Docker complaining of strange port specification-CodePudding

I'm working on creating an alpine postfix container, using https://www.iops.tech/blog/postfix-in-alpine-docker-container/. I figure as it's under a year old, it should be good. I set it up, with the only difference being it's done in docker-compose instead of the container directly. I did test it as written in the blog (running docker directly), and it seems to work. But when I do a dc up -d postfix using these configs:

  postfix:
    build:
      context: ./docker/postfix
    container_name: postfix
    ports:
      - 8025:25
    environment:
      - POSTFIX_SMTP_HELO_NAME=localhost
      - POSTFIX_MYORIGIN=localhost
      - POSTFIX_MYHOSTNAME=localhost

I get for postfix Cannot create container for service postfix: invalid port specification: "481525".

CodePudding user response：

Change your ports specification to wrap the ports in quotes

    ports:
      - "8025:25"

When mapping ports in the HOST:CONTAINER format, you may experience erroneous results when using a container port lower than 60, because YAML parses numbers in the format xx:yy as a base-60 value. For this reason, we recommend always explicitly specifying your port mappings as strings.

https://docs.docker.com/compose/compose-file/compose-file-v3/#short-syntax-1

I recommend always wrapping literal values in quotes, to be explicit and to be consistent, to try and avoid these gotchas.

Full conversion

This is the command from the article

docker run \
        -d \
        --rm \
        --init \
        --env POSTFIX_SMTP_HELO_NAME=localhost \
        --env=POSTFIX_MYORIGIN=localhost \
        --env=POSTFIX_MYHOSTNAME=localhost \
        --name postfix-alpine \
        -p 8025:25 \
        postfix-alpine:latest

I would translate it to a docker-compose.yml like this:

^{(I haven't tested this)}

version: "3.9"

services:
  postfix:
    image: postfix-alpine:latest
    container_name: postfix-alpine
    build:
      context: "./docker/postfix"
    ports:
      - "8025:25"
    environment:
      POSTFIX_SMTP_HELO_NAME: "localhost"
      POSTFIX_MYORIGIN: "localhost"
      POSTFIX_MYHOSTNAME: "localhost"