Lets learn a little about Kernel to know about its error.

Linux Kernel is one of the most important components. If we understand few of its important places where it fits and what it does, we may be able to identify its cause of panic.

When a system boots the GRUB bootloader loads the kernel image (vmlinuz) and the initial RAM disk (initrd or initramfs) from /boot into memory.

Point to be noted: This is one of the 1st places the Kernel may panic if it does not find vmlinuz file in this location.

If this vmlinuz file is corrupted, the Kernel may panic.

Now, lets imagine, here all goes well and kernel was able to load successfully, but kernel has lot of other operations to perform like, it has to mount the “/” (root filesystem). But if the root filesystem is missing or corrupted, the kernel may panic.

Lets say here also all goes smooth, but kernel has the main task is to communicate with all the hardware(RAM, CPU, Disk, network etc) through their drivers, and so kernel has to load all these drivers also, which is called loadable kernel modules(LKM).

Now, here we may find, if a module is corrupted, missing, or incompatible, kernel may panic or If hardware (like RAM or disk) is faulty or unresponsive, the kernel might panic also.

Then the kernel initialises the 1st Linux process called systemd with process id as 1, which in tern starts all the other system services like sshd, ftpd etc and kernel is ready to accept any systemcalls from the processes.

Lets put all these in sequence for better understanding.

Boot Issues

1. Missing or corrupted kernel image (/boot/vmlinuz-*)

2. Incorrect bootloader configuration (wrong GRUB entries, missing initramfs)

3. Corrupt root filesystem (bad sectors on disk, filesystem corruption)

Driver & Module Failures

1. Missing or incompatible kernel modules (modprobe fails)

2. Bad driver updates (Ex: GPU, storage, network drivers)

3. Corrupt initramfs, causing missing essential drivers

Hardware Failures

1. RAM errors (corrupt memory can cause kernel crashes)

2. Disk failures (bad sectors, corrupt partitions)

3. Overheating CPU or power supply issues

Software Bugs & Misconfiguration

1. Kernel bugs or race conditions (bad patches, untested kernel versions)

2. Security violations (SELinux-RHEL, AppArmor-Ubuntu misconfigurations)

3. Invalid system calls (a program forces kernel into an invalid state)

I am sure if we know what are the differennt reasons the Kernel may panic, it becomes very easy to track the issue sequencially.

There are few logs which also may help to identofy:

• journalctl -k
• dmesg
• cat /var/log/syslog | grep -i ‘panic’

There are some quick ways to think when a panic happens, but first need to start with sequencial appraoch as we know now where the kernel may panic.

• Boot into Recovery mode and try to load the older kernel version and see if that helps
• Sometimes reinstall the kernel helps : sudo apt-get install –reinstall linux-image-$(uname -r) && sudo update-grub
• Check if the hardware like RAM or Disk are good 

  • RAM Test: memtest86+ from the GRUB menu

  • Disk Check: smartctl -t long /dev/sda check disk health

I believe this would help to get a starting point, its more complex, but we can start with this and based on different use case, our troubleshooting also changes. But, ultimate goal is to understand the real purpose of Kernel and at which stage what kernel does.

A small example:

Troubleshoot | RHEL-7 Kernel panic error

Before I start to write about this,

let’s understand that kernel panic can be a cause of many different reasons related to the Linux Kernel.

when the kernel tries to load itself to memory, if it finds any difficulties, it provides with some kind of error in the form of Kernel panic. Let’s see how to solve kernel panic error in Linux.

I have even faced other issues related to a kernel panic, but those happened while I was trying to migrate a Linux VM to AWS cloud & that happened because the source Linux had some custom module that was not supported for AWS.

So the migrated instance at AWS gave kernel panic.

So, it’s really difficult to post all the use cases in one blog article. So attempting to start with a simple one first.

Below is an example that I came across in recent days and hence wrote a few lines about my experience on Kernel panic error for a Linux server.

7 Steps to Troubleshoot RHEL-7 Kernel panic error in Linux:

This happens mostly because of initramfs.img file missing or corrupted

1.Boot the system in rescue mode

2.Log in using the root account

3.Navigate to /boot

4. See if initramfs.img file is available (If it is available, it must be corrupted

5.find kernel version (uname -r)
6.mkinitrd initramfs-kernel_version.img kernel_version

7.Boot the machine

Conclusion:

To Troubleshoot kernel crashes or hangs or reboots with kdump and for more Linux server services contact LIA Infraservices the leading Mobile App Development Company in Chennai, Web Development, DevOps, Digital Marketing, Graphics & UI/UX Design, Cloud Migration Services.

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Partho

Partho Das, founder of Lia Infraservices, has 15+ years of expertise in cloud solutions, DevOps, and infrastructure security. He provides consultation on architecture planning, DevOps setup, Kubernetes, and cloud migrations. Partho holds multiple AWS and Azure certifications, along with CISCO CCNA & CCNP.

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