Nginx uses a few different directives to control system logging. The one included in the core module is called error_log.

error_log directive

Syntax: error_log log_file log_level.

  • log_file: specifies the file where the logs will be written.
  • log_level: specifies the lowest level of logging to be recorded.

Logging levels

  • emerg: emergency situations.
  • alert:
  • crit:
  • error:
  • warn:
  • notice:
  • info
  • debug:

Example:

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error_log /var/log/nginx/error.log crit;

# Don't log anything
error_log /dev/null crit;

error_log is part of the core module; the access_log is part of the HttpLogModule. This provides the ability to customise the log.

log_format directive

The log_format directive is used to describe the format of a log entry using the plain text and variables.

General Syntax:

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log_format format_name string_describing_formatting;

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log_format combined '$remote_addr - $remote_user [$time_local]  '
      '"$request" $status $body_bytes_sent '
      '"$http_referer" "$http_user_agent"';

combined comes predefined with Nginx.

access_log directive

Syntax:

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access_log /path-to-location [ format_of_log buffer_size ];

Specify compression of log file by adding gzip:

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access_log /path-to-log-location format_of_log gzip;

Managing a log rotation

The command that actually rotates the logs is kill -USR1 /var/run/nginx.pid. It sends signal to reload its log files.

Log rotation with logrotate

The logrotate application is used to rotate logs.

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vim /etc/logrotate.d/nginx