/var/log/kern.log: Explanation & Insights

Contains Kernel messages

The /var/log/kern.log is a log file that stores messages generated by the Linux kernel. These messages include system errors, warnings, and important system notifications. The file helps system administrators gain insight into the system's inner workings and troubleshoot when things go wrong.

What Does /var/log/kern.log Contain?

The /var/log/kern.log file contains an array of information, all of which stems from the kernel's activities. The entries in the log file usually include a timestamp, the name of the machine, the kernel component that generated the message, and the message itself. For instance, you might see entries like:

Mar 1 00:01:00 myserver kernel: [ 0.000000] Initializing cgroup subsys cpuset
Mar 1 00:01:00 myserver kernel: [ 0.000000] Initializing cgroup subsys cpu

Why is /var/log/kern.log Important?

The kernel is the heart and soul of a Linux system. So, any messages the kernel generates are crucial for the health and performance of your server. The /var/log/kern.log file allows you to keep track of these messages and diagnose problems like a kernel panic or a hardware network issue.

How to Use /var/log/kern.log?

You can read the /var/log/kern.log file using text editors like nano or vi. However, due to the file's size, it's often more convenient to use tools like tail or grep to filter the kernel messages. For example, to view the last ten lines of the log:

tail -n 10 /var/log/kern.log

Or, to search for error messages:

grep -i error /var/log/kern.log

Problem Diagnosis with /var/log/kern.log

The /var/log/kern.log file is often the first place you should look when you're trying to diagnose a system error. For instance, if your system is facing a high load, you can inspect the kernel log to identify any hardware or software issues, such as a disk I/O error or a memory leak.


In conclusion, the /var/log/kern.log file is a vital tool in the Linux administrator's toolkit. It serves as a window into the kernel's world, allowing you to keep an eye on system operations and troubleshoot problems when needed. So, the next time you face a system issue, remember to check your kernel's diary, the /var/log/kern.log.

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