Prevent unnecessary writes to disk.

The dash signifies that not every log entry is written immediately to the disk. This should be reserved to really important log messages like the auth log.
Most entries in a standard Syslog configuration indeed uses the dash.

Author: racke

manual/install/configure-system-log.md

@@ -36,7 +36,7 @@ Instruction by syslog servers
 
   2. Add following line to syslog.conf:
      ```
-     local1.* /var/log/sympa.log
+     local1.* -/var/log/sympa.log
      ```
 
   3. Reload syslog service.