Docker Restart Update Your Docker

That tells docker that we want it to back up the container image named spree-app with the tag latest.

Im not using Docker for Mac for any production workloads, just development environments, but I wanted to go ahead and do the extra work to try and avoid any data corruption.

This completely wipes out any data thats stored in your containers and volumes, so there were some instructions on how to backup and restore your information.

I ran into some problems with those steps, so I thought Id put together a more concise recipe here.

Docker Restart Update Your Docker

For each of those, go ahead and update your docker-compose.yml to also specify an image for each of those.

For example, in my Rails project, I have both a web and worker container that are built from the current directory.

I give both of those the same image name so that docker-compose build knows it only has to build that container image once.

This isnt specifically required for backing up your container images, but it makes life a lot easier.

One such complexity is the full name of each of your containers.

Docker Compose does the hard work of giving each container a unique container name within the Docker engine.

The easiest way to see the full names is by running docker-compose ps.

As you can see from the output above, they are usually formatted as a combination of the current directory name ( cbits-spree-ecom in my case), the service name, and a number which will only be greater than 1 if you have more than one instance of a container running.

This is done differently with newer versions of the docker-compose.yml file format.

Im using version 2 in this example.

If youre using version 3 or greater, youre likely specifying volumes slightly differently.

The pgdata volume is mounted in the db container at varlibpostgresql and the bundle volume is mounted in both the web and worker containers at bundle.

I know its intimidating, but were going to break it down in a minute.

If youve only ever used docker-compose, then youre about to get a peek at all of the complexity that it typically hides from us.

This is the container that we want, because its the one that has access to the data that we want to back up.

Its going to read the contents of our volume and archive them in a tar file inside the backup directory (which is also the current directory outside of the container).

This is what will give us access to the data from outside of the container.

This will also be done by calling a docker command directly; this one being docker save.

Youll need to call this on the images that are being used by your docker-compose.yml file.

You can quickly get a list of all of those by running the docker-compose images command.

Theres not as much going on in this one, but lets make sure that we understand it anyway.

Docker For Mac Restart