In this tutorial I will share multiple commands and methods you can use to check the Linux kernel version. We know that kernel is the core component in Linux and it is important that you know what version of kernel the system is running.
Method 1: Check Linux kernel version using uname
uname is the most handy tool which is used to print the system information.
On RHEL/CentOS/Fedora
In the provided distributions the output of uname would be similar to
~]# uname -r 4.18.0-193.14.2.el8_2.x86_64
The output can be broken into below format
<major_version>-<minor_version>-<release>.<architecture>
Here,
4.18.0is the major version193.14.2is the minor versionel8_2is the releasex86_64is the architecture
To list the installed kernel:
~]# rpm -q kernel kernel-4.18.0-80.el8.x86_64 kernel-4.18.0-147.5.1.el8_1.x86_64 kernel-4.18.0-193.14.2.el8_2.x86_64
On SLES/OpenSuSE
The output of uname would be different with SLES release which is again the kernel version for SLES platform.
# uname -r 3.0.101-108.81-default
You can use uname -a to get more details on the kernel version, system architecture etc
# uname -a Linux cc01-nds-ins 3.0.101-108.81-default #1 SMP Fri Nov 2 18:02:20 UTC 2018 (2208a0f) x86_64 x86_64 x86_64 GNU/Linux
To list the installed kernel:
~ # rpm -q kernel-default kernel-default-3.0.101-108.81.1
On Ubuntu/Debian
In the provided distribution, kernel is referred as linux-image. The kernel versions of Ubuntu/Debian are assigned by the respective developers and they don't follow the normal naming syntax or standards.
Output from my Ubuntu server:
# uname -r 5.0.0-23-generic
Here,
5is the major version0from the second field is the minor version0from the third field is the patch level23-genericis the developer patch level and in our context is what is assigned by the Ubuntu developers.
To list the available kernel package, you can use:
:~# dpkg --list | grep linux-image ii linux-image-5.0.0-23-generic 5.0.0-23.24~18.04.1 amd64 Signed kernel image generic ii linux-image-generic-hwe-18.04 5.0.0.23.80 amd64 Generic Linux kernel image
Method 2: Check Linux kernel version using hostnamectl
You may not find this command if you are using older releases. hostnamectl may be used to query and change the system hostname and related settings. But it also prints the kernel information.
The output of this command would be same across all Linux distributions. Below is an output from RHEL 8 server:
Method 3: Check Linux kernel version using grubby
grubby is only available in RHEL/CentOS/Fedora/SuSE distribution i.e. it is not yet available in Debian/Ubuntu (at the time of writing this article). grubby is a command line tool used to configure bootloader menu entries across multiple architectures.
To list the default kernel version:
~]# grubby --default-kernel /boot/vmlinuz-4.18.0-193.14.2.el8_2.x86_64
To get more information on this kernel, we can use "grubby --info /boot/vmlinuz-4.18.0-193.14.2.el8_2.x86_64". Following is an output from my server:
Method 4: Check Linux kernel version using boot log messages
4.1: Using dmesg
In most distributions we use dmesg to access the boot up log messages which also contains the kernel version along with many other details.
Output from RHEL/CentOS/Fedora
~]# dmesg | grep "Linux version"
[ 0.000000] Linux version 4.18.0-193.14.2.el8_2.x86_64 (mockbuild@kbuilder.bsys.centos.org) (gcc version 8.3.1 20191121 (Red Hat 8.3.1-5) (GCC)) #1 SMP Sun Jul 26 03:54:29 UTC 2020
Output from Ubuntu/Debian
~# dmesg | grep "Linux version"
[ 0.000000] Linux version 5.0.0-23-generic (buildd@lgw01-amd64-030) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #24~18.04.1-Ubuntu SMP Mon Jul 29 16:12:28 UTC 2019 (Ubuntu 5.0.0-23.24~18.04.1-generic 5.0.15)
Output from SLES
# dmesg | grep "Linux version"
[ 0.000000] Linux version 3.0.101-108.81-default (geeko@buildhost) (gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux) ) #1 SMP Fri Nov 2 18:02:20 UTC 2018 (2208a0f)
4.2: Using journalctl
In recent Linux distributions we have journalctl which gives us more flexibility in reading and accessing the log messages. To check the boot up log messsages we use -b switch with journalctl command
Output from RHEL/CentOS/Fedora
~]# journalctl -b | grep "Linux version" Sep 18 11:50:55 server.example.com kernel: Linux version 4.18.0-193.14.2.el8_2.x86_64 (mockbuild@kbuilder.bsys.centos.org) (gcc version 8.3.1 20191121 (Red Hat 8.3.1-5) (GCC)) #1 SMP Sun Jul 26 03:54:29 UTC 2020
Output from Ubuntu/Debian
~# journalctl -b | grep "Linux version" Sep 18 11:50:51 deepak-VirtualBox kernel: Linux version 5.0.0-23-generic (buildd@lgw01-amd64-030) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #24~18.04.1-Ubuntu SMP Mon Jul 29 16:12:28 UTC 2019 (Ubuntu 5.0.0-23.24~18.04.1-generic 5.0.15)
Currently I don't have access to SLES 12 or higher so I can't post the output but the same command would work with any SLES release higher than SLES 12.
Method 5: Check content of /proc/version
The output which you got earlier in Method 4 by grepping "Linux version" from the boot log files is actually collected from /proc/version. So if you do not wish to go through the log files, you can directly check the content of this file to get the Linux kernel version
Output from RHEL/CentOS/Fedora
~]# cat /proc/version
Linux version 4.18.0-193.14.2.el8_2.x86_64 (mockbuild@kbuilder.bsys.centos.org) (gcc version 8.3.1 20191121 (Red Hat 8.3.1-5) (GCC)) #1 SMP Sun Jul 26 03:54:29 UTC 2020
Output from SuSE/OpenSuSE
# cat /proc/version
Linux version 3.0.101-108.81-default (geeko@buildhost) (gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux) ) #1 SMP Fri Nov 2 18:02:20 UTC 2018 (2208a0f)
Output from Ubuntu/Debian
~# cat /proc/version
Linux version 5.0.0-23-generic (buildd@lgw01-amd64-030) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #24~18.04.1-Ubuntu SMP Mon Jul 29 16:12:28 UTC 2019
Conclusion
In this tutorial I shared multiple commands and methods to check Linux kernel version across multiple distributions such as Ubuntu, Red Hat, CentOS, Fedora, SuSE etc. Some of the commands may not work on all the distributions which I have already highlighted wherever applicable.
Lastly I hope the steps from the article to configure NIC teaming on Linux was helpful. So, let me know your suggestions and feedback using the comment section.
