# Docker

Using `httpgd` to display R plots in a Docker container (Linux container) may be easier than the traditional and common method; linking the X11 window system.

## Basic usage

### Build a docker image

See the `vignette("a00_installation")` for details on how to install `httpgd` on Linux.

You can create a Docker image with `httpgd` installed by create a Dockerfile like below.

    FROM r-base:latest

    # Install httpgd and dependent packages.
    RUN apt-get update \
        && apt-get install -y --no-install-recommends \
        libfontconfig1-dev \
        && apt-get autoremove -y && apt-get clean -y && rm -rf /var/lib/apt/lists/* \
        && install2.r --error --skipinstalled --ncpu -1 \
        httpgd \
        && rm -rf /tmp/downloaded_packages

Run the `docker build` command from your shell to build a Docker image.

    docker build . -f Dockerfile -t httpgd:test

### Create a container

When creating a container with the `docker run` command, bind the port to be used by `httpgd` with the `-p` (`--publish`) option.

If you run R in a container with a command like the following, the 8888 port of the container will be bound to the 8888 port of the Docker host.

    docker run --rm -it -p 8888:8888 httpgd:test R

### Start httpgd server

Running the following command in the R console will initialize the graphics device and start the server.

    httpgd::hgd(host = "0.0.0.0", port = 8888)

Then, copy the displayed link in your browser.

If you want to display the link again, execute the `hgd_url()` function as follows.
The hostname can be replaced with any value (e.g. localhost).

    httpgd::hgd_url(host = "localhost")

## Advanced usage

### Set options in Rprofile

By setting options `httpgd.host` and `httpgd.port` in the Rprofile, you can omit setting the arguments when starting the httpgd server by `hgd()`.

For example, if you create a Dockerfile with the following contents, you can build an image with these options already set in the Rprofile.

    FROM r-base:latest

    # Install httpgd and dependent packages.
    RUN apt-get update \
        && apt-get install -y --no-install-recommends \
        libfontconfig1-dev \
        && apt-get autoremove -y && apt-get clean -y && rm -rf /var/lib/apt/lists/* \
        && install2.r --error --skipinstalled --ncpu -1 \
        httpgd \
        && rm -rf /tmp/downloaded_packages

    # Set default values used in the httpgd::hgd() function.
    RUN echo 'options(httpgd.host = "0.0.0.0", httpgd.port = 8888)' >> /etc/R/Rprofile.site

    EXPOSE 8888