os/docs/os/system-services/environment/index.md

title	layout
Environment	os-default

Environment

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The environment key can be used to customize system services. When a value is not assigned, RancherOS looks up the value from the rancher.environment key.

In the example below, ETCD_DISCOVERY will be set to https://discovery.etcd.io/d1cd18f5ee1c1e2223aed6a1734719f7 for the etcd service.

rancher:
  environment:
    ETCD_DISCOVERY: https://discovery.etcd.io/d1cd18f5ee1c1e2223aed6a1734719f7
  services:
    etcd:
      ...
      environment:
      - ETCD_DISCOVERY

Wildcard globbing is also supported. In the example below, ETCD_DISCOVERY will be set as in the previous example, along with any other environment variables beginning with ETCD_.

rancher:
  environment:
    ETCD_DISCOVERY: https://discovery.etcd.io/d1cd18f5ee1c1e2223aed6a1734719f7
  services:
    etcd:
      ...
      environment:
      - ETCD_*