Chapter 38. Installing and updating the Kernel

The kernel is a core part of a Linux operating system that manages the system resources, and provides the interface between hardware and software applications. The Red Hat kernel is a custom-built kernel based on the upstream Linux mainline kernel that Red Hat engineers further develop and harden with a focus on stability and compatibility with the latest technologies and hardware.

This section describes how to install, update, and select a kernel in the GRUB boot loader.

38.1. Installing the kernel

The following procedure describes how to install new kernels using the yum package manager.

Procedure

  • To install a specific kernel version, use the following:

    # yum install kernel-{version}

Additional resources

38.2. Updating the kernel

The following procedure describes how to update the kernel using the yum package manager.

Procedure

  1. To update the kernel, use the following:

    # yum update kernel

    This command updates the kernel along with all dependencies to the latest available version.

  2. Reboot your system for the changes to take effect.
Note

When upgrading from Red Hat Enterprise Linux 7 to Red Hat Enterprise Linux 8, follow relevant sections of the Upgrading from RHEL 7 to RHEL 8 document.

38.3. Starting RHEL using a previous kernel version

By default, after you update, the system boots the latest version of the kernel. Red Hat Enterprise Linux allows to have three kernel versions installed at the same time. This is defined in the /etc/dnf/dnf.conf file (installonly_limit=3).

If you observe any issues when the system is loaded with the new kernel, you can reboot it with the previous kernel and restore the production machine. Contact support for troubleshooting the issue.

Procedure

  1. Start the system.
  2. In the GRUB boot loader, you see the installed kernels. Use the and keys to select a kernel, and press Enter to boot it.