Troubleshooting Sudden System Restarts on Rocky Linux

Rocky Linux is the recommended operating system for the UMH. However, like any operating system, unexpected system restarts can occur. This guide will walk you through the steps to troubleshoot sudden system restarts on Rocky Linux, helping you identify and resolve potential issues efficiently.

Prerequisites

Before you begin troubleshooting, ensure you have:

• Root or Sudo Access: You'll need administrative privileges to access system logs and crash dumps.
• Basic Knowledge of Linux Commands: Familiarity with the terminal and basic command-line operations.
• Internet Access: For updating packages and seeking additional support if necessary.

Step 1: Verify Reboot History with last reboot

The last command in Linux displays a list of the last logged-in users, system reboots, and shutdowns. Using this command, you can identify when your system was last rebooted.

1.1. Open the Terminal

Access the terminal on your Rocky Linux system. You can do this by searching for "Terminal" in your applications menu or using the keyboard shortcut Ctrl + Alt + T.

1.2. Execute the last reboot Command

Run the following command to view the reboot history:

last reboot

1.3. Interpret the Output

Sample Output:

reboot   system boot  5.14.0-70.el9.x Tue Sep 19 10:15   still running
reboot   system boot  5.14.0-70.el9.x Mon Sep 18 08:45 - 10:15  (01:30)

• system boot: Indicates a system reboot event.
• Kernel Version: 5.14.0-70.el9.x shows the version of the kernel used during the boot.
• Date and Time: Displays when the reboot occurred.
• Duration: Shows how long the system was running before the next reboot.

Action Items:

• Identify Unexpected Reboots: Look for reboots that you did not initiate.
• Correlate with Other Logs: Note the timestamps to cross-reference with system logs for more details.

Step 2: Check for Crash Dumps

Crash dumps provide detailed information about system crashes, including kernel panics, which can help identify the root cause of unexpected restarts.

2.1. Verify if Kdump is Enabled

Kdump is a kernel crash dumping mechanism that captures the contents of the system memory during a crash.

sudo systemctl status kdump

Expected Output:

● kdump.service - Crash recovery kernel arming
   Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; vendor preset: enabled)
   Active: active (exited) since Tue 2024-09-23 09:35:54 UTC; 1 day ago

• Active (exited): Indicates that Kdump is enabled and running.

2.2. Locate Crash Dumps

Crash dumps are typically stored in the /var/crash/ directory.

ls /var/crash/

Possible Output:

2024-09-23-09:35:54/ vmcore

• vmcore: The memory dump file generated during the crash.

2.3. Analyze Crash Dumps

While analyzing crash dumps requires specialized tools and expertise, you can perform basic checks or seek assistance.

Assume you’ve navigated to the crash dump directory and listed the files:

[root@jeremy-flatcar 127.0.0.1-2024-09-23-09:35:37]# ls
kexec-dmesg.log  vmcore  vmcore-dmesg.txt
[root@jeremy-flatcar 127.0.0.1-2024-09-23-09:35:37]#

Steps to Analyze Using vim or nano:

1. View kexec-dmesg.log:This file contains the kernel messages captured during the kexec process, which is used to load the crash kernel.
2. Search for Error Keywords:Once inside the editor, search for common error indicators such as "error," "panic," "oops," or "BUG."
   • In vim: Press /, type your keyword (e.g., /panic), and press Enter.
   • In nano: Press Ctrl + W, type your keyword, and press Enter.
3. Examine vmcore-dmesg.txt:This file contains the dmesg output at the time of the crash, which includes kernel messages and error logs.

Identify Critical Errors:Look for lines indicating kernel panics, oops messages, or specific error codes. For example:

[330990.272768] BUG: unable to handle page fault for address: 0000000000002327
[330990.272793] #PF: supervisor read access in kernel mode
[330990.272815] #PF: error_code(0x0000) - not-present page
...

Using nano:

nano vmcore-dmesg.txt

Using vim:

vim vmcore-dmesg.txt

Using less:

less vmcore-dmesg.txt

Using nano:

nano kexec-dmesg.log

Using vim:

vim kexec-dmesg.log

Using less:

less kexec-dmesg.log

Navigate to the Crash Dump Directory:

cd /var/crash/2024-09-23-09:35:37/

Step 3: Analyze System Logs for Errors

System logs contain valuable information that can help pinpoint the cause of unexpected reboots. Focus on kernel logs and messages leading up to the reboot event.

3.1. Access Previous Boot Logs with journalctl

Use journalctl to view logs from the previous boot session.

sudo journalctl -b -1

• -b -1: Specifies logs from the boot before the current one.

3.2. Filter Logs for Errors and Warnings

Search for common error indicators such as "error," "fail," "panic," or "oops."

sudo journalctl -b -1 | grep -i -E "error|fail|panic|oops"

Sample Output:

Sep 23 09:35:54 jeremy-flatcar kernel: BUG: unable to handle page fault for address: 0000000000002327
Sep 23 09:35:54 jeremy-flatcar kernel: Oops: 0000 [#1] PREEMPT SMP NOPTI
...

3.3. Inspect /var/log/messages

The /var/log/messages file contains a comprehensive log of system activities.

sudo less /var/log/messages

• Navigate and Search: Use / followed by your search term (e.g., /error) to find relevant entries.
• Look for Patterns: Identify recurring errors or warnings that precede the reboot.

Example Search Commands:

Search for Kernel Panics:

/panic

Search for Reboot Messages:

/reboot

Search for Shutdown Messages:

/shutdown

Step 4: Utilize ChatGPT for Log Interpretation

Interpreting complex system logs and crash dumps can be challenging. ChatGPT can assist in analyzing and understanding the data you've collected.

4.1. Preparing Log Data for Analysis

Ensure that you have the relevant log snippets or error messages ready. For example:

[330990.272768] BUG: unable to handle page fault for address: 0000000000002327
[330990.272793] #PF: supervisor read access in kernel mode
[330990.272815] #PF: error_code(0x0000) - not-present page
...

4.2. Using ChatGPT to Interpret Logs

1. Access ChatGPT: Open ChatGPT through your preferred platform.
2. Review the Interpretation:ChatGPT can break down the error messages, explain their significance, and provide potential troubleshooting steps based on the information provided.

Provide Context and Logs:

I encountered the following kernel error on my Rocky Linux system after a sudden reboot:

[330990.272768] BUG: unable to handle page fault for address: 0000000000002327
[330990.272793] #PF: supervisor read access in kernel mode
[330990.272815] #PF: error_code(0x0000) - not-present page
...

Can you help me understand what this means and suggest possible causes?

Summary

Unexpected system restarts on Rocky Linux can disrupt operations and indicate underlying issues. By following this troubleshooting guide, you can:

1. Identify Reboot Events: Use last reboot to verify when reboots occurred.
2. Examine Crash Dumps: Check /var/crash/ for detailed crash information.
3. Analyze System Logs: Utilize journalctl and /var/log/messages to find error patterns.
4. Leverage ChatGPT: Simplify log interpretation and gain actionable insights.

By systematically addressing these areas, you can effectively diagnose and resolve the causes of sudden system restarts, ensuring the stability and reliability of your UMH environment on Rocky Linux.

For further assistance or to report persistent issues, please contact the UMH support team or consult the Rocky Linux Documentation.