[kumara@localhost ~]$ su
Password:
[root@localhost kumara]# yum update

You have enabled checking of packages via GPG keys. This is a good thing.
However, you do not have any GPG public keys installed. You need to download
the keys for packages you wish to install and install them.
You can do that by running the command:
    rpm --import public.gpg.key
For more information contact your distribution or package provider.
[root@localhost kumara]# rpm --import public.gpg.key
error: public.gpg.key: import read failed.
[root@localhost kumara]# rpm --import public.gpg.key
error: public.gpg.key: import read failed.
[root@localhost kumara]#