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Docker Common Gotchas

Container always runs automatically

Sometimes, when we start the docker service on a Linux machine, or start colima on macOS, it can happen than one or more containers always run automatically (sometimes causing errors saying a given port is already in use, for example). It may happen when we have previously run a container with --restart=allways.

In my case, it was because I had restart: always in docker-compose.yml in one of my projects:

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services:
  db:
    image: postgres:17
    container_name: myproj
    restart: always
    env_file: .env
    ports:
      - "5432:5432"
    volumes:
      - "pg_myproj_db_data:/var/lib/postgresql/data"
      - "./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d"
      - "./dbdumps/:/dbdumps"

One solution is to update the configuration for the container(s) in question.

$ docker container update --restart no

Of course, if we have restart: always in the docker-compose.yml file, it could be applied the next time that container is run depending on other things, like whether we run it with --rm or not. So maybe we’d want to write restart: no in our compose file.

As of docker 28 (in 2025), these are the known values for the restart policy:

References

Docker entrypoint initdb.d shell script error

The Initial Setup

While working on a certain project, we were using PostgreSQL in Docker. The setup was initially done on a Linux machine. We had this folder structure:

$ tree .
.
├── api
│   ├── foo.hs
│   ├── bar.hs
│   └── server.hs
├── docker
│   ├── docker-compose.yml
│   └── docker-entrypoint-initdb.d
│       └── 01.sh
├── main.hs
├── Makefile
└── README.adoc

The file docker-compose.yml, among other things, had this setup for the DB service:

services:
  db:
    image: postgres:16
    container_name: our_container
    restart: always
    env_file: .env
    ports:
      - 5432:5432
    volumes:
      - "db_data:/var/lib/postgresql/data"
      - "./docker-entrypoint-initdb.d:/docker-entrypoint-initdb.d"

The shell script itself basically consisted of some psql commands to add some initial stuff to the server:

#!/bin/bash

psql \
	-v ON_ERROR_STOP=1 \
	--username "$POSTGRES_USER" \
	--dbname admin <<-EOSQL
	CREATE ROLE $PG_DEV_USER \
	WITH \
		CREATEDB REPLICATION \
		LOGIN PASSWORD '$PG_DEV_PASSWORD' \
	VALID UNTIL 'infinity';
EOSQL

psql -v ON_ERROR_STOP=1 \
	--username "$PG_DEV_USER" \
	--dbname admin <<-EOSQL
	CREATE DATABASE ourdb WITH \
			ENCODING='UTF8' \
			OWNER=$PG_DEV_USER \
			LC_CTYPE='en_US.UTF-8' \
			LC_COLLATE='en_US.UTF-8' \
			TEMPLATE=template0 \
			CONNECTION LIMIT=3;
EOSQL

psql -v ON_ERROR_STOP=1 \
	--username "$PG_DEV_USER" \
	--dbname ourdb <<-EOSQL

CREATE TABLE users ( \
	id VARCHAR(32) PRIMARY KEY \
);

INSERT INTO users ( \
		id \
) VALUES \
('yoda'), \
('aayla'), \
('ahsoka');
EOSQL

File not round error

Later, another engineer fetched the code, did some changes do 01.sh tried ran docker compose up inside the docker directory. The command ran, but the container failed to execute 01.sh with a message similar to this one:

cannot execute
file not found

The Solution

The problem ended up being Windows style of newlines, which uses CRLF, causing bash inside the container to fail to run the shell script.

We simply rewrote the file with Linux LF newlines, and then the problem was solved.

ArchLinux on MacOS m2

FROM --platform=linux/x86_64 archlinux:latest
CMD ["echo", "It works!"]
$ docker build --tag hello:latest --file ./Dockerfile1 .
DEPRECATED: The legacy builder is deprecated and will be removed in a future release.
            Install the buildx component to build images with BuildKit:
            https://docs.docker.com/go/buildx/

Sending build context to Docker daemon  73.73kB
Step 1/3 : FROM archlinux:latest
latest: Pulling from library/archlinux
no matching manifest for linux/arm64/v8 in the manifest list entries

We need to specify the platform:

$ docker build --tag hello:latest --file ./Dockerfile1 .

$ docker run hello:latest
WARNING: The requested image's platform (linux/amd64) does not match
the detected host platform (linux/arm64/v8) and no specific platform
was requested
It works!

docker [go-1.23.1]
$ docker run --platform=linux/x86_64 hello:latest
It works!
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