Parece que você pode definir variáveis de ambiente dentro de um arquivo de unidade do systemd ...
Por sugestão dos comentadores, aqui está a solução:
Using environment variables in systemd units
Environment directive
systemd has an Environment directive which sets environment variables for executed processes. It takes a space-separated list of variable assignments. This option may be specified more than once in which case all listed variables will be set. If the same variable is set twice, the later setting will override the earlier setting. If the empty string is assigned to this option, the list of environment variables is reset, all prior assignments have no effect. Environments directives are used in built-in Container Linux systemd units, for example in etcd2 and flannel.
With the example below, you can configure your etcd2 daemon to use encryption. Just create /etc/systemd/system/etcd2.service.d/30-certificates.conf
drop-in for etcd2.service:
[Service]
# Client Env Vars
Environment=ETCD_CA_FILE=/path/to/CA.pem
Environment=ETCD_CERT_FILE=/path/to/server.crt
Environment=ETCD_KEY_FILE=/path/to/server.key
# Peer Env Vars
Environment=ETCD_PEER_CA_FILE=/path/to/CA.pem
Environment=ETCD_PEER_CERT_FILE=/path/to/peers.crt
Environment=ETCD_PEER_KEY_FILE=/path/to/peers.key
Then run sudo systemctl daemon-reload
and sudo systemctl restart etcd2.service
to apply new environments to etcd2 daemon.
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