Extending stock Docksal images

Think contributing first and only then forking

If you find something is missing or can be improved in the stock Docksal Docker images and you believe others would benefit from it too, then go ahead and submit a feature request or a PR for the respective repo. By using customized images you do not break any warranties, however this will make it more difficult to maintain, including seeking support from the community and Docksal maintainers if you run into issues.

There are several way to extend a stock Docksal image:

The latter is the recommended way of extending Docksal images and is covered below.

Configuration: Dockerfile

  • Create a Dockerfile in .docksal/services/<service-name>/Dockerfile
  • If you have additional local files (e.g., configs) used during the build, put them in the same folder
  • Use an official Docksal image as a starting point in FROM
  • Add customizations (read official Docker docs on working with Dockerfiles and best practices )

Below is an example of extending the cli image with additional configs, apt and npm packages:

.docksal/services/cli/Dockerfile

# Use a stock Docksal image as the base
FROM docksal/cli:2.2-php7.1

# Install addtional apt packages
RUN apt-get update && apt-get -y --no-install-recommends install \
    netcat-openbsd \
    # Cleanup
    && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

# Copy additional config files
COPY ssh.conf /opt/cli/ssh.conf

# Inject additional SSH settings
RUN \
    cat /opt/cli/ssh.conf >> /home/docker/.ssh/config && \
    cat /home/docker/.ssh/config

# All further commands will be performed as the docker user.
USER docker

# Install additional global npm dependencies
RUN \
    # Initialize nvm environment
    . $NVM_DIR/nvm.sh && \
    # Install node packages
    npm install -g node-sass

# IMPORTANT! Switching back to the root user as the last instruction.
USER root

Here's another example for web:

# Use a stock Docksal image as the base
FROM docksal/web:2.1-apache2.4

RUN set -x \
    # Enabled extra modules
    && sed -i '/^#.* expires_module /s/^#//' /usr/local/apache2/conf/httpd.conf

Configuration: docksal.yml

If using default Docksal stacks (no docksal.yml in the project repo), create a .docksal/docksal.yml file in the repo with the following content:

version: "2.1"

services:
  <service-name>:
    image: ${COMPOSE_PROJECT_NAME_SAFE}_<service-name>
    build: ${PROJECT_ROOT}/.docksal/services/<service-name>

Replace <service-name> with the actual service name you are extending, e.g., cli.

If there is already a custom docksal.yml file in the project repo, then make the corresponding changes in it as shown above. Note: The existing image attribute should be replaced.

Following the previous example, here's what it would look like for cli:

  cli:
    ...
    image: ${COMPOSE_PROJECT_NAME_SAFE}_cli
    build: ${PROJECT_ROOT}/.docksal/services/cli
    ...

Building

Building a customized image happens automatically with fin project start. The built image will be stored locally and used as the service image from there on.

Additionally, fin build command is a proxy command to docker-compose build and can be used for more advanced building scenarios.

Note: it might seems like image is being rebuilt every time project starts, but it really isn't.

There is no way for Docksal to know if your built image is the latest. Even if we checked for Dockerfile changes that would not be enough, because Dockerfile can use some other files that can change. Therefore the best Docksal option is to run docker-compose build every time.

docker-compose build launches docker which knows what files changed and can compare things. If docker sees no changes then it does not actually rebuild image. You see output in the console, but there are no real changes made to images (and output in the console actually says exactly that). That output is basically just a check if nothing has changed. There is no good way to silence that output as in case there was some error the output would render very useful.