At server side I have:

CentOS 7 updated
Kernel 4.13.12-1.el7.elrepo.x86_64

At clients side, exactly same environment.

We have a iptables, but it allow any comunication between clients and server (any port with any protocol).

Most of clients can connect and mount an exported NFS share directory normally, without any problem. They have exactly same environment with exactly same iptable rules.

Some of them can not mount NFS share and I have no logs about that.

Calling one of that problematic client as CLIENT-A, if I try to mount NFS manually, I have no error or warning or any kind of log:

[root@]#  mount -vvv -t nfs MYSERVER:/home/shared/ /home/shared/

Sometimes that command hang the terminal, sometimes not. If I cancel that command or do a new ssh and try to do ls in /home, terminal will hang:

[root@]# ls /home/sha

(when I pressed TAB it crashed with no error). Even if I try write manually and press enter, I will get same situation. It will only stop crash after reboot the server. "lsof" command will hang too.

And in both situations above there is no timeout error. They never finish. I already tried reboot and try again, with no success. And I repeat: They have exactly same environment. You can think as a clone with different hardware and IP, but same software. Yes, it not guarantee equally results, but in general the idea of softwares are show same result.

I can create a tcp connection with NFS server manually:

[root@localhost]# telnet MYSERVER 2049
Connected to MYSERVER.
Escape character is '^]'.

I have no logs in both sides about what is happening. I think they are trying to create a connection with nfs 4.1 version (last version of that module). I have tried version 3 manually with no success.

I executed "rpcinfo -p localhost" at server side and I found a curious question: Some clients are using version 4, some of them 3, 2 or 1 (2 or 1????!!!).

[root@ ~]# rpcinfo -p  localhost
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
100024    1   udp  59356  status
100024    1   tcp  50117  status
100005    1   udp  20048  mountd
100005    1   tcp  20048  mountd
100005    2   udp  20048  mountd
100005    2   tcp  20048  mountd
100005    3   udp  20048  mountd
100005    3   tcp  20048  mountd
100003    3   tcp   2049  nfs
100003    4   tcp   2049  nfs
100227    3   tcp   2049  nfs_acl
100003    3   udp   2049  nfs
100227    3   udp   2049  nfs_acl
100021    1   udp  58205  nlockmgr
100021    3   udp  58205  nlockmgr
100021    4   udp  58205  nlockmgr
100021    1   tcp  38641  nlockmgr
100021    3   tcp  38641  nlockmgr
100021    4   tcp  38641  nlockmgr

So I found one client that are using NFSV3 and I did:

[root@ ~]# mount -vvv -t nfs -o vers=4     MYSERVER:/home/shared/ /home/shared/
mount.nfs: timeout set for Sun Nov 12 14:03:02 2017
mount.nfs: trying text-based options 'vers=4.1,addr=MYSERVER,clientaddr=MYCLIENTIP'

It hangs. But if I try vers=3, it works.

[root@ ~]# mount -vvv -t nfs -o vers=3 MYSERVER:/home/shared/ /home/shared/
mount.nfs: timeout set for Sun Nov 12 14:03:12 2017
mount.nfs: trying text-based options 'vers=3,addr=MYSERVERIP'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying MYSERVERIP prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying MYSERVERIP prog 100005 vers 3 prot UDP port 20048

At server side, the directory are exported line-by-line to different IPs with same parameters:


Returning at CLIENT-A question, I tried to log every new connection from tcp and udp ports from CLIENT-A in server side. I can see CLIENT-A trying to open ports. And it tries a lot. So I think the problem is not with clients. Maybe.

So my questions are:

  1. How to troubleshooting from now? I only have logs at server side from RPC when remote mount get success.
  2. Why rpcinfo -p show all versions about nfs4?
  3. Why (maybe relationated with (1)) server equally configured broke in nfs v4.1 and not with 3? OK, I know about stability questions, but with no logs about errors is the major question.

Thank you for your time :)

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