd which creates the user bot with the password bot, chpasswd does:

The chpasswd command reads a list of user name and password pairs from standard input and uses this information to update a group of existing users. Each line is of the format:

user_name:password

By default the supplied password must be in clear-text, and is encrypted by chpasswd. Also the password age will be updated, if present.

The second command I assume adds the user bot as sudo.

Full docker container to play with:

FROM continuumio/miniconda3
# FROM --platform=linux/amd64 continuumio/miniconda3

MAINTAINER Brando Miranda "[email protected]"

RUN apt-get update \
  && apt-get install -y --no-install-recommends \
    ssh \
    git \
    m4 \
    libgmp-dev \
    opam \
    wget \
    ca-certificates \
    rsync \
    strace \
    gcc \
    rlwrap \
    sudo

# https://github.com/giampaolo/psutil/pull/2103

RUN useradd -m bot
# format for chpasswd user_name:password
RUN echo "bot:bot" | chpasswd
RUN adduser bot sudo

WORKDIR /home/bot
USER bot
#CMD /bin/bash

Cayes

i get the follwoing error when running the dockerfile : /bin/sh: useradd: not found . No idea why – Theocentric

Answer 10

This may not work for all images, but some images contain a root user already, such as in the jupyterhub/singleuser image. With that image it's simply:

USER root
RUN sudo apt-get update

Lipography

for the image "fabric8/java-centos-openjdk8-jdk" just adding USER root before the RUN command solved my problem, didn't even need to add the sudo – Ima

Answer 11

If you have a container running as root that runs a script (which you can't change) that needs access to the sudo command, you can simply create a new sudo script in your $PATH that calls the passed command.

e.g. In your Dockerfile:

RUN if type sudo 2>/dev/null; then \ 
     echo "The sudo command already exists... Skipping."; \
    else \
     echo -e "#!/bin/sh\n\${@}" > /usr/sbin/sudo; \
     chmod +x /usr/sbin/sudo; \
    fi

Tyche

Depending on the docker images you are using (in my case Ubuntu:18.04), you might need to remove the -e from the echo. Otherwise it will be present in the file itself, rendering it infunctional. – Thadthaddaus

Neat idea, but this will not work if the original command is using sudo options, such as sudo -E ls. It will try to execute -E ls. – Franci

Answer 12

An example Dockerfile for Centos7. In this example we add prod_user with privilege of sudo.

FROM centos:7

RUN yum -y update && yum clean all

RUN yum -y install openssh-server  python3 sudo

RUN adduser -m prod_user && \
    echo "MyPass*49?" | passwd prod_user --stdin && \
    usermod -aG wheel prod_user && \
    mkdir /home/prod_user/.ssh && \
    chown prod_user:prod_user -R  /home/prod_user/ && \
    chmod 700 /home/prod_user/.ssh

RUN echo "prod_user ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers && \
    echo "%wheel ALL=(ALL) ALL" >> /etc/sudoers

RUN echo "PasswordAuthentication yes" >> /etc/ssh/sshd_config

RUN systemctl enable sshd.service

VOLUME [ "/sys/fs/cgroup" ]

ENTRYPOINT ["/usr/sbin/init"]

Cleareyed

Answer 13

There is no answer on how to do this on CentOS. On Centos, you can add following to Dockerfile

RUN echo "user ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/user && \
    chmod 0440 /etc/sudoers.d/user

Buckra

But this command still failed: bash Step 6/8 : RUN echo "user ALL=(root) NOPASSWD:ALL" > /etc/sudoers.d/user && chmod 0440 /etc/sudoers.d/user ---> Running in daea0aae031c /bin/sh: 1: cannot create /etc/sudoers.d/user: Permission denied – Rottweiler

This essentially makes your "non-root" user equivalent to root, so long as an attacker knows to preface their commands with sudo. It's very marginally better than running as root, but not something I'd generally recommend in a Docker setup. – Mcnulty

Answer 14

I'm using an Ubuntu image, while using the docker desktop had faced this issue.

The following resolved the issue:

1. apt-get update
2. apt-get install sudo

Fives