As traffic increases, Nginx logs grow rapidly, especially in high-traffic or high-frequency access environments. The continuous growth of log files can quickly fill up the server's hard drive. This can not only impact server performance but also prevent applications from recording new logs, and may even cause server crashes. To address this issue, timely detection of abnormal log file growth and the implementation of automated cleanup and optimization solutions are crucial for ensuring the efficient and stable operation of the Nginx server.

　　Identifying the Reasons for Nginx Logs Filling Up the Hard Drive

　　In an Nginx server, log files are typically divided into access logs and error logs. Access logs record all requests entering the server, including the request URL, IP address, response time, etc.; error logs record errors and warnings that occur during server operation. The generation of these log files is closely related to the web application's traffic, Nginx configuration, and log storage methods.

　　The main reasons for Nginx logs filling up the hard drive are usually as follows:

　　**High-Traffic Websites:** For websites with very high traffic, Nginx log files typically grow very quickly, especially if the logs are not effectively rotated or compressed.

　　Inappropriate Log Configuration: Nginx's default logging configuration may record excessive information, such as detailed request parameters and response times, leading to extremely large log files.

　　Incorrect or Unconfigured Log Rotation: If Nginx does not enable log rotation, or the rotation strategy is configured incorrectly (e.g., the rotation period is too long), the log files will continue to grow, consuming a large amount of disk space.

　　Malicious Traffic or Web Scraping Attacks: Certain malicious attacks or web scraping behaviors can cause abnormal request frequencies, resulting in a large amount of log data. Examples include brute-force attacks, DDoS attacks, or high-frequency access from invalid requests.

　　By checking the size of the Nginx log files, you can quickly determine how much disk space the logs are consuming. You can use the following command to check the log file size:

du -sh /var/log/nginx/*

　　This command lists the size of each log file in the Nginx log directory. If a log file's size is close to or exceeds the disk capacity, immediate action is required.

　　Quickly check if Nginx logs are filling up the disk:

　　1. Check log file sizes

　　Use the `du` command to check the size of each log file in the `/var/log/nginx` directory. Nginx access logs are typically located at `/var/log/nginx/access.log`, and error logs are located at `/var/log/nginx/error.log`. If a log file is too large, you can use the `ls -lh` command to check detailed file information.

ls -lh /var/log/nginx/

　　This command will list the detailed size of each file in the Nginx log directory. If the log file size is excessively large, you can pinpoint the root cause of the problem.

　　2. Analyze Log Content

　　Another method is to analyze the contents of the Nginx log files to see if there are any abnormal requests or abnormal traffic. Use the `tail` command to view the latest logs:

tail -n 100 /var/log/nginx/access.log

　　1. Check the most recent 100 records in the log file for abnormal traffic, such as a large number of 404 errors, a large number of duplicate requests, or a large number of requests from a specific IP address. If abnormal traffic is found, further analysis and appropriate defensive measures can be taken.

　　2. Locate the specific log type

　　If Nginx has both access logs and error logs enabled, the problem can be identified by analyzing both log files. If the error log frequently records certain error messages, such as connection timeouts and 404 errors, it indicates that certain requests are causing a large number of log entries, which is one of the reasons for the rapid growth of the log file.

　　3. Check the log rotation configuration

　　If the log file is not effectively rotated, the file size will continue to increase. Check the `/etc/logrotate.d/nginx` configuration file to see if log rotation is configured. If it is not configured or is improperly configured, the logs will continue to grow and consume a large amount of disk space.

　　Check the Nginx log rotation configuration:

cat /etc/logrotate.d/nginx

　　A typical Nginx log rotation configuration is as follows:

/var/log/nginx/*.log {
    daily
    rotate 7
    compress
    delaycompress
    missingok
    notifempty
    create 0640 nginx adm
}

　　This configuration will rotate log files daily, retaining a maximum of 7 old logs and compressing the log files.

　　Solution: Automatically Clean Up Nginx Logs

　　For high-traffic websites, the continuous growth of Nginx log files can quickly fill up disk space. To avoid this, administrators can take the following measures:

　　1. Configure Log Rotation

　　Log rotation is one of the most effective ways to solve the problem of Nginx logs filling up disk space. By configuring `logrotate`, outdated log files can be cleaned up and compressed periodically, preventing individual log files from becoming too large.

　　First, configure the Nginx log rotation strategy in `/etc/logrotate.d/nginx`. You can set it to rotate logs daily, retaining a certain number of historical logs and compressing older logs. For example:

/var/log/nginx/*.log {
    daily
    rotate 30
    compress
    delaycompress
    missingok
    notifempty
    create 0640 nginx adm
}

　　This will ensure daily log rotation and retain 30 days of historical logs; logs older than 30 days will be compressed and archived.

　　2. Regularly Clean Up Log Files

　　In addition to configuring log rotation, you can also write scripts to regularly clean up expired log files. For example, you can write a simple cron job to periodically delete log files older than 30 days:

0 0 * * * find /var/log/nginx/ -name "*.log.*" -mtime +30 -exec rm -f {} \;

　　This command will execute at midnight every day, deleting log files older than 30 days.

　　3. Enable Log Compression

　　Enabling compression is an important optimization step in log rotation configuration. Compressing log files can significantly reduce disk space usage. The logrotate tool compresses rotated logs by default (e.g., using gzip), so enabling compression can effectively slow down disk space consumption.

　　4. Prevent Malicious Traffic from Impacting Log Growth

　　Malicious traffic or crawler attacks can lead to a large number of log entries, so Nginx configuration can be used to limit log generation. For example, use limit_req to limit the request frequency of certain IPs, or use deny and allow rules to restrict access from certain IPs. Additionally, log levels can be configured in nginx.conf to reduce unnecessary logging. For example, setting the log level to error can prevent excessive access logging.

　　5. Use Log Aggregation Tools

　　For high-traffic production environments, relying solely on local Nginx logging and rotation may not be sufficient. Consider using log aggregation tools (such as ELK Stack, Logstash, Fluentd, etc.) to centrally store logs on a remote server or cloud storage. This prevents local hard drives from becoming full of logs while providing powerful log analysis and search capabilities.

　　Nginx logs filling up the hard drive is a common problem in web servers, especially in high-traffic production environments. Properly configuring log rotation, enabling log compression, and regularly cleaning up expired logs can effectively slow down the growth rate of log files, preventing the hard drive from quickly filling up. Meanwhile, enhancing log monitoring, optimizing log configuration, and preventing the impact of malicious traffic are key to solving this problem in the long run. Implementing the above solutions can ensure the stable operation of the Nginx server while improving the efficiency and accuracy of log management.