Linux kernel version names

Linux kernel version numbers?

I’m somewhat confused on the Linux kernel version numbers. I noticed that many Linux distributions do no use the latest Kernels, in fact I have seen a few using version 2.4. Is there a reason for this? Is there any differences between 2.4, 2.6, 3.2 apart from age? What are the security implications of using an older kernel?

6 Answers 6

Different kernels have different features and improvements the developers of a distribution take a look at features they are going to support then decide which kernel to use based on the most stable support of that kernel.

It is the decision of the distribution developer which one to use, and they would go with the one they felt comfortable with.

This is a feature of software development its like asking what Java 1.1 and Java 1.7 is and whats the difference is apart from age. the answer is many things.

Most kernels and software will also have a security patch schedule and it is up to the user to keep their systems patched and up to date if you do not then you invite security issues as they are never fixed.

between major releases (e.g. 2.4 and 2.6), new features are introduced and old features are deprecated, eventually making the kernel binary incompatible.

this is important if you depend on some kernel-module that is not part of the mainline kernel (e.g. it is proprietary and the original authors don’t provide updated modules; or it is open source (but never made it into the kernel) and nobody is willing to spend time to migrate the code)

also a new major release might change the system behaviour significantly. i remember that when switching from 2.4 to 2.6, many people that needed low latency audio (that’s my background, so forgive me) would stay with the old kernel, since the new scheduling algorithms performed worse in some situations.

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Active kernel releases

There are several main categories into which kernel releases may fall:

Prepatch Prepatch or «RC» kernels are mainline kernel pre-releases that are mostly aimed at other kernel developers and Linux enthusiasts. They must be compiled from source and usually contain new features that must be tested before they can be put into a stable release. Prepatch kernels are maintained and released by Linus Torvalds. Mainline Mainline tree is maintained by Linus Torvalds. It’s the tree where all new features are introduced and where all the exciting new development happens. New mainline kernels are released every 9-10 weeks. Stable After each mainline kernel is released, it is considered «stable.» Any bug fixes for a stable kernel are backported from the mainline tree and applied by a designated stable kernel maintainer. There are usually only a few bugfix kernel releases until next mainline kernel becomes available — unless it is designated a «longterm maintenance kernel.» Stable kernel updates are released on as-needed basis, usually once a week. Longterm There are usually several «longterm maintenance» kernel releases provided for the purposes of backporting bugfixes for older kernel trees. Only important bugfixes are applied to such kernels and they don’t usually see very frequent releases, especially for older trees.

Longterm release kernels

Version	Maintainer	Released	Projected EOL
6.1	Greg Kroah-Hartman & Sasha Levin	2022-12-11	Dec, 2026
5.15	Greg Kroah-Hartman & Sasha Levin	2021-10-31	Oct, 2026
5.10	Greg Kroah-Hartman & Sasha Levin	2020-12-13	Dec, 2026
5.4	Greg Kroah-Hartman & Sasha Levin	2019-11-24	Dec, 2025
4.19	Greg Kroah-Hartman & Sasha Levin	2018-10-22	Dec, 2024
4.14	Greg Kroah-Hartman & Sasha Levin	2017-11-12	Jan, 2024

Distribution kernels

Many Linux distributions provide their own «longterm maintenance» kernels that may or may not be based on those maintained by kernel developers. These kernel releases are not hosted at kernel.org and kernel developers can provide no support for them.

It is easy to tell if you are running a distribution kernel. Unless you downloaded, compiled and installed your own version of kernel from kernel.org, you are running a distribution kernel. To find out the version of your kernel, run uname -r :

# uname -r 5.6.19-300.fc32.x86_64

If you see anything at all after the dash, you are running a distribution kernel. Please use the support channels offered by your distribution vendor to obtain kernel support.

Releases FAQ

Here are some questions we routinely receive about kernel release versions. See also the main «FAQ» section for some other topics.

When is the next mainline kernel version going to be released?

Linux kernel follows a simple release cadence:

• after each mainline release, there is a 2-week «merge window» period during which new major features are introduced into the kernel
• after the merge window closes, there is a 7-week bugfix and stabilization period with weekly «release candidate» snapshots
• rc7 is usually the last release candidate, though occasionally there may be additional rc8+ releases if that is deemed necessary

So, to find the approximate date of the next mainline kernel release, take the date of the previous mainline release and add 9-10 weeks.

What is the next longterm release going to be?

Longterm kernels are picked based on various factors — major new features, popular commercial distribution needs, device manufacturer demand, maintainer workload and availability, etc. You can roughly estimate when the new longterm version will become available based on how much time has elapsed since the last longterm version was chosen.

Why are some longterm versions supported longer than others?

The «projected EOL» dates are not set in stone. Each new longterm kernel usually starts with only a 2-year projected EOL that can be extended further if there is enough interest from the industry at large to help support it for a longer period of time.

Does the major version number (4.x vs 5.x) mean anything?

No. The major version number is incremented when the number after the dot starts looking «too big.» There is literally no other reason.

Does the odd-even number still mean anything?

A long time ago Linux used a system where odd numbers after the first dot indicated pre-release, development kernels (e.g. 2.1, 2.3, 2.5). This scheme was abandoned after the release of kernel 2.6 and these days pre-release kernels are indicated with «-rc».

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How to Check Linux Kernel Version

Kernel is one of the most significant components of the Linux operating system. The kernel is used to manage resources, processes, and provides methods for hardware and software communication. It is important to know the exact Linux Kernel version to install correct software packages, bug fixes, and patches.

In this tutorial, we will discuss different methods to check a Linux kernel version, and explain what each number in the version string means.

What is Kernel Version

The kernel is the control center of your Linux operating system, which ensures operating system security and stability. All Linux operating systems and their distributions may have a different Kernel version.

An updated kernel is required for a secure and stable Linux system. You must also know the Linux kernel version when debugging hardware or software issues, installing new packages, installing bug fixes, or applying patches.

Open the terminal and run the following command:

Kernel Version Format

Each number in the Kernel version string is separated either by a dot or a hyphen.

Let’s understand what these numbers mean:

• 5 — First number is the main version.
• 13 — Second number is the major revision.
• 0 — Third number is the minor revision.
• 27 — Fourth number is the patch and bug fixes level.
• generic — This string could be different for each Linux distribution. We are using Ubuntu distribution desktop version, and thus it is showing generic. This could also be the machine architecture, such as x86_64.

The Linux Kernel versions must always match exactly with the supported version before you perform any updates, debugs, installs, or diagnoses on your Linux system.

Commands to Check Kernel Version Linux

The Linux operating system comes equipped with various commands to display Kernel versions. The output of all these commands is different. Some of these commands provide only the kernel version, whereas others provide more detailed system information.

You can check the Linux kernel version using the following commands.

Command	Description
uname -r	Displays only the Kernel version.
cat /proc/version	Displays Kernel version along with Kernel build and compile date.
hostnamectl | grep Kernel	Displays Kernel version along with Linux version, kernel name, system hostname, computer name, and CPU architecture.
dmesg | grep Linux	Displays Kernel version along with other system configurations.

Examples to Check Kernel Version in Linux

Your Linux operating system may display the kernel release number in a bit different format. For example, the Red Hat Linux enterprise version shows kernel type and architecture such as el8_2_x86-64 along with the version number.

In the following examples, we will show the different ways to check the kernel version.

uname -r

The uname command with -r option is the commonly used method to find Linux kernel versions.

Use the following command to check the release number of the Linux Kernel:

You can combine this output with other uname command options, such as -v to display kernel compile date.

cat /proc/version

When your Linux computer starts, a virtual file system proc is created. This file system disappears after you shut down the computer. Linux Kernel information is stored in the /proc/version file, which is used by Linux at runtime. Use the cat command line utility to print version information from this file:

From the output, we can see the version of Linux Kernel along with Linux version, version of gcc used to compile, time of kernel compilation, and username of the person who compiled.

hostnamectl | grep Kernel

The hostnamectl command is primarily used to display and change the hostname of your Linux computer. However, you can also use this command to display the Kernel release number:

In this example, we can see the hostnamectl command can be used with the grep command, or without the grep command. When used without the grep command, it also shows static hostname, VM machine ID, boot ID, OS distribution, and other system information.

dmesg | grep Linux

The dmesg command line utility is primarily used to print Kernel messages and read device driver messages.

Use the following command to filter kernel version from dmesg output:

Conclusion

In this tutorial, we learned how to check the Linux Kernel version using different commands.

These commands to check Kernel version works on all Linux distributions, including Ubuntu desktop, Ubuntu server, Red Hat, Debian, and Fedora.

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