ProFTPD Logging: Log Levels

Log Levels As mentioned in the logging documentation, log messages are logged at different log levels (also known as log priorities), and with different facilities (i.e. the component generating the log message).

The following table lists the supported log levels, in descending priority order. Thus the DEBUG level has the lowest priority, and the EMERG level has the highest priority.

 Level   Description 
 EMERG   Fatal/unrecoverable error/condition, application is unusable and stops immediately 
 ALERT   Condition requires immediate intervention by administrator/operator 
 CRIT   Condition should be corrected immediately, but indicates e.g. failure in secondary system/library 
 ERR   Non-urgent failure conditions that should be relayed to developers and/or administrators; should be resolved/corrected soon 
 WARNING   Unexpected error/condition that may require intervention to review/correct 
 NOTICE   Significant/noteworthy condition, no intervention/action required 
 INFO   Normal operating conditions, no intervention/action required 
 DEBUG   Internal details of application operations useful to developers, not necessarily useful during normal operations 

The proftpd daemon can use any or all of the above log levels for its emitted log messages, depending on the situation. You might find that you only want proftpd to log messages above a certain level; for example, you might not be interested in INFO and DEBUG level messages. ProFTPD logs all levels by default. To tell proftpd to silently ignore all log messages below a certain level, use the SyslogLevel directive. Thus to ignore INFO/DEBUG messages, you would use:

  SyslogLevel notice

Note that additional log filtering is also done by the syslogd daemon, to which proftpd logs by default. You will need to consult your syslogd configuration (typically found in /etc/syslog.conf) to see whether it is capturing log messages from the facility used by proftpd (default is "daemon"), and whether it is filtering out messages below a certain level/priority.

If you need to tell proftpd to use a different facility, so that it matches your /etc/syslog.conf settings for example, you can use the SyslogFacility directive like so:

  # Tell proftpd to log using the "ftp" facility, rather than "daemon"
  SyslogFacility ftp

The DEBUG Level
ProFTPD treats the DEBUG log level a little differently. There are so many conditions which are relevant only when triaging a specific issue (such as figuring out why a user cannot log in, or why a file cannot be uploaded) that the DEBUG level would become cluttered. Additional filtering of these debug messages is needed. Thus ProFTPD imposes its own notion of debug levels within the DEBUG logging level/priority.

The DebugLevel directive is used to control the granularity/verbosity of the DEBUG level messages; the default level is 0, and goes to 10 (inclusive). In general, the higher the DebugLevel, the more debug messages will be emitted by proftpd to the DEBUG logging level/priority.

Additional Logging
Note that ProFTPD also supports even finer-grained logging of intervals via its
trace logging. Trace logging, however, is completely unrelated to syslogd, and thus the syslog facility and level concepts/filtering do not apply to trace logging.

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