Step 1: Accessing Current Kernel Logs

To view current kernel logs, utilize the dmesg command. This command will display messages from the kernel's ring buffer, which is a temporary storage space for messages generated by the system during boot or runtime.

Step 2: Setting Log Level

Kernel logging level can be configured using the /etc/sysctl.conf file. To set the logging level, add or modify the following line:

kernel.printk = 4 4 1 7

The four numbers represent logging priorities: console, default level, minimum level, and temporary level. Adjusting these values can help reduce or increase the amount of logged information.

Step 3: Persisting Log Storage

For persistent storage of kernel logs, it is advisable to use the rsyslog service. Ensure the service is active and running:

systemctl status rsyslog
systemctl start rsyslog

The configuration of rsyslog can be found in the /etc/rsyslog.conf file, where you can set rules for storing logs in specific files.

Analyzing Kernel Logs

Step 1: Reading and Searching Log Files

For analyzing kernel logs stored by the rsyslog system, utilize tools like less, grep, or awk for browsing and searching specific records in log files, typically located in /var/log/.

Step 2: Utilizing Analysis Tools

There are tools like logwatch or klogd that assist in log analysis by aggregating and processing them into more readable reports. logwatch can be installed and configured to provide regular log summaries.

Step 3: Monitoring and Alerting

For active system monitoring and immediate alerts on critical events, tools like Monit or Nagios can be employed. These tools can monitor logs and generate alerts based on predefined thresholds or events.

 

Proper configuration and analysis of kernel logs are crucial for ensuring stable and secure operation of systems on CentOS 7. By monitoring and analyzing these logs, potential issues can be identified and addressed before they cause significant harm to the system. Regular monitoring and maintenance of these logs should be part of everyday IT infrastructure operations.