Docker Community Forums

Share and learn in the Docker community.

Cannot share a folder with docker container


(Jw123) #1

I am running an interactive python docker container on Ubuntu 14.04 using docker 17.03.1. I want to share files between local host and container so that files I create in the container are visible in the local directory and vice-versa. However when I run the following command and access jupyter notebook, I see an empty working directory in the container with no files. I also don’t see any files created in the container in the local directory.

docker run -e USER=$USER -e USERID=$UID -v /home/watts/python:/home/watts/python -w=/home/watts/python -p 8888:8888 --rm -it watts/python jupyter notebook --no-browser --notebook-dir=/home/watts/python --allow-root

Can someone please tell me what I am doing wrong?

(Sam) #2

should work… can you show us a directory listing?

i do this with my containers … I dont use -e

(Jw123) #3

Please see attached for a directory listing. I get the same result without the -e option.
The /home/watts/python directory on the host machine contains some jupyter notebooks. I want to create new ones as well as run existing ones from the interactive docker container directly to/from the host directory.

(Sam) #4

ok. the folder owner is user watts

when u are logged on with -it, you are running as root I think… whoami will tell you

I don’t know what you mean ‘run’…

(Jw123) #5

I logged into the docker container. The ‘whoami’ command returns ‘docker’. I have tried executing a slightly different command using --user docker as shown below. But I am getting an error.

Please forgive me for using ‘run’. I just meant to be able to execute cells of an jupyter notebook using docker. I can do that once files in the host directory are visible in the docker machine.

watts@Maximus:~/python$ docker run --user docker -v /home/watts/python:/home/watts/python -w=/home/watts/python -p 8888:8888 --rm -it watts/python jupyter notebook --no-browser --ip="*" --NotebookApp.token=’’ --notebook-dir=$PWD --allow-root
docker: Error response from daemon: linux spec user: unable to find user docker: no matching entries in passwd file.
ERRO[0000] error getting events from daemon: context canceled

(Sam) #6

yeh, I don’t know what --user means…

anyhow… still don’t quite understand…

start a container, interactive with volume mapping
docker run -it -v … image_name and parms to image entrypoint command
then at the commandline present by the running container

cd some folder
python some_script_name and parms


(David Maze) #7

The process launched in the Docker container runs as some user ID, by default 0 or whatever was declared as USER in the Dockerfile used to build the image.

The numeric user ID is the only important thing. The container has its own /etc/passwd file, which maps between user names and passwords, and it doesn’t have to agree with the host’s copy of the file. This leads to things like needing to make your shared Web content directory readable by the cups or mysql user, because that happens to have the same numeric user ID as www-data in your container.

The interaction with -v is again tricky, and varies by operating system and installation mechanism. When I last seriously dealt with this a year or two ago, on native Linux numeric user IDs would get passed straight through without trouble (if a host directory was mode 0770 owned by uid 99, then uid 99 in the container had full access), but on Docker Toolbox on a Mac only uid 0 and the uid matching the host system user could access anything on the host at all.

(Jw123) #8

Thanks @dmaze. I logged into a simple bash shell inside the interactive container using the command below.

docker run -e USER=$USER -e USERID=$UID -v $PWD:$PWD -w=$PWD -p 8889:8889 --rm -it watts/python bash

when I give the id command inside the container, I get the following output -
root@533dab3e1de1:/home/watts/python# id
uid=0(root) gid=0(root) groups=0(root)

When I give the ‘id’ command from the host machine prompt I get the followng result -
uid=1000(watts) gid=1000(watts) groups=1000(watts),4(adm),24(cdrom),27(sudo),30(dip),4

Can this can be fixed somehow?

(David Maze) #9

Probably with --user 1000. When you run id inside the container it won’t say “watts” (the passwd files won’t match) but you’ll have the right numeric user ID. Setting -e USER and -e USERID don’t do anything useful and potentially confuse software and I wouldn’t set them.

(Jw123) #10

Thanks @dmaze. I think I have been able to pinpoint the problem following your suggestion but I don’t have a solution yet. Here’s what I do -

  1. from the host machine I give the following command -
    docker run --user 1000 -v $PWD:$PWD -p 8889:8889 --rm -it watts/python bash
    This logs me into a bash shell in a container as root
  2. Then from inside the container I give following commands -
    a. useradd -m watts -u 1000
    b. chown -R watts /home/watts
    c. groupmod -n watts watts
    d. echo “watts:‘password of watts on host’” | chpasswd
    e. adduser watts sudo && echo ‘%sudo ALL=(ALL) NOPASSWD:ALL’ >> /etc/sudoers
  3. Now while I still donot see the host’s directory listing inside the container, if I open another terminal window on the host machine and without doing ‘eval $(docker-machine env docker2)’ first if I run the same command: (i.e docker run --user 1000 -v $PWD:$PWD -p 8889:8889 --rm -it watts/python bash), I see the directory listing from a bash shell in a new container. But the moment I exit, do ‘eval $(docker-machine env docker2)’ and login again I am no longer able to see the directory listing. Also, when I see the directory listing, I am not able to ping outside the container. I am guessing this is because there was no TLS verification. However, when I don’t see directory listings I can ping an IP outside the container.
    This behaviour is quite consistent and can be repeated multiple times without issues.
    Hence I think this has something to do with TLS. TLS verification is probably blocking the host’s directory listing. I tried
    disabling TLS verification but got the following error when trying to log in: * Are you trying to connect to a TLS-enabled daemon without TLS?

Does this make any easier for you to fix this issue?

Thanks again.

(David Maze) #11

You are doing something wrong. Especially these last two steps aren’t useful (and are dangerous, to the extent that you’re copying your password around): you never “log in” to a container with a password, and if you have root access on the host (which you do) then you never sudo in a container, you just get a root shell in the container and you’re done.

Wait a minute. The screen shot you sent looks a lot like an Ubuntu desktop terminal window. Why are you running Docker Machine at all? It sounds like there’s some missing bit of wiring in getting a directory from your host system to the intermediate VM to Docker, but you don’t need the intermediate VM at all. Just install Docker directly on your host. That might help some of these issues.

If I was going to prod at something more it’d be the VirtualBox file sharing settings but I don’t actually know what I’d be looking for there.

(From the original post it sounded like “uses the local files” was the important part, more so than “runs the Jupyter notebook UI in a prepackaged way”; it looks pretty easy to install Jupyter in a clean Python virtual environment [which has nothing at all to do with a virtual machine and isn’t really that “virtual”] and that might be an easier path towards your real goals.)

(Jw123) #12

Thank v much @dmaze. Its working now.