发布配置与启动脚本
掌握 sys.config 和启动脚本，配置应用环境并控制 Erlang 发布包的精确启动顺序。
发布配置与启动脚本 是 CoddyKit 上的免费 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
What Is Release Configuration?
A release bundles your applications, the Erlang runtime, and configuration. Two files drive runtime behaviour: sys.config for application settings and the boot script for the startup sequence.
The Application Environment
Each OTP application has an environment — a set of key/value parameters. You read them at runtime with application:get_env/2.
application:get_env(my_app, port).sys.config Structure
sys.config is a single Erlang term: a list of {App, [{Key, Value}]} tuples that override application defaults at boot.
[
{my_app, [{port, 8080}, {pool_size, 10}]},
{kernel, [{logger_level, info}]}
].Overriding Defaults
Values in sys.config override those in each app .app file. This lets one codebase run differently per environment (dev, staging, prod) just by swapping config.
Reading Config at Runtime
Inside a gen_server init, pull configured values so behaviour follows the environment.
init([]) ->
{ok, Port} = application:get_env(my_app, port),
{ok, listen(Port)}.What Is a Boot Script?
The boot script (.script compiled to .boot) lists every application and module to load, and the order to start them. The runtime follows it to bring the system up deterministically.
Generated from the .rel File
You describe a release in a .rel file. Tools like systools or rebar3 turn it into the boot script.
{release,
{"my_system", "1.0.0"},
{erts, "13.0"},
[{kernel, "8.0"}, {stdlib, "4.0"}, {my_app, "1.0.0"}]}.Start Phases
Applications start in dependency order. If my_app lists kernel and stdlib as dependencies, the boot script guarantees they start first.
Permanent vs Temporary Apps
In the boot script an application can be permanent (its crash takes down the node), transient, or temporary. Choose permanent for core services.
Layered Config with config/0
You can split configuration across files and merge them, or use runtime os:getenv/1 reads for secrets that should not live in sys.config.
init([]) ->
Url = os:getenv("DATABASE_URL"),
{ok, connect(Url)}.Applying a Custom Config File
At node startup you point to a config file with the -config flag, letting one release run with different settings just by swapping the file.
erl -config /etc/my_system/prod.config -boot my_systemQuick Check
Test your release configuration knowledge.
Recap
You learned how releases are configured and started:
sys.configsets the application environment per deployment- Read values with
application:get_env/2 - The
.relfile is compiled into a boot script - Boot scripts start applications in dependency order
- Use permanent apps for core services and env vars for secrets
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常见问题解答
「发布配置与启动脚本」课时是免费的吗？
是的 — 「发布配置与启动脚本」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程的其余内容，请升级到 CoddyKit PRO。 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程共包含 4 节课。
「发布配置与启动脚本」这节课中我会学到什么？
掌握 sys.config 和启动脚本，配置应用环境并控制 Erlang 发布包的精确启动顺序。 你通过在浏览器中直接运行的动手代码来练习 Erlang OTP: Distributed & Fault-Tolerant Systems Programming，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「发布配置与启动脚本」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课中编写并运行代码吗？
能。每节 Erlang OTP: Distributed & Fault-Tolerant Systems Programming 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。
此课程中的所有课时
- 创建 Erlang 发布包
- 热代码加载与升级
- 发布版本管理与部署
- 发布配置与启动脚本