Use systemd service overrides instead of systemctl set-env

The latter affects every subsequently started service (at least). The
former only affects the service that needs the env variable.

Author: triarius

packer/linux/conf/bin/bk-install-elastic-stack.sh

@@ -361,8 +361,17 @@ done
 echo "Waited $next_wait_time times for docker to start. We will exit if it still has not started."
 check_docker
 
-# also set in /var/lib/buildkite-agent/cfn-env so that its shown in the job logs
-systemctl set-environment "BUILDKITE_TERMINATE_INSTANCE_AFTER_JOB=${BUILDKITE_TERMINATE_INSTANCE_AFTER_JOB}"
+echo Writing buildkite-agent systemd environment override...
+# also set in /var/lib/buildkite-agent/cfn-env so that it's shown in the job logs
+mkdir -p /etc/systemd/system/buildkite-agent.service.d
+cat <<EOF | tee /etc/systemd/system/buildkite-agent.service.d/environment.conf
+[Service]
+Environment="BUILDKITE_TERMINATE_INSTANCE_AFTER_JOB=${BUILDKITE_TERMINATE_INSTANCE_AFTER_JOB}"
+EOF
+
+echo Reloading systemctl services...
+systemctl daemon-reload
+
 echo Starting buildkite-agent...
 systemctl enable --now buildkite-agent