ERROR RollingFileAppender

When I check the service unifi status I see this error and would like to clear it up. I am noob+ in Ubuntu so I can figure things out if given clear instructions on where to start looking and how to look. If anyone can help I would greatly appreciate it.

ERROR Unable to invoke factory method in class org.apache.logging.log4j.core.appender.
RollingFileAppender for element RollingFile: java.lang.
IllegalStateException: No factory method found for class org.apache.logging.log4j.core.appender.
RollingFileAppender java.lang.IllegalStateException: No factory method found for class org.apache.logging.log4j.core.appender.
RollingFileAppender

This is usually a write permissions issue, where the service is not permitted to write to the logging location.

In your log4j.xml file you'll see sections that look like this:

<RollingFile
    name="RollingFile"
    fileName="${log.dir}/le-${app}.log"
    filePattern="${log.dir}/le-${app}-%d{yyyy-MM-dd}-%i.log.gz"
    ignoreExceptions="false"
    ...
</RollingFile>

Note the {log.dir} location and confirm that the service running Unifi is able to write to that directory. If it cannot, consider creating a specific directory for the service to use like this:

sudo mkdir /var/log/unifi
sudo chown -R {unifi}:{unifi} /var/log/unifi 

^{Note: Be sure to change {unifi} to whatever username is running the service.}

The location does not need to be within /var/log if you would rather the logs be written somewhere else.