I've had this problem for a long time and I've never been able to solve it. I have a simple NFS setup between 2 FC5 boxes. I've never been able to get (what I think is) locking to work. NFS works great for 99% of uses/apps, but things that appear to do locking fail in strange ways. 1. OpenOffice's oocalc will take a long time to open a file across NFS and when it finally does, it's read-only. 2. Flock calls in perl will hang indefinitely over NFS. Here's my /etc/exports on the server: /data 192.168.100.1(rw,insecure,async,no_subtree_check,no_root_squash) Here's my fstab on the client: 192.168.100.2:/data /data nfs rw,hard,intr,timeo=10,nosuid,bg,udp,rsize=8192,wsize=8192 0 0 server: #cat /etc/sysconfig/nfs STATD_PORT=32765 STATD_OUTGOING_PORT=32766 MOUNTD_PORT=32767 RQUOTAD_PORT=32764 server: #ps -ef | grep -P '\[(lock|nfs)|statd|portmap' | grep -v grep rpc 2169 1 0 2006 ? 00:00:00 portmap root 2970 7 0 2006 ? 00:00:00 [nfsd4] root 2971 1 0 2006 ? 05:40:06 [nfsd] root 2972 1 0 2006 ? 05:34:22 [nfsd] root 2973 1 0 2006 ? 05:26:16 [nfsd] root 2974 1 0 2006 ? 00:00:00 [lockd] root 2976 1 0 2006 ? 05:33:17 [nfsd] root 2977 1 0 2006 ? 05:27:06 [nfsd] root 2978 1 0 2006 ? 05:29:35 [nfsd] root 2979 1 0 2006 ? 05:25:46 [nfsd] root 2980 1 0 2006 ? 05:33:20 [nfsd] rpcuser 23364 1 0 2006 ? 00:00:00 rpc.statd -p 32765 -o 32766 client: #ps -ef | grep -P '\[(lock|nfs)|statd|portmap' | grep -v grep rpc 3077 1 0 Jun15 ? 00:00:03 portmap root 3095 1 0 Jun15 ? 00:00:00 [lockd] server iptables rules (abbreviated version!): [ "$HAVE_NFS" = 1 ] && iptables -A fragments -s $nfsallow -j RETURN iptables -A fragments -j DROP iptables -A aad_first -f -j fragments if [ "$HAVE_NFS" = 1 ]; then iptables -N nfs iptables -A nfs -p tcp --dport sunrpc -j ACCEPT iptables -A nfs -p udp --dport sunrpc -j ACCEPT iptables -A nfs -p tcp --dport nfs -j ACCEPT iptables -A nfs -p udp --dport nfs -j ACCEPT iptables -A nfs -p tcp --dport 32765:32768 -j ACCEPT iptables -A nfs -p udp --dport 32765:32768 -j ACCEPT iptables -A iint -s "$nfsallow" -j nfs iptables -A aaa_persist -s "$nfsallow" -p tcp --dport sunrpc -j RETURN iptables -A aaa_persist -s "$nfsallow" -p udp --dport sunrpc -j RETURN iptables -A aaa_persist -s "$nfsallow" -p tcp --dport nfs -j RETURN iptables -A aaa_persist -s "$nfsallow" -p udp --dport nfs -j RETURN iptables -A aaa_persist -s "$nfsallow" -p tcp --dport 32765:32768 -j RETURN iptables -A aaa_persist -s "$nfsallow" -p udp --dport 32765:32768 -j RETURN fi rules are the same on both client & server. What am I missing to make locking work and have a happy NFS setup?