1. View the current system kernel
uname -r
3.18.6-2.el7.centos.x86_64
View the list of available kernels
awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg
The result is as follows:
0 : CentOS Linux (3.18.6-2.el7.centos.x86_64) 7 (Core)1 : CentOS Linux (3.10.0-514.el7.x86_64) 7 (Core)2 : CentOS Linux (0-rescue-05653d304ed443db9b60529d6cf7d242) 7 (Core)
2. View the current default kernel startup items
grub2-editenv list
The result is as follows:
saved_entry=0
That is, the kernel loaded by default when the system is currently started is CentOS Linux (3.18.6-2.el7.centos.x86_64) 7 (Core)
3. Change the default startup kernel item
grub2-set-default 1
Check the default kernel boot entry again and find that the saved_entry field has changed to 1
4. Restart the system
reboot
View the current system kernel
uname -r
3.10.0-514.el7.x86_64
You can see that the kernel of the current system has been changed