docker-compose can be considered a wrapper around the docker CLI (in fact it is another implementation in python as said in the comments) in order to gain time and avoid 500 characters-long lines (and also start multiple containers at the same time). It uses a file called docker-compose.yml in order to retrieve parameters.
You can find the reference for the docker-compose file format here.
So basically docker-compose build will read your docker-compose.yml, look for all services containing the build: statement and run a docker build for each one.
Each build can specify a Dockerfile, a context and args to pass to docker.
To conclude with an example docker-compose.yml file:
version: '3.2'
services:
database:
image: mariadb
restart: always
volumes:
- ./.data/sql:/var/lib/mysql
web:
build:
dockerfile: Dockerfile-alpine
context: ./web
ports:
- 8099:80
depends_on:
- database
When calling docker-compose build, only the web target will need an image to be built. The docker build command would look like:
docker build -t web_myproject -f Dockerfile-alpine ./web
What is the difference between `docker-compose build` and `docker build`? - Stack Overflow
Docker Compose: do I need to run docker compose build first?
Docker-compose build and up
I'm really not understanding `docker-compose build`
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docker-compose can be considered a wrapper around the docker CLI (in fact it is another implementation in python as said in the comments) in order to gain time and avoid 500 characters-long lines (and also start multiple containers at the same time). It uses a file called docker-compose.yml in order to retrieve parameters.
You can find the reference for the docker-compose file format here.
So basically docker-compose build will read your docker-compose.yml, look for all services containing the build: statement and run a docker build for each one.
Each build can specify a Dockerfile, a context and args to pass to docker.
To conclude with an example docker-compose.yml file:
version: '3.2'
services:
database:
image: mariadb
restart: always
volumes:
- ./.data/sql:/var/lib/mysql
web:
build:
dockerfile: Dockerfile-alpine
context: ./web
ports:
- 8099:80
depends_on:
- database
When calling docker-compose build, only the web target will need an image to be built. The docker build command would look like:
docker build -t web_myproject -f Dockerfile-alpine ./web
docker-compose build will build the services in the docker-compose.yml file.
https://docs.docker.com/compose/reference/build/
docker build will build the image defined by Dockerfile.
https://docs.docker.com/engine/reference/commandline/build/
I note that the official tutorial, when discussing Compose, doesn't include the preliminary build step:
docker compose build
...it just gets straight on with
docker compose up
But another tutorial I did previously said you have to build before up'ing the Compose file.
Could someone please clarify when it's necessary to run the build command before up?
Thank you.
As of compose 1.24 along with the 18.09 release of docker (you'll need at least that client version on the remote host), you can run docker commands to a remote host over SSH.
# all docker commands in this shell will not talk to the remote host
export DOCKER_HOST=ssh://user@host
# you can verify that with docker info to see which engine you're talking to
docker info
# and now run your docker-compose up command locally to start/stop containers
docker-compose up -d
With previous versions, you could configure TLS certificates to allow specific clients to connect to the docker API over a network connection. See these docs for more details.
Note, if you have host volumes, the variables and paths will be expanded to your laptop directories, but the host mounts will happen on the remote server where those directories may not exist. This is a good situation to switch to named volumes.
Everything you can do with Docker Compose, you can do with plain docker commands.
Depending on how exactly you're interacting with the remote server, your tooling might have native ways to do this. One specific example I'm familiar with is the Ansible docker_container module. If you're already using a tool like Ansible, Chef, or Salt, you can probably use a tool like this to do the same thing your docker-compose.yml file does.
But otherwise there's more or less a direct translation between a docker-compose.yml file
version: '3'
services:
foo:
image: me/foo:20190510.01
ports: ['8080:8080']
and a command line
docker run -d --name foo -p 8080:8080 me/foo:20190510.01
My experience has been that the docker run commands quickly become unwieldy and you want to record them in a file; and once they're in a file, you start to wish they were in a more structured format, even if you need an auxiliary tool to run them; which brings you back to copying around the docker-compose.yml file. I think that's pretty routine. (Something needs to tell the server what to run.)