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systemd_environment_file.md

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systemd env file

吴翱翔 systemd 系列文章

.service 的三种配置方法

  1. config file in /etc, e.g. /etc/my.cnf(MySQL), /etc/grafana.ini
  2. %i Specifier, e.g. [email protected]
  3. EnvironmentFile and $FOO means FOO in env file

[email protected]

# [email protected] means using /etc/shadowsocks/1080.json as config
$ cat /usr/lib/systemd/system/[email protected]
ExecStart=/usr/bin/ss-local -c /etc/shadowsocks/%i.json

https://unix.stackexchange.com/questions/396978/specifier-resolution-i-and-i-difference
Thus, the behavior for the instance name /etc/path/to/some-conf is:

%i specifier with escaping: -etc-path-to-some-conf
%I specifier without escaping: /etc/path/to/some/conf

prometheus-node-exporter

prometheus-node-exporter 可没有配置文件的概念，例如想改下端口只能通过命令行入参

不过观察其 service 文件发现可以用 $NODE_EXPORTER_ARGS 环境变量指定命令行入参

而 $NODE_EXPORTER_ARGS 的 $ 符号表示取环境变量的值，一般来自 EnvironmentFile 的环境变量文件

$ sudo systemctl cat prometheus-node-exporter
EnvironmentFile=-/etc/conf.d/prometheus-node-exporter
ExecStart=/usr/bin/prometheus-node-exporter $NODE_EXPORTER_ARGS

通过 systemd env file 修改 node-exporter 端口

node-exporter 默认端口是 9100，假设我想修改成 9001

$ cat /etc/conf.d/prometheus-node-exporter 
NODE_EXPORTER_ARGS="--web.listen-address=:9001"
$ sudo systemctl restart prometheus-node-exporter

# check prometheus port change to 9001
$ curl http://localhost:9001/metrics