How to configure environment variables for containers in files

1. Set environment variables directly

version: "3"
services:
  web:
    image: my - web - app:v1.0
    environment:
      - DEBUG = false
      - API_KEY = "abcdef123456"

Syntax format：

In the service definition section, you can useenvironmentKeywords to set environment variables.

For example:

Explanation：

Here is a name calledwebservice, it usesmy - web - app:v1.0Mirror.
environmentEach line below defines an environment variable.
DEBUG = falseSet a name calledDEBUGThe Boolean environment variable isfalse，API_KEY = "abcdef123456"Set a name calledAPI_KEYThe string environment variable whose value isabcdef123456。
After the container is started, these environment variables will be read and used by the application in the container. The application can adjust its behavior based on the values of these variables, such asDEBUG = falseTurn off debug mode when .

2. Read environment variables (.env file) from the file

DB_USER = myuser
DB_PASSWORD = mypassword
DB_HOST = database - service
DB_PORT = 3306
DB_NAME = mydatabase

create.envdocument：

existdocker - Create a file in the directory where it is located.envdocument.

For example:

existdocker - References in the file：

version: "3"
services:
  web:
    image: my - web - app:v1.0
    environment:
      - DB_USER = ${DB_USER}
      - DB_PASSWORD = ${DB_PASSWORD}
      - DB_HOST = ${DB_HOST}
      - DB_PORT = ${DB_PORT}
      - DB_NAME = ${DB_NAME}

Explanation：

.envFiles are used to store key-value pairs of environment variables, which makes the management of environment variables more convenient, especially when there are multiple environment variables or the values of environment variables may change frequently.
existdocker - In the file, through${variable name}Form to quote.envEnvironment variables in the file.
For example,DB_USER = ${DB_USER}Will put the container inDB_USERThe value of the environment variable is set to.envIn the fileDB_USERThe value of (here ismyuser）。
In this way, when it is necessary to modify the value of the environment variable, only modify.envFiles, not required indocker - Modify one by one in the file.

3. Use multiple environment files (for different deployment environments)

# 
DEBUG = true
APP_PORT = 3000

# 
DEBUG = false
APP_PORT = 80

Create multiple environment files：

For example, createUsed in the development environment,Used in production environment.

existdocker - Specify the environment file in the file (using--env - fileOptions)：

docker - compose --env - file  up -d
docker - compose --env - file  up -d

This method is started via the command linedocker - composeWhen used.

For example, start in a development environment:

Or start in production:

Explanation：

By specifying different environment files, you can easily switch between different deployment environments (such as development, testing, production).
Each environment file can contain environment variable settings specific to that environment, allowing the application to adjust its behavior according to the environment it is in.
For example, in a development environment, you canDEBUGSet astrueFor easy debugging, set it tofalsefor improved performance and security.

Summarize

The above is personal experience. I hope you can give you a reference and I hope you can support me more.