Log to /var/log/telegraf/telegraf.log on systemd

closes #1243

CHANGELOG.md

@@ -27,6 +27,7 @@ to "stdout".
 - [#1198](https://github.com/influxdata/telegraf/pull/1198): http_response: override request Host header properly
 - [#1230](https://github.com/influxdata/telegraf/issues/1230): Fix Telegraf process hangup due to a single plugin hanging.
 - [#1214](https://github.com/influxdata/telegraf/issues/1214): Use TCP timeout argument in net_response plugin.
+- [#1243](https://github.com/influxdata/telegraf/pull/1243): Logfile not created on systemd.
 
 ## v0.13 [2016-05-11]
 

scripts/telegraf.service

@@ -6,7 +6,9 @@ After=network.target
 [Service]
 EnvironmentFile=-/etc/default/telegraf
 User=telegraf
-ExecStart=/usr/bin/telegraf -config /etc/telegraf/telegraf.conf -config-directory /etc/telegraf/telegraf.d ${TELEGRAF_OPTS}
+Environment='STDOUT=/var/log/telegraf/telegraf.log'
+Environment='STDERR=/var/log/telegraf/telegraf.log'
+ExecStart=/bin/sh -c "/usr/bin/telegraf -config /etc/telegraf/telegraf.conf -config-directory /etc/telegraf/telegraf.d ${TELEGRAF_OPTS} >>${STDOUT} 2>>${STDERR}"
 ExecReload=/bin/kill -HUP $MAINPID
 Restart=on-failure
 KillMode=process