Skip to main content

Change default grub boot kernel – CentOS/RHEL/OEL 7

How to modify the GRUB2 default entry to boot a different Kernel version?


1. Check the current running Kernel Version
# uname -a
Linux geeklab 3.8.13-94.el7uek.x86_64 #2 SMP Wed Feb 11 14:18:22 PST 2015 x86_64 x86_64 x86_64 GNU/Linux
2. List the Kernel Entries as per GRUB2 file:

# awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg
Oracle Linux Server, with Unbreakable Enterprise Kernel 3.8.13-94.el7uek.x86_64
Oracle Linux Server, with Unbreakable Enterprise Kernel 3.8.13-94.el7uek.x86_64 with debugging
Oracle Linux Server 7.1, with Linux 3.10.0-229.el7.x86_64
Oracle Linux Server 7.1, with Unbreakable Enterprise Kernel 3.8.13-55.1.6.el7uek.x86_64
Oracle Linux Server 7.1, with Linux 0-rescue-441e86c9ff854310a306bd33e56aae2b

NOTE: The first entry is denoted as Zero. So currently the Server is booted to 0th entry as per the above `uname -a` command output.


3. Let us modify the Kernel Version to 3.8.13-55.1.6.el7uek.x86_64 which is at line number 4 but denoted as entry

# grub2-set-default 3

4: Changes to /etc/default/grub require rebuilding the grub.cfg file as follows:

# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.10.0-229.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-229.el7.x86_64.img
Found linux image: /boot/vmlinuz-3.8.13-94.el7uek.x86_64
Found initrd image: /boot/initramfs-3.8.13-94.el7uek.x86_64.img
Found linux image: /boot/vmlinuz-3.8.13-55.1.6.el7uek.x86_64
Found initrd image: /boot/initramfs-3.8.13-55.1.6.el7uek.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-441e86c9ff854310a306bd33e56aae2b
Found initrd image: /boot/initramfs-0-rescue-441e86c9ff854310a306bd33e56aae2b.img
done

Reboot the Server and it will boot with Kernel Version 3.8.13-55.1.6.el7uek.x86_64.
# shutdown -r now

Comments

  1. iyn80gm5izJanuary 3, 2023 at 1:36 AM

    Our editorial group ensures we solely release quality articles would possibly be} readworthy. Coming to terms with 온라인 카지노 the fact that|the truth that} you might be an addict is not easy, and it usually requires exterior help. Online remedy and help groups are available, they usually can provide you with the necessary assist you to are looking for. When gambling habit strikes, it’s hardly fairly or one thing easy to cope with. Excessive gambling practices can lead you to burn through your financial savings at a fast and foolhardy pace that leaves you penniless and precipitates anxiety, despair, recklessness, and more. Online gamblers can simply go from completely pleased ordinary people to someone who experiences emotional and financial turmoilthat makes day by day life a challenge.

    ReplyDelete

Post a Comment

Popular posts from this blog

Unix / Linux - File Management

We are going to discuss in detail about file management in Unix. All data in Unix is organized into files. All files are organized into directories. These directories are organized into a tree-like structure called the filesystem. When you work with Unix, one way or another, you spend most of your time working with files. This tutorial will help you understand how to create and remove files, copy and rename them, create links to them, etc. In Unix, there are three basic types of files − Ordinary Files   − An ordinary file is a file on the system that contains data, text, or program instructions. In this tutorial, you look at working with ordinary files. Directories   − Directories store both special and ordinary files. For users familiar with Windows or Mac OS, Unix directories are equivalent to folders. Special Files   − Some special files provide access to hardware such as hard drives, CD-ROM drives, modems, and Ethernet adapters. Other special files are similar to aliases or shortcu
1 comment
Read more

Big 'O' Notation | Big O Cheat Sheet

Big O notation is used in Computer Science to describe the performance or complexity of an algorithm. Big O specifically describes the worst-case scenario and can be used to describe the execution time required or the space used (e.g. in memory or on disk) by an algorithm. -Big Os O(1) Constant- no loops O(log N) Logarithmic- usually searching algorithms have log n if they are sorted (Binary Search) O(n) Linear- for loops, while loops through n items O(n log(n)) Log Liniear- usually sorting operations  O(n^2) Quadratic- every element in a collection needs to be compared to ever other element. Two nested loops O(2^n) Exponential- recursive algorithms that solves a problem of size N O(n!) Factorial- you are adding a loop for every element Iterating through half a collection is still O(n)  Two separate collections: O(a * b)  -What can cause time in a function?- Operations (+, -, *, /) Comparisons (<, >, ==) Looping (for, while) Outside Function call (function())   -Rule Book Ru
3 comments
Read more