Bob Learns Kernel Management on AlmaLinux

Bob’s next challenge was to understand and manage the Linux kernel, the core of the operating system. From loading kernel modules to upgrading the kernel itself, mastering kernel management would give Bob greater control over his AlmaLinux server’s performance and functionality.

“The kernel is the heart of my system—time to keep it beating smoothly!” Bob said, eager to dive into the depths of kernel management.

Chapter Outline: “Bob Learns Kernel Management on AlmaLinux”

1. Introduction: What Is the Linux Kernel?

   • Overview of the kernel and its role in the system.
   • Key components: modules, drivers, and configuration files.

2. Viewing and Managing Kernel Information

   • Checking the current kernel version.
   • Exploring /proc and /sys.

3. Managing Kernel Modules

   • Loading and unloading modules with modprobe.
   • Viewing active modules with lsmod.
   • Writing custom module configurations.

4. Upgrading the Kernel on AlmaLinux

   • Checking for available kernel updates.
   • Installing and switching between kernel versions.

5. Troubleshooting Kernel Issues

   • Diagnosing boot problems with dmesg and journalctl.
   • Recovering from kernel panics.

6. Conclusion: Bob Reflects on Kernel Mastery

Part 1: Introduction: What Is the Linux Kernel?

Bob learned that the Linux kernel is the bridge between hardware and software. It manages resources like memory, CPU, and devices, and provides an interface for applications to interact with the hardware.

Key Concepts

• Kernel Modules: Extend kernel functionality dynamically, such as device drivers.
• Configuration Files: Files like /etc/sysctl.conf influence kernel behavior.

“Understanding the kernel is like opening the hood of my Linux car!” Bob said.

Part 2: Viewing and Managing Kernel Information

Step 1: Checking the Current Kernel Version

• Bob checked the current kernel version:

  uname -r
  

  Example output:

  4.18.0-425.13.1.el8.x86_64
  

Step 2: Exploring Kernel Parameters

• View runtime kernel parameters in /proc/sys:

  ls /proc/sys
  

• Check a specific parameter, like network settings:

  cat /proc/sys/net/ipv4/ip_forward
  

• Modify parameters temporarily:

  echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
  

Step 3: Persistent Kernel Configuration

• Bob made the change permanent in /etc/sysctl.conf:

  net.ipv4.ip_forward = 1
  

  • Apply the changes:

    sudo sysctl -p
    

“Kernel parameters are like system dials—I can tune them as needed!” Bob said.

Part 3: Managing Kernel Modules

Step 1: Listing Loaded Modules

Bob checked which kernel modules were currently loaded:

lsmod

Example output:

Module                  Size  Used by
xfs                   958464  1
ext4                  778240  2

Step 2: Loading and Unloading Modules

• Load a module:

  sudo modprobe <module_name>
  

  Example:

  sudo modprobe vfat
  

• Unload a module:

  sudo modprobe -r <module_name>
  

Step 3: Writing Persistent Module Configurations

Bob needed to load the vfat module automatically at boot:

• Edit the /etc/modules-load.d/custom-modules.conf file:

  vfat
  

“Modules make the kernel flexible—it’s like plugging in extra features!” Bob said.

Part 4: Upgrading the Kernel on AlmaLinux

Step 1: Checking for Available Kernel Updates

Bob checked if new kernel versions were available:

sudo dnf check-update kernel

Step 2: Installing a New Kernel

• Install the latest kernel:

  sudo dnf install kernel
  

Step 3: Switching Between Kernel Versions

• List available kernels:

  sudo awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg
  

• Update GRUB to boot into a specific kernel:

  sudo grub2-set-default "CentOS Linux (4.18.0-425.13.1.el8.x86_64)"
  sudo grub2-mkconfig -o /boot/grub2/grub.cfg
  

• Reboot to apply changes:

  sudo reboot
  

“Upgrading the kernel is like giving my server a software heart transplant!” Bob joked.

Part 5: Troubleshooting Kernel Issues

Step 1: Diagnosing Boot Problems

• View the kernel ring buffer with dmesg:

  dmesg | less
  

• Check system logs for errors:

  sudo journalctl -k
  

Step 2: Recovering from Kernel Panics

If the server failed to boot, Bob used the GRUB menu to select an older kernel.

• Modify GRUB during boot:
  1. Press e at the GRUB menu.
  2. Edit the kernel line to boot into recovery mode.
  3. Press Ctrl+x to boot.

Step 3: Restoring a Default Kernel

If an upgrade caused issues, Bob reverted to the default kernel:

sudo dnf remove kernel
sudo grub2-set-default 0

“With these tools, even kernel panics don’t scare me!” Bob said.

Conclusion: Bob Reflects on Kernel Mastery

By learning kernel management, Bob could now troubleshoot hardware issues, optimize performance, and ensure his AlmaLinux server stayed secure and up to date.

Next, Bob plans to explore Configuring DNS Services with BIND on AlmaLinux.