The problem description
I have a Docker image, which is being executed with volume mounting options a large number of times. It is built in a way so that the default user does not have root permissions. However I need to make sure that when I mount the volume it is being mounted as root and not as the current working user because of security concerns. (The current working non-root user must not be allowed to delete any files inside the mounted volume.)
Example
From the host machine:
docker run -it -v /path/to/mount:/container/mounting/path image-name
Inside the container current-user#docker-container:
All of the files inside /container/mounting/path must have owner permissions root root and not current-user current-user.
Related
I am trying to run the NVIDIA PyTorch container nvcr.io/nvidia/pytorch:22.01-py3 on a Linux system, and I need to mount a directory of the host system (that I have R/W access to) in the container. I know that I need to use bind mounts, and here's what I'm trying:
I'm in a directory /home/<user>/test, which has the directory dir-to-mount. (The <user> account is mine).
docker run -it -v $(pwd)/dir-to-mount:/workspace/target nvcr.io/nvidia/pytorch:22.01-py3
Here's the error output:
docker: Error response from daemon: error while creating mount source path '/home/<user>/test/dir-to-mount': mkdir /home/<user>/test: permission denied.
ERRO[0000] error waiting for container: context canceled
As far as I know, docker will only need to create the directory to be mounted if it doesn't exist already. Docker docs:
The file or directory does not need to exist on the Docker host already. It is created on demand if it does not yet exist.
I suspected that maybe the docker process does not have access; I tried chmod 777 with dir-to-mount as well as with test, but that made no difference.
So what's going wrong?
[Edit 1]
I am able to mount my user's entire home directory with the same command, but cannot mount other directories inside the home directory.
[Edit 2]
Here are the permissions:
home directory: drwx------
test: drwxrwxrwx
dir-to-mount: drwxrwxrwx
Run the command with sudo as:
sudo docker run -it -v $(pwd)/dir-to-mount:/workspace/target nvcr.io/nvidia/pytorch:22.01-py3
It appears that I can mount my home directory as a home directory (inside of /home/<username>), and this just works.
docker run -it -v $HOME:$HOME nvcr.io/nvidia/pytorch:22.01-py3
I don't know why the /home/<username> path is special, I've tried looking through the docs but I could not find anything relevant.
I want to know how I can add the local users of my server to a docker container. I don't need to import their files, I just need a username/password/privileges with new home directory in the docker container for every user in my system. For example, suppose my docker container contains the following users:
Host System:
admin: who has root access and rw access to all
bob: a regular non-sudo user
joe: another regular non-sudo user
Then the Docker Container must have users:
admin: who has root access and rw access to all
bob: a regular non-sudo user
joe: another regular non-sudo user
The Docker container and the system are both running linux, though the system is red hat and the container is ubuntu.
EDIT: I don't want to mount /etc/ files if possible, as this can create a two way security vulnerability as pointed out by #caveman
You would have to mount all relevant linux files using -v like /etc/passwd, /etc/shadow, /ect/group, and /etc/sudoers. Though I can't recommend this due to the security risks, if anyone gets root access in the container they can add users on the host or change passwords since he mount works both ways.
The list of files is not exhaustive, for example, you have to also make sure the shell exacutables exist within the container. When testing this I had to make a symbolic link from /usr/bin/zsh to /bin/bash for example since my user has the zsh shell configured which was not present in the docker image.
If you want to use these users to interact with mounted files, you also have to make sure that user namespace remapping is disabled, or specify that you want to use the same user namespace as the host with the --userns=host flag. Again, not recommended since it is a security feature, so use with care.
Note: Once you have done all this you can use su - {username} to switch to all your existing users. The -u options doesn't work since docker checks the /etc/passwd file before mounting and will give an error.
We have a docker container running in Linux VMs. This container is writing the logs inside a directory in the container.
Container log directory - /opt/log/
This directory in volume mounted to host machine so that all the log files will also be available in host.
Host directory - /var/log/
Here we see container is creating the log files with 600 (-rw-------+) permission. There is no group read permission assigned to these files.
Same permissions are reflecting in host directory also. We need to add group read permission (640) (-rw-r-----+) automatically for all the files getting created in this directory so that other logging agents can read these files.
I have tried setting ACL also for adding this permission on host but these permissions are not getting set for the files inside this directory.
setfacl -Rdm g::r-- /var/log/
Is there a way we can add group read permission automatically for all the files getting created in this host directory?
From the following article,
https://dille.name/blog/2018/07/16/handling-file-permissions-when-writing-to-volumes-from-docker-containers/
There is a parameter to set the user id and the group id for example,
docker run -it --rm --volume $(pwd):/source --workdir /source --user $(id -u):$(id -g) ubuntu
To set the permissions of the user, when starting the container.
I am extending a docker image of a program from here and I want to change some configs and create my own docker image. I have written a Dockerfile as follows and replaced the server.xml file in this image:
FROM exoplatform/exo-community
COPY server.xml /opt/exo/conf
RUN chmod 777 /opt/exo/conf/server.xml
When I created the docker image and run an instance from the image, the running program of the container cannot access the file server.xml because its owner is the root user and I see the permission denied error. I tried to change the ownership in the Dockerfile by chmod command but I see the Operation not permitted error. The user of the running container is not the root user and it cannot access the server.xml file that is owned by the root user. How can I resolve this issue?
If this is actually just a config file, I wouldn't build a custom image around it. Instead, use the docker run -v option to inject it at runtime
docker run \
-v $PWD/server.xml:/opt/exo/conf/server.xml \
... \
exoplatform/exo-community
(You might still hit the same permission issues.)
In your Dockerfile approach, the base image runs as an alternate USER but a COPY instruction by default makes files owned by root. As of relatively recent Docker (18.03; if you're using Docker 1.13 on CentOS/RHEL 7 this won't work) you should be able to
COPY --chown=exo server.xml /opt/exo/conf
Or if that won't work, you can explicitly switch to the root user and back
COPY server.xml /opt/exo/conf
USER root
RUN chown exo /opt/exo/conf/server.xml
USER exo
i'm running a docker container inside my server .
in my server (host) i ve this folder : /opt/myapp/myFolder
where myFolder has 755 permissions and myuser:mygroup ownership
I'm using docker-compose to run my container , thus i'm mounting that same volume
mycontainer:
...
volumes:
- /opt/myapp/myFolder:/opt/myapp/myFolder
...
The probleme that , inside my container , my directory "myFolder" still having the same host permissions (755) but not the same ownership
and the ownership looks like this 65534:65534
this results on permission denied in some other treatment inside this folder.
normally inside the container "myFolder" still keeping the same host ownership .
Note : tthe user myuser and the group mygroup do exist inside the container.
Suggestions ?
Docker doesn't create users and groups to match the mounted folder's ownership.
You can add the user inside your container to the folder's group, using the group id (GID).
Check out "Docker and file system permissions" article.