Oracle unbreakable linux kernel

Manage the Boot Kernel for Oracle Linux 8

Introduction

This tutorial describes how to set the default kernel of an Oracle Linux system from the command line. This tutorial is targeted at Oracle Linux 8 users, but the grubby command is also available on Oracle Linux 6 and Oracle Linux 7.

Background

By default, Oracle Linux systems are configured to boot the most recent kernel version first. In most cases, changing the default kernel is unnecessary.

However, the default kernel might not be the correct version to use in certain scenarios, such as the following:

• The current kernel version might be incompatible with a particular hardware you are using.
• Cases involving Unbreakable Enterprise Kernel (UEK) releases on the system
• UEK releases are typically based on kernel versions that are newer than the Red Hat Compatible Kernel (RHCK) version on which an Oracle Linux release is based. Thus, the new UEK version becomes the default kernel, which is not the same as the Oracle Linux kernel.
• If a UEK beta or technical preview release is installed on the system, the UEK kernel needs to be demoted to ensure that the kernel is used only if intentionally and manually selected as the boot kernel by an administrator.
• A UEK kernel might need to be promoted because a specific software depends on it.

These examples and other similar cases would necessitate that you switch between kernel types.

In previous releases, setting the default kernel was performed by configuring the GRUB boot loader or by using other alternative commands. Now, however, you should preferrably use the grubby command to control and manage all of your boot requirements. This tool offers the benefit of being scriptable and can abstract bootloader configuration from the user.

Objectives

In this lab, you’ll learn how to:

• determine the current loaded kernel
• determine the default kernel
• determine which kernel versions are available on the system
• how to use grubby to manage kernels

What Do You Need?

• Any Oracle Linux system that has the grubby package installed

(Hands-on Lab) Connect to the Compute Instance

Note: This step is specific to the Oracle provided free lab environment.

The Desktop environment will display before the instance(s) are ready. Deployment of this environment can take two to five minutes, depending on the number of resources and provisioning steps needed.

First, to access the lab compute instance(s), connect to the Oracle Cloud Console and copy the compute instance Public IP address.

1. Sign in to Oracle Cloud Console, and select your Compartment.
2. Click Instances.

Copy the Public IP to a temporary location (such as a text file) on your computer.

To copy, highlight the IP address with the mouse and press Ctrl+C.

Connect to the instance.

Where is the IP address copied from the Oracle Cloud Console.

Accept the ECDSA key fingerprint by typing yes at the prompt.

You are now connected to the compute instance for this lab.

If the connection fails with the Permission denied (publickey,gssapi-keyex,gssapi-with-mic) message, wait a bit longer for the provisioning process to complete and try making the ssh connection again.

Check available kernels

Several methods are available for checking which kernels are available on a system.

Using the rpm command

Note that the command output also includes other kernel related packages and can therefore be confusing.

Listing the kernels in the /boot directory

The command produces an accurate list of kernels available on the system. However, due to the way kernels are named, the kernel version that the system currently uses is not easily identifiable.

Using the grubby command on specific kernels or using the ALL option:

The command provides fuller information about the boot configuration associated with each kernel in the system’s /boot directory. The details are based on the GRUB title configuration.

In general, kernels are named to include the upstream version number and the distribution build numbering. The kernel names on Oracle Linux also include indications of whether or not they are standard RHCK or whether they are UEK based. Additionally, the names also identify their system architecture. For example, the el8 suffix would indicate an RHCK, while el8uek would indicate a UEK.

Check the current default kernel

To check which kernel is already configured as the current default kernel to use at boot, run:

To check which kernel is currently running on a system, run:

If the default kernel and the currently running kernel are not identical, the underlying reasons might be one of the following:

• A newer kernel is installed, but the system has not been rebooted.
• During a system reboot, an alternative kernel was manually selected to be the operative kernel.
• The default kernel was manually updated but the system has not been rebooted after the update.

Change the default kernel

To switch to a different default kernel, run the following command. Make sure to specify the full path to the designated default kernel.

The change takes effect immediately and persists across system reboots.

The grubby command has additional boot arguments for configuring kernel and boot operations. Refer to the documentation for more information.

Change kernel command line boot parameters

Use the —update-kernel option to update a kenel entry in combination with —args to add new arguments or —remove-arguments to remove existing arguments. Multiple arguments can be specified for each option in a quoted space-separated list. You can add and remove arguments in the same operation.

To update a specific kernel, provide the —update-kernel option with the full path to the kernel that you wish to update. To update all kernel entries to use a specific kernel boot argument, you can set —update-kernel=ALL .

For the purpose of this tutorial you can update all kernel entries to change the loglevel and LANG arguments:

Use the grubby info=ALL command to check that the change is implemented across kernels:

Video Demonstrations

An introductory video that provides an overview of the kernel and underlying system architecture and which demonstrates switching kernel using the grubby command is provided at https://www.youtube.com/watch?v=a0zXGhzPRp8.

A more advanced video demonstration and tutorial is provided at https://www.youtube.com/watch?v=0dv87RFGcKI if you need more information on working with GRUB2 on Oracle Linux 8.

Note that this tutorial does not describe use of the grubby command and explains the underlying components that grubby interacts with. For most kernel management requirements on Oracle Linux, the grubby tool is sufficient.

Additional Information

More Learning Resources

Explore other labs on docs.oracle.com/learn or access more free learning content on the Oracle Learning YouTube channel. Additionally, visit education.oracle.com/learning-explorer to become an Oracle Learning Explorer.

For product documentation, visit Oracle Help Center.

Manage the Boot Kernel for Oracle Linux 8

Copyright © 2021, Oracle and/or its affiliates.

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Oracle unbreakable linux kernel

The Unbreakable Enterprise Kernel for Oracle Linux provides the latest innovations from upstream development to customers who run Oracle Linux in the data center.

The Unbreakable Enterprise Kernel is included and enabled by default in Oracle Linux kernels. It is based on a recent stable mainline development Linux kernel, and also includes optimizations developed in collaboration with Oracle Database, Oracle middleware, and Oracle hardware engineering teams to ensure stability and optimal performance for the most demanding enterprise workloads.

Oracle highly recommends deploying the Unbreakable Enterprise Kernel in your Oracle Linux environment, especially if you run enterprise applications. However, using Unbreakable Enterprise Kernel is optional. If you require strict Red Hat Enterprise Linux (RHEL) kernel compatibility, then Oracle Linux also includes a kernel compatible with the RHEL Linux kernel, compiled directly from the RHEL source code.

You can obtain more information about the Unbreakable Enterprise Kernel for Oracle Linux at the following URL:

The Unbreakable Enterprise Kernel for Oracle Linux is the standard kernel used with Oracle products. The build and QA systems for Oracle Database and other Oracle products use the Unbreakable Enterprise Kernel for Oracle Linux exclusively. The Unbreakable Enterprise Kernel for Oracle Linux is also the kernel used in Oracle Exadata and Oracle Exalogic systems. Unbreakable Enterprise Kernel for Oracle Linux is used in all benchmark tests on Linux in which Oracle participates, as well as in the Oracle Database Preinstallation RPM program for x86-64.

Oracle Ksplice, which is part of Oracle Linux, updates the Linux operating system (OS) kernel, while it is running, without requiring restarts or any interruption. Ksplice is available only with Oracle Linux.

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Unbreakable Enterprise Kernel for Oracle Linux

The Unbreakable Enterprise Kernel (UEK), included as part of Oracle Linux, provides the latest open source innovations, key optimizations and security for enterprise cloud workloads. This Linux kernel powers Oracle Cloud and Oracle Engineered Systems such as Oracle Exadata Database Machine. Oracle tests UEK intensively with demanding Oracle workloads, and recommends UEK for Oracle deployments and all other enterprise deployments.

Oracle contributes to upstream Linux kernel development with enhancements that benefit Oracle Database, middleware, applications and hardware, as well as our broad partner ecosystem. These enhancements are distributed to customers through UEK for Oracle Linux.

By selectively integrating the latest open source Linux capabilities into UEK while still providing application binary compatibility with the Red Hat Compatible Kernel, Oracle makes it easy to run the most demanding cloud and enterprise workloads without compromising stability and security. We test all our on-premises software, and run Oracle Cloud on UEK, ensuring you can achieve the highest scalability and performance with your current workloads and those of the future.

FEATURES	BENEFITS
DTrace	DTrace provides Oracle Linux customers with a comprehensive, dynamic tracing framework. Find and fix performance and stability problems easily and securely with DTrace enhancements like perf_events as Statically Defined Trace (SDT) probes.
Performance and Scalability Improvements	Notable performance improvements include: Improvements and fixes to NUMA balancing help resolve issues that could cause high I/O wait times when this feature was enabled. NUMA balancing is automatically enabled on systems that have multiple NUMA nodes. RDMA over Converged Ethernet (RoCE), a standard InfiniBand Trade Association (IBTA) protocol enables efficient data transfer for RDMA over Ethernet networks using UDP encapsulation to transcend Layer 3 networks. TCP-BBR, a feature that can be used to achieve higher bandwidth and lower latency for internet traffic can offer significant performance improvements for internet-based applications. BBR (Bottleneck Bandwidth and Round-Trip Time) is a scheduling algorithm that helps to control the transmit rate of the TCP protocol to reduce buffering by monitoring round-trip times against bandwidth bottlenecks to reduce TCP congestion.
Btrfs Improvements	Continued improvements in scalability, performance and stability for Btrfs are key features of this latest release.
Virtualization Improvements	Significant improvements to KVM functionality including: Secure Encrypted Virtualization (SEV) for AMD-V enabled. AMD’s Secure Encrypted Virtualization (SEV) feature that extends the AMD-V architecture has been enabled in UEK Release 5. Hardware that supports SEV can use this feature to run multiple virtual machines under the control of a hypervisor in a more secure fashion. User-Mode Instruction Prevention (UMIP) for Intel enabled. Intel’s UMIP feature has been enabled in UEK Release 5. UMIP is a security feature present in newer Intel processors, that can prevent the execution of certain instructions if the Current Privilege Level (CPL) is greater than 0. Paravirtual TLB shootdown implemented. Patches have been applied to implement a KVM paravirtual translation lookaside buffer (TLB) shootdown algorithm.
Linux Containers	It’s easier than ever to get the most out of your systems with Linux Containers (LXC) and Docker. Deploy applications quickly and efficiently with Linux container technologies. You can easily build your own or download ours from Oracle Container Registry, Docker Hub, and Docker Store.
Updated Drivers and Hardware Support	The UEK Release 6 supports a wide range of hardware and devices. In close cooperation with our enterprise solution hardware partners, UEK updates deliver support for the latest hardware features and driver updates.
Security Improvements	In addition to ongoing CVE fixes, notable security improvements include: Secure boot improvements. Secure boot is designed to protect a system against malicious code being loaded and executed early in the boot process. Secured platforms load only software binaries, such as option ROM drivers, boot loaders, and operating system loaders, that are unmodified and trusted by the platform. While the operating system is loaded, measures have been added to prevent malicious code from being injected on subsequent boots.

The Unbreakable Enterprise Kernel Release 6 is the latest UEK release and is heavily tested and optimized operating system kernel for Oracle Linux 7 Update 9 and Oracle Linux 8 Update 1 and later on the x86-64 and 64-bit ARM (aarch64) architectures. It is based on the mainline Linux kernel version 5.4.

The Unbreakable Enterprise Kernel Release 5 is the Oracle’s fifth major release of its heavily tested and optimized operating system kernel for Oracle Linux 7 Update 5 and later on the x86-64 and 64-bit ARM (aarch64) architectures. It is based on the mainline Linux kernel version 4.14.35.

Partners Support Oracle Linux

Scores of leading technology partners—independent software vendors, hardware vendors, and system integrators—stand behind Oracle Linux, the best enterprise Linux. Oracle Linux is modern, fast, optimized for Oracle and works out-of-the-box with partners solutions supported on Red Hat Enterprise Linux.

Partner List

The table below provides a sample of the ever-growing list independent software vendors, hardware vendors, and system integrators that support Oracle Linux.

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