[Linux][CentOS] Boot Kernel quantity 修改
OS Version: CentOS 7.5.1804**
Grub2 Version: grub2-2.02-0.65
This is a command record for CentOS kernel, all the command come from internet reference.
List all available kernel images added to GRUB2
grep '^menuentry' /boot/grub2/grub.cfg
or use rpm to list all kernel
rpm -qa kernel
Change the number of kernel in two way
Temporary:
yum install yum-utils
package-cleanup --problems (To list dependency problems in the local RPM database)
package-cleanup --leaves (To display the RPMs that are not relied upon by any other RPM)
package-cleanup --orphans (To list installed packages which are not available from currently configured repositories)
package-cleanup --dupes (To scan for duplicates in the local RPM database)
Note: If you get any duplicate RPMs in the local database, you can use the --cleandupes option to remove them.
The --oldkernels and --count options allows you to define the number of old kernels to keep.
package-cleanup --oldkernels --count=2
Permanent:
You can find out the default number of kernel value is 5, you can change it to the number you want.
vim /etc/yum.conf
installonly_limit=3
After you change the number, you can delete old kernet and reboot your system.
package-cleanup --oldkernels --count=3
reboot
Change the Default Kernel Version Permanently on CentOS 7
You can find out the numeric value when you cat /boot/grub2/grub.cfg, the top one is 3.10.0-862.9.1 this numeric value is 0. So, if you want 3.10.0-693.2.2 become the default kernel you can do this:
vim /etc/default/grub
GRUB_DEFAULT=2
After you insert or change the value, you need to regenerate grub config
grub2-mkconfig -o /boot/grub2/grub.cfg
Then reboot your system and you will see the kernel you selected.
Change the Default Kernel Version Permanently on CentOS 6 or earlier
grep '^[[:space:]]*kernel' /boot/grub/grub.conf
vim /boot/grub/grub.conf
default=1
Change the Default Boot Kernel Temporarily on CentOS
CentOS 7:
grub2-reboot 2
reboot
CentOS 6:
echo "savedefault --default=2 --once" | grub --batch
reboot
Reference
How to change default boot kernel permanently or temporarily on CentOS