kurtis318/How_to_boot_specific_kernel_in_RHEL.md

## How_to_boot_specific_kernel_in_RHEL.md

      
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              How_to_boot_specific_kernel_in_RHEL.md
            
          
    Issue:

There are times when a newly installed kernel has boot or runtime problems.  I need a way to boot a specific kernel automatically.
Solution:

REF: https://access.redhat.com/solutions/1605183
$ cat /etc/sysconfig/kernel
# UPDATEDEFAULT specifies if new-kernel-pkg should make
# new kernels the default
UPDATEDEFAULT=yes

# DEFAULTKERNEL specifies the default kernel package type
DEFAULTKERNEL=kernel

~]# awk -F\' '$1=="menuentry " {print $2}' /etc/grub2.cfg

Eg: 
~]#  awk -F\' '$1=="menuentry " {print $2}' /etc/grub2-efi.cfg 
Red Hat Enterprise Linux Server (3.10.0-693.el7.x86_64) 7.3 (Maipo)           <<==== Entry 0
Red Hat Enterprise Linux Server (3.10.0-514.el7.x86_64) 7.3 (Maipo)           <<==== Entry  1
Red Hat Enterprise Linux Server (0-rescue-d3c598b9d2204138bd2e1001316a5cc6) 7.3 (Maipo)

~]# grub2-set-default 1

~]# cat /boot/grub2/grubenv |grep saved

Eg:
~]# cat /boot/grub2/grubenv |grep saved
saved_entry=1


Rebuild the /boot/grub2/grub.cfg file by running the grub2-mkconfig -o command as follows:

On BIOS-based machines: ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
On UEFI-based machines: ~]# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg