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Linux:Panic

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Goutam Kumar
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3 min read

Several time after patching we will get KPE(Kernel Panic Error)

Understanding Linux Kernel Panic: A kernel panic occurs when the Linux kernel encounters a critical error that it cannot recover from. This results in the system halting, displaying diagnostic information on the screen, and leaving the user in a state of uncertainty. To comprehend kernel panics better, it's essential to understand the steps involved in the Linux boot process.

  1. BIOS/UEFI Initialization: The boot process begins with the Basic Input/Output System (BIOS) or Unified Extensible Firmware Interface (UEFI) initializing hardware components and performing a Power-On Self-Test (POST). This phase ensures that the hardware is in a stable state before handing over control to the bootloader.

  2. Bootloader Execution: The bootloader, often GRUB (GRand Unified Bootloader) or LILO (LInux LOader), is responsible for loading the Linux kernel into memory. It also allows users to choose the desired kernel or operating system to boot.

  3. Kernel Initialization: Once the bootloader hands control to the kernel, the Linux kernel initializes essential components, mounts the root file system, and sets up key data structures. Any failure at this stage can trigger a kernel panic.

  4. Init Process: The kernel then starts the init process, which is responsible for initializing user-space and managing system services. Init spawns other processes, setting the stage for the user to interact with the system.

Resolving Linux Kernel Panic with a Rescue Image: When a kernel panic occurs, it's crucial to have a plan for recovery. A rescue image is a minimalist Linux environment designed for troubleshooting and fixing issues. Here's how you can use a rescue image to resolve a kernel panic:

  1. Boot from the Rescue Image:Create a bootable USB or CD/DVD with a rescue image (e.g., a LiveCD or a specialized rescue distribution like SystemRescueCd).Boot your system from the rescue image, ensuring that it mounts the root file system.

  2. Mount the Root File System:Identify and mount your Linux root file system from the rescue environment.

  3. Chroot into the System:Change the root directory to your mounted file system using the chroot command. This makes the rescue environment the new root for the commands you execute.

  4. Diagnose and Fix the Issue:Identify the cause of the kernel panic by examining logs, configuration files, and other system information. Make necessary repairs, such as reinstalling a corrupted kernel, updating drivers, or fixing configuration errors.

  5. Update Bootloader Configuration:Ensure that the bootloader configuration points to the correct kernel and initramfs images.

  6. Reboot:Exit the chroot environment, unmount the file systems, and reboot your system.

  7. Troubleshooting:(Re building of initramfs.img-->point to vmlinuz because kernel is present in the hardisk & vmlinuz is used during the booting)

1.Boot the system in rescue mode

2.Log in using the root account

3.Navigate to /boot .i.e. cd /boot after that <ll> command

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

5.Go to the details you must find that file is not present and generate the initramfs.img file

6. uname -r(know the kernel release)

dracut -f initramfs-<kernal release no>.img <kernal release no>

(--force/-f for force mode) or

mkinitrd --force initramfs-<kernal release no>.img <kernel release no>

Reboot the system