To install CentOS as a guest operating system using KVM and virt-manager, you can use the following steps:
virt-manager package on the host machine by running the following command:sudo apt-get install virt-manager
Download the ISO image of CentOS and copy it to the host machine.
Launch virt-manager from the command line or by searching for it in the application launcher.
Click the Create a new virtual machine button in the main window.
Select the Local install media (ISO image or CDROM) option and click Forward.
Select the ISO image of CentOS as the install media and click Forward.
Specify the desired configuration for the virtual machine, such as the amount of memory and number of CPUs.
Click Forward to proceed to the storage configuration.
Specify the size and location of the virtual machine's disk and click Forward.
Review the summary of the virtual machine's configuration and click Finish to create the virtual machine.
The virtual machine will be created and the installation process will begin. Follow the prompts to complete the installation of CentOS.