Comparing the Default Kernel to the Running Kernel

The running kernel and the kernel configured as the default kernel that GRUB 2 selects to boot into after a timeout period for the boot menu can differ.

If the default kernel version and the running kernel version aren't identical, the underlying reasons might be one of the following:

A newer kernel is installed, but the system hasn't been rebooted.
During a system reboot, a different kernel was manually selected to be the operative kernel.
The default kernel was manually updated but the system hasn't been rebooted after the update.

To compare the default configured kernel to the running kernel, do the following:

Check the default kernel configured in GRUB 2.
To check which kernel is already configured as the current default kernel to use at boot, run:
```
sudo grubby --default-kernel
```
Check the running kernel version.
To check which kernel is running on a system, run:
```
uname -r
```