Docker daemon permissions to access NFS share

I also tried to modify the « /etc/docker/daemon.json » instead of the one in my previous post, but it still throws an error « unable to configure the Docker daemon with file /etc/docker/daemon.json: the following directives are specified both as a flag and in the configuration file: data-root (from flag: /MyNFS/MountPoint/docker, from file: /MyNFS/MountPoint/docker) »

So I am not sure what should be my next steps.

@wuruwhi welcome to the forums! Glad to have you here and hopefully we can work through the NFS issue with Docker. Let me take a look at the information in the posts you have made and I will get back to you with my thoughts if that sounds good and some troubleshooting steps 👍 

Ok, so a few thoughts here.

Docker needs full control of the data-root directory. So it might need to perform operations that are conflicting with your NFS permissions or the user-level permissions.

Make sure root_squash is not enabled for your NFS export. If it is, change it to no_root_squash temporarily to test if this resolves the issue:

/MyNFS/MountPoint 192.168.x.x(rw,sync,no_root_squash), then restart the NFS server after making your changes. Is this running on a Linux server? If so, you can do something like sudo exportfs -ra
after making your changes.

On the NFS server, make sure your directory /MyNFS/MountPoint/docker is owned by uid=1234 and

gid=1234.
Run the following commands on the NFS server:

sudo chown -R 1234:1234 /MyNFS/MountPoint/docker
sudo chmod -R 775 /MyNFS/MountPoint/docker

Also, make sure your share is mounted with the right options for Docker. Edit your /etc/fstab or mount command to use the following:

nfs defaults,rw,sync 0 0

Make sure your Docker daemon runs with the same user uid=1234. You can do this by modifying your docker.service file to include the directive:

[Service]
user=1234

The last error that you posted there looks like there is conflicting docker configurations. You will want to use either systemd configuration file or the daemon.json file but not both. If you are using systemd configuration, make sure no data-root directive is in your daemon.json file. If you are using the daemon.json file, remove the --data-root flag from your systemd service file if that makes sense.

Once you have made your changes, try to restart the docker service:

sudo systemctl daemon-reload
sudo systemctl restart docker

Also, just a simpler approach to think about. When i am using external storage like NFS, or any other, you don't have to change all your docker storage to use the external storage, but simply bind mount your containers that you want to have stored on your external storage bind mounted to that specific directory. This will simplify your challenges with trying to change the entire Docker data root to be your NFS share. 

So, for example:

version: "3.8"

services:
  app:
    image: nginx:latest
    container_name: container-I-want-on-nfs-storage
    ports:
      - "8080:80"
    volumes:
      - /mnt/nfs_share:/usr/share/nginx/html:rw
    restart: always

The bind mount will make sure the data for your container is stored on NFS while the data-root for docker itself remains the default. This way you can protect your data that you want for those specific containers and not change Docker's data root.