Syslog-ng prints warning when log rotates
each time syslog rotates, /var/log/messages contains a message like:
Sep 23 01:30:41 turris syslog-ng: WARNING: Configuration file format is too old, syslog-ng is running in compatibility mode. Please update it to use the syslog-ng 3.29 format at your time of convenience. To upgrade the configuration, please review the warnings about incompatible changes printed by syslog-ng, and once completed change the @version header at the top of the configuration file; config-version='3.26'
looks like syslog-ng was upgraded to 3.29 but the config files
were not updated to reflect that.