"docker-compose.yml" version rejected, but why?

Question

My YML file begins like this:

 version: "3.7"
 services:
 ... ... etc ... ...

But I get this error:

 ERROR: Version in "./docker-compose.yml" is unsupported. You might be seeing this [...]

However, the Docker is "Ubuntu's latest version!"

$ docker version
Client:
 Version:           18.09.7
 API version:       1.39
 Go version:        go1.10.1
 Git commit:        2d0083d
 Built:             Fri Aug 16 14:20:06 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server:
 Engine:
  Version:          18.09.7
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.10.1
  Git commit:       2d0083d
  Built:            Wed Aug 14 19:41:23 2019
  OS/Arch:          linux/amd64
  Experimental:     false

$ docker-compose version
docker-compose version 1.17.1, build unknown
docker-py version: 2.5.1
CPython version: 2.7.17
OpenSSL version: OpenSSL 1.1.1  11 Sep 2018

The documentation https://docs.docker.com/compose/compose-file/ says that version 3.7 will work with "18.06.0+" so I really don't understand why I'm getting this message at all. The documentation would suggest that this version of Docker does support (and expect) this version.

Answer 1

It looks like your version of docker-compose is incompatible. The version you are using (1.17.1) only supports a compose file format up to version 3.4. You can view the compatibility matrix in the release notes:

1.17.1 release

You can update docker-compose with the following:

curl -L https://github.com/docker/compose/releases/download/1.25.4/docker-compose-`uname -s`-`uname -m` -o /usr/local/bin/docker-compose
chmod +x /usr/local/bin/docker-compose

And find more information about docker-compose installation here