mount: mount to NFS server '192.168.29.100' failed: System Error: Connection refused.
解决方法：
yum install portmap
然后
/etc/init.d/portmap start
/etc/init.d/nfs start
然后
mount -a
一切ok！
另外，转一篇文章
Linux下配置NFS(rpc服务启动必须NFS服务先起来)
环境：client: 主机rac2,ip 192.168.0.6
server: 主机rac1,ip 192.168.0.5
1) 在客户端启动portmap和nfs服务，单起nfs进程是无法启动的。
[root@rac2 init.d]# ./nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: Cannot register service: RPC: Unable to receive; errno = Connection refused
rpc.rquotad: unable to register (RQUOTAPROG, RQUOTAVERS, udp).
[FAILED]
Starting NFS daemon:
[FAILED]
Starting NFS mountd: Cannot register service: RPC: Unable to receive; errno = Connection refused
mountd: unable to register (mountd, 1, udp).
[FAILED]
Starting RPC idmapd: [ OK ]
[root@rac2 init.d]# ps -ef|grep nfs
证明nfs没有启动。
[root@rac2 init.d]# /etc/init.d/portmap start
Starting portmap: [ OK ]
[root@rac2 init.d]# ps -ef|grep portmap
rpc 3198 1 0 02:39 ? 00:00:00 portmap
root 3202 2998 0 02:39 pts/0 00:00:00 grep portmap
[root@rac2 init.d]# /etc/init.d/nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: [ OK ]
Starting NFS daemon: [ OK ]
Starting NFS mountd: [ OK ]
启动正常，检查一下nfs进程是否在。
[root@rac2 init.d]# ps -ef|grep nfs
root 3222 1 0 02:39 ? 00:00:00 [nfsd]
root 3223 1 0 02:39 ? 00:00:00 [nfsd]
root 3224 1 0 02:39 ? 00:00:00 [nfsd]
root 3225 1 0 02:39 ? 00:00:00 [nfsd]
root 3226 1 0 02:39 ? 00:00:00 [nfsd]
root 3227 1 0 02:39 ? 00:00:00 [nfsd]
root 3228 1 0 02:39 ? 00:00:00 [nfsd]
root 3231 1 0 02:39 ? 00:00:00 [nfsd]
root 3260 2998 0 02:45 pts/0 00:00:00 grep nfs
rac1上有一个/disk0分区，看从rac2能否直接连接上rac1
[root@rac1 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda5 2.9G 2.3G 503M 83% /
/dev/sda1 99M 12M 83M 12% /boot
none 125M 0 125M 0% /dev/shm
/dev/sda2 7.7G 2.3G 5.1G 32% /home
/dev/sda3 3.9G 2.3G 1.4G 62% /usr
/dev/sda7 2.8G 1.1G 1.6G 40% /var
/dev/sdb5 1004M 1.3M 952M 1% /disk0
[root@rac2 init.d]# mount 192.168.0.5:/disk0 /wyl (/wyl目录必须已存在)
mount: mount to NFS server '192.168.0.5' failed: System Error: Connection refused.
报错信息指的是server端(Rac1)的nfs进程没起来！
在服务端启动nfs进程(实际上是要启动portmap和nfs进程)
[root@rac1 ~]# /etc/init.d/portmap start
Starting portmap: [ OK ]
[root@rac1 ~]# /etc/init.d/nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: [ OK ]
Starting NFS daemon: [ OK ]
Starting NFS mountd: [ OK ]
Starting RPC idmapd: [ OK ]