[Freeipa-users] kerbores nfs client problem

I set up a kerberos-aware nfs server and some clients. I mount with "-o sec=krb5" successfully first time. For some reason, I change the krb5.keytab by copying a backup keytab and rerunnig ipa-getkeytab command, and then reboot the nfs server. Now the client mounting succesfully before is unable to mount any more unless reboot, but other new clients are able to mount. How to fix those clients without rebooting.