Multiple Image Tags with Docker Compose
Contents
Recently I answered a question on Stack Overflow
How to use multiple image tags with docker-compose?
The validated answer was based on extends, but it cannot by used anymore in Compose file format 3.x. As suggested by a user, the Extension fields capability added in the version 3.4 of Docker Compose can replace it to achieve the same goal: reuse a single definition to set several tags.
Use YAML extension to define multiple tags
Here is how to use YAML extensions in this case.
version: "3.4"
# Define common behavior
x-ubi-httpd:
&default-ubi-httpd
build: ubi-httpd
# Other settings can also be shared
image: ubi-httpd:latest
# Define one service by wanted tag
services:
# Use the extension as is
ubi-httpd:
*default-ubi-httpd
# Override the image tag
ubi-httpd_major:
<< : *default-ubi-httpd
image: ubi-httpd:1
ubi-httpd_minor:
<< : *default-ubi-httpd
image: ubi-httpd:1.0
# Using an environment variable defined in a .env file for e.g.
ubi-httpd_patch:
<< : *default-ubi-httpd
image: "ubi-httpd:${UBI_HTTPD_PATCH}"
It uses an .env file to define environment variables.
$ cat .env
# ---- UBI HTTP ----- #
UBI_HTTPD_PATCH=1.0.1
Build images
Images can be built now with all the defined tags.
$ docker-compose build
# ...
$ docker images | grep ubi-httpd
# ubi-httpd 1 8cc412411805 3 minutes ago 268MB
# ubi-httpd 1.0 8cc412411805 3 minutes ago 268MB
# ubi-httpd 1.0.1 8cc412411805 3 minutes ago 268MB
# ubi-httpd latest 8cc412411805 3 minutes ago 268MB
Images could also be pushed in the same way.