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15.19. Configuring Clock Sources

To list the available clock sources on your system, issue the following commands:
~]$ cd /sys/devices/system/clocksource/clocksource0/
clocksource0]$ cat available_clocksource
kvm-clock tsc hpet acpi_pm 
clocksource0]$ cat current_clocksource
kvm-clock
In the above example, the kernel is using kvm-clock. This was selected at boot time as this is a virtual machine.
To override the default clock source, append the clocksource directive to the GRUB_CMDLINE_LINUX line in the /etc/default/grub file and rebuild the grub.cfg file. For example:
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root crashkernel=auto  rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet clocksource=tsc"
The available clock source is architecture dependent.
Rebuild the grub.cfg file as follows:
  • On BIOS-based machines, issue the following command as root:
    ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
  • On UEFI-based machines, issue the following command as root:
    ~]# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg