Master Nginx Access & Error Logs: Config, Custom Formats, Auto Rotation

Nginx logs are essential for statistics and troubleshooting. There are two main logs: access_log (records client requests) and error_log (records errors).

Access logs capture client IP, user‑agent, referer, request time, URL, status code, and other variables. The log_format directive defines the layout of each line.

log_format main '$server_name $remote_addr - $remote_user [$time_local] "$request" '
                '$status $uptream_status $body_bytes_sent "$http_referer" '
                '"$http_user_agent" "$http_x_forwarded_for" '
                '$ssl_protocol $ssl_cipher $upstream_addr $request_time $upstream_response_time';

Common variables include $server_name, $remote_addr, $remote_user, $time_local, $request, $status, $uptream_status, $body_bytes_sent, $http_referer, $http_user_agent, $http_x_forwarded_for, $ssl_protocol, $ssl_cipher, $upstream_addr, $request_time, and $upstream_response_time. The log_format must be placed inside the http block.

The access_log directive specifies the file path, format, buffer size, gzip compression, flush interval, and optional condition.

# Set access log
access_log /var/logs/nginx-access.log;
access_log logs/access.log main;
access_log /var/logs/nginx-access.log buffer=32k gzip flush=1m;
# Disable logging
access_log off;

The error_log directive defines the file path and log level (debug, info, notice, warn, error, crit). The default level is error.

error_log logs/error.log info;
# Disable error logging (writes to /dev/null)
error_log /dev/null;

Log rotation can be automated with a Bash script that copies the current logs to a dated file and truncates the original files, then scheduled via cron to run daily at midnight.

#!/bin/bash
LOGS_PATH=/usr/local/nginx/logs
YESTERDAY=$(date -d "yesterday" +%Y-%m-%d)
cp ${LOGS_PATH}/access.log ${LOGS_PATH}/access_${YESTERDAY}.log && > ${LOGS_PATH}/access.log
cp ${LOGS_PATH}/error.log ${LOGS_PATH}/error_${YESTERDAY}.log && > ${LOGS_PATH}/error.log

Cron entry:

0 0 * * * /usr/local/nginx/logs/NginxLogRotate.sh