It seems the system can't boot correctly after running a yum update and grub prompt appears. I'm not sure but maybe memory was exhausted in the process. The thing is I don't know what is the real issue and how to solve it. When I try with these commands:
grub>boot
Error 8: Kernel must be loaded before booting
grub>root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
I've checked some topics in the forums with no success.
Any help will be appreciated.
Many thanks
P.S. I don't have a CD or similar for booting purposes. It's a server from vultr and this was the response from them: "the instance seems to be sitting at a grub prompt, you will need to access the host from the console and troubleshoot the issue from there".