I am trying to mount a host directory into the docker container so that any updates done on the host is reflected into the docker containers. I couldn't succeed after googling and reading the docker volume links.

Can somebody point me where I am doing wrong. Here is what I did

kishore$ cat Dockerfile


FROM ubuntu:trusty
RUN apt-get update
RUN apt-get -y install git curl vim
CMD ["/bin/bash"]
WORKDIR /test_container
VOLUME ["/test_container"]

kishore$ tree
.
├── Dockerfile
└── main_folder
    ├── tfile1.txt
    ├── tfile2.txt
    ├── tfile3.txt
    └── tfile4.txt


1 directory, 5 files
kishore$ pwd
/Users/kishore/tdock

kishore$ docker build --tag=k3_s3:latest .


Uploading context 7.168 kB
Uploading context
Step 0 : FROM ubuntu:trusty
 ---> 99ec81b80c55
Step 1 : RUN apt-get update
 ---> Using cache
 ---> 1c7282005040
Step 2 : RUN apt-get -y install git curl vim
 ---> Using cache
 ---> aed48634e300
Step 3 : CMD ["/bin/bash"]
 ---> Running in d081b576878d
 ---> 65db8df48595
Step 4 : WORKDIR /test_container
 ---> Running in 5b8d2ccd719d
 ---> 250369b30e1f
Step 5 : VOLUME ["/test_container"]
 ---> Running in 72ca332d9809
 ---> 163deb2b1bc5
Successfully built 163deb2b1bc5
Removing intermediate container b8bfcb071441
Removing intermediate container d081b576878d
Removing intermediate container 5b8d2ccd719d
Removing intermediate container 72ca332d9809
 kishore$ docker run -d -v /Users/kishore/main_folder:/test_container k3_s3:latest c9f9a7e09c54ee1c2cc966f15c963b4af320b5203b8c46689033c1ab8872a0ea  

kishore$ docker run -i -t k3_s3:latest /bin/bash


root@0f17e2313a46:/test_container# ls -al
total 8
drwx------  2 root root 4096 Apr 29 05:15 .
drwxr-xr-x 66 root root 4096 Apr 29 05:15 ..
 root@0f17e2313a46:/test_container# exit exit  

kishore$ docker -v
Docker version 0.9.1, build 867b2a9

Questions, issues facing:

There are a couple ways you can do this. The simplest way to do so is to use the dockerfile ADD command like so:

ADD . /path/inside/docker/container

However, any changes made to this directory on the host after building the dockerfile will not show up in the container. This is because when building a container, docker compresses the directory into a .tar and uploads that context into the container permanently.

The second way to do this is the way you attempted, which is to mount a volume. Due to trying to be as portable as possible you cannot map a host directory to a docker container directory within a dockerfile, because the host directory can change depending on which machine you are running on. To map a host directory to a docker container directory you need to use the -v flag when using docker run like so:

docker run -v /host/directory:/container/directory -other -options image_name command_to_run

2 successive mounts : I guess many posts here might be using two boot2docker , the reason you don't see anything is because you are mounting a directory from boot2docker not from your host. You basically need 2 successive mounts : the first one to mount a directory from your host to your system and the second to mount the new directory from boot2docker to your container like this:

1. mount local system on boot2docker

sudo mount -t vboxsf hostfolder /boot2dockerfolder

2. mount boot2docker file on linux container

docker run -v /boot2dockerfolder:/root/containerfolder -i -t  imagename

then when you ls inside containerfolder you will see the content of your hostfolder

The user of this question was using Docker version 0.9.1, build 867b2a9 , I will give you an answer for docker version >= 17.06.

What you want, keep local directory synchronized within container directory, is accomplished by mounting the volume with type bind . This will bind the source (your system) and the target (at the docker container) directories. It's almost the same as mounting a directory on linux.

According to Docker documentation, the appropriate command to mount is now mount instead of -v . Here's its documentation:

So, to mount the the current directory (source) with /test_container (target) we are going to use:

    docker run -it --mount src="$(pwd)",target=/test_container,type=bind k3_s3

If these mount parameters have spaces you must put quotes around them. When I know they don't, I would use `pwd` instead:

    docker run -it --mount src=`pwd`,target=/test_container,type=bind k3_s3

You will also have to deal with file permission, see this article.