Linux：clnt_create：RPC：プログラムが登録されていません。

NFS マウントが最近自動的にマウント解除されました。確認してみると、NFSサービスのステータスが実行中としてマークされました。

[root@hsluasrepo]# service nfs status
rpc.svcgssd is stopped
rpc.mountd (pid 4083) is running...
nfsd (pid 4148 4147 4146 4145 4144 4143 4142 4141) is running...
rpc.rquotad (pid 4079) is running...

[root@hsluasrepo]# service rpcbind status
rpcbind (pid  4203) is running...

[root@hsluasrepo common]# rpcinfo -p 10.80.3.154
   program vers proto   port  service
    100000    4   tcp    111  portmapper
    100000    3   tcp    111  portmapper
    100000    2   tcp    111  portmapper
    100000    4   udp    111  portmapper
    100000    3   udp    111  portmapper
    100000    2   udp    111  portmapper

ただし、showmount出力にエラーが表示されます。

[root@hsluasrepo ]# showmount -e 10.80.3.154
clnt_create: RPC: Program not registered

NFSサービスを再起動すると、showmount出力にエクスポートされたNFSサーバーのリストが表示されます。

この問題の根本原因と、今後これを防ぐ方法を教えてくれる人はいますか？

/var/log/messages:

Jul 7 03:22:01 hsluasrepo rsyslogd: [origin software="rsyslogd" swVersion="5.8.10" x-pid="1188" x-info="rsyslog.com"] rsyslogd was HUPed
Jul 7 03:22:02 hsluasrepo rhsmd: In order for Subscription Manager to provide your system with updates, your system must be registered with RHN. Please enter your Red Hat login to ensure your system is up-to-date.
Jul 8 03:22:01 hsluasrepo rhsmd: In order for Subscription Manager to provide your system with updates, your system must be registered with RHN. Please enter your Red Hat login to ensure your system is up-to-date.
Jul 8 16:36:55 hsluasrepo kernel: nfsd: last server has exited, flushing export cache
Jul 8 16:36:55 hsluasrepo rpc.mountd[4083]: Caught signal 15, un-registering and exiting.
Jul 8 16:36:55 hsluasrepo rpc.mountd[24463]: Version 1.2.3 starting
Jul 8 16:36:55 hsluasrepo kernel: NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
Jul 8 16:36:55 hsluasrepo kernel: NFSD: starting 90-second grace period
Jul 8 16:37:32 hsluasrepo rpc.mountd[24463]: authenticated mount request from 10.60.5.208:1004 for /common/PROD (/common/PROD)
Jul 8 16:38:09 hsluasrepo rpc.mountd[24463]: authenticated mount request from 10.60.5.181:869 for /common/PROD (/common/PROD) 
Jul 8 16:38:43 hsluasrepo rpc.mountd[24463]: authenticated mount request from 10.60.5.180:825 for /common/PROD (/common/PROD)
Jul 8 16:39:12 hsluasrepo rpc.mountd[24463]: authenticated mount request from 10.60.5.176:688 for /common/PROD (/common/PROD)