CODEWITHSUNDEEP
docker
That Brazilian Guy
That Brazilian Guy

Reputation: 3521

Config files on a docker image shared with multiple containers

I run different instances of a PHP software using Docker. Each instance has its own database container, app container, docker-compose file, etc (no swarm, kubernetes, or orchestration of any kind).

There there are customizations that I have to include on /usr/local/etc/php/conf.d/. I need to alter the contents of a file, and add another file.

This is how I'm currently achieving this on docker-compose:

volumes:
  - "./conf/disable-opcache.ini:/usr/local/etc/php/conf.d/opcache-recommended.ini:z"
  - "./conf/custom.ini:/usr/local/etc/php/conf.d/custom.ini:z"

It works, but forces me to have a copy of both files for every instance of the app. When I want to make changes, I need to replicate them to every instance.

I want to have an easy, portable, replicable way of placing these customizations on multiple instances of these containers.

I have read this answer and what I'm currently doing is basically their option (a), but it has all the drawbacks I mentioned. I can't use option (b) because there's no support on the images I use - at least not for all the custom configs I need; whereas for option (c) I'd need to create a custom derived image for every version/tag of every image we use.

What I tried was creating an image containing only the configuration files, and add that as a volume. It works if the volume is a folder, but then it "overwrites" the original folder and only these 2 custom files are present, whereas I need the other original files on the folder to be present as well.

If I try to use a single file as a volume, it doesn't work.

I'm thinking I could maybe place all the files in a volume in a new image, and then create symlink on the containers to each file. But I'm not sure how I would create those symlinks on the containers.

There's probably a better way to proceed, but I'm unfortunately stuck.

Upvotes: 3

Views: 1185

Answers (1)

Software Engineer
Software Engineer

Reputation: 16120

Maybe ou should try to make use of the swarm configuration service: based on your description I think it will help you move forward.

You can use swarm on a single 'node' (your local machine), and continue to make use of your compose files. Use: docker swarm init to begin.

You add your disable-opcache.ini file to the service like so:

docker config create dopcache disable-opcache.ini

Then use something like this to pass the config to your containers:

docker service create \
   --name myphpapp \
   --config source=dopcache,target=/usr/local/etc/php/conf.d/opcache-recommended.ini,mode=0440 \
   -c my-docker-compose.yml \
   myphpimage:latest \

Upvotes: 1

Related Questions