Document disable-syslog intereaction with systemd

See #4713 for context

diff --git a/docs/markdown/authoritative/running.md b/docs/markdown/authoritative/running.md
index d3bae4769f0622a873162ca82dcb74eb358488f6..65201ca8e8a64f491b4b88d465d6a5306361bad6 100644 (file)
--- a/docs/markdown/authoritative/running.md
+++ b/docs/markdown/authoritative/running.md
@@ -20,6 +20,11 @@ interpreted by the guardian, which causes the guardian to sever the connection
 to the inner process and terminate it, after which it terminates itself. Requests
 that require data from the actual nameserver are passed to the inner process as well.
 
+## Logging to syslog on systemd-based operating systems
+By default, logging to syslog is disabled in the the systemd unit file to prevent the service logging twice, as the systemd journal picks up the output from the process itself.
+
+Removing the `--disable-syslog` option from the `ExecStart` line using `systemctl edit --full pdns` enables logging to syslog.
+
 # Controlling A Running PowerDNS Server
 As a DNS server is critical infrastructure, downtimes should be avoided as much
 as possible. Even though PowerDNS (re)starts very fast, it offers a way to