From the NFS Server, do put in the command below. The NFS Server is 192.168.0.1 and the NFS Server port is 2049
# netstat -an | grep 192.168.0.1:2049
tcp 0 0 192.168.0.1:2049 192.168.0.10:965 ESTABLISHED
(192.168.0.10 is the client)
NFS
Networked File System
How to configure NFS on CentOS 7
Step 1: Do a Yum Install
# yum install nfs-utils rpcbind
Step 2: Enable the Service at Boot Time
# systemctl enable nfs-server # systemctl enable rpcbind # systemctl enable nfs-lock (it does not need to be enabled since rpc-statd.service is static.) # systemctl enable nfs-idmap (it does not need to be enabled since nfs-idmapd.service is static.)
Step 3: Start the Services
# systemctl start rpcbind # systemctl start nfs-server # systemctl start nfs-lock # systemctl start nfs-idmap
Step 4: Confirm the status of NFS
# systemctl status nfs
Step 5: Create a mount point
# mkdir /shared-data
Step 6: Exports the Share
# vim /etc/exports /shared-data 192.168.0.0/16(rw,no_root_squash)
Step 7: Export the Share
# exportfs -rv
Step 8: Restart the NFS Services
# systemctl restart nfs-server
Step 9: Configure the Firewall
# firewall-cmd --add-service=nfs --zone=internal --permanent # firewall-cmd --add-service=mountd --zone=internal --permanent # firewall-cmd --add-service=rpc-bind --zone=internal --permanent
References:
How to unmount NFS mount that fails to unmount with ‘device is busy’
If you are attempting to unmount a NFS command like
# mount -t nfs -o remount /mnt/nfs # umount /mnt/nfs # umount -f /mnt/nfs # umount -l /mnt/nfs # umount -lf /mnt/nfs
Identify which processes tied to the mount need to be killed by using lsof and fuser:
# lsof | grep /mnt/nfs
lsof command above identifies the PID of the processes associated with the /mnt/nfs share. Kill any processes locking the stale mount.
Try to force umount again after the processes as been killed
# umount -lf
References:
Increasing NFS Performance by using nconnect
nconnect is included in linux kernel versions >= 5.3. What is nconnect? nconnect enables multiple TCP connections for a single NFS mount. It is easy to implement
At /etc/fstab
mount -t nfs -o rw,nconnect=16 192.168.1.0:/applications /user/local
References:
How to increase the number of threads created by the NFS daemon for CENTOS 7
Taken from How to increase the number of threads created by the NFS daemon in RHEL 4, 5, 6 and 7?
In case of a NFS server with a high load, it may be advisable to increase the number of the threads created during the nfsd server start up.
Edit the following line in /etc/nfs.conf
% vim /etc/nfs.conf
#[nfsd] # debug=0 threads=64 # host= # port=0 # grace-time=90 # lease-time=90 # udp=y # tcp=y
Testing whether it works….
% cat /proc/net/rpc/nfsd
According to the RH, “The first number is the total number of NFS server threads started. The second number indicates whether at any time all of the threads were running at once. The remaining numbers are a thread count time histogram.”
th 64 0 2.610 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
mount.nfs: requested NFS version or transport protocol is not supported
If you have encountered issues like
mount.nfs: requested NFS version or transport protocol is not supported
OR
mount.nfs4: Protocol not supported
To resolve this
Mount with NFS version 3 (with 4 verbose flags)
% mount -vvvv -t nfs -o vers=3 nfs-server:/share /mnt/nfs
References:
showmount fails with clnt_create: RPC: Program not registered from a NFS client communicating with a NetApp filer
1. Assuming this is your mount command
mount -t nfs -o vers=3 XXX.XXX.XXX.XXX:/myserver/nfs /myclient/nfs
2. And if you are using showmount command from an NFS client and the following are observed
clnt_create: RPC: Program not registered
3. You have to access the NetApp Storage to check the NFS Protocol is enabled. I’m using the Netapp OnCommand System Manager
4. Check that the NFS Client can mount.
showmount --no-headers -e nfs_server / (everyone)
References:
Using nfsstat to troubleshoot NFS performance issues
The write-up is taken from RedHat Using nfsstat and nfsiostat to troubleshoot NFS performance issues on Linux
NFS relies on the existing network infrastructure, any glitches on the network may affect the performance of the connection. One of the tools that can be used is nfsstat
% yum install nfs-utils
The nfsstat command
The nfsstat command displays statistical information about the NFS and Remote Procedure Call (RPC) interfaces to the kernel.
On Server Side,
% nfsstat -s
Server rpc stats: calls badcalls badclnt badauth xdrcall 107310012 0 0 0 0
The most important field to check is the badcalls, which represents the total number of calls rejected by the RPC layer. When the badcalls is greater than 0, than the underlying network needs to be checked, as there might be latency.
On NFS Client Side,
% nfsstat -c
Client rpc stats: calls retrans authrefrsh 23158 0 23172 Client nfs v3: null getattr setattr lookup access readlink 0 0% 7237 31% 7 0% 1443 6% 7874 34% 11 0% read write create mkdir symlink mknod 578 2% 4548 19% 585 2% 1 0% 0 0% 0 0% remove rmdir rename link readdir readdirplus 0 0% 0 0% 0 0% 0 0% 0 0% 51 0% fsstat fsinfo pathconf commit 25 0% 10 0% 5 0% 781 3%
The client is doing well as it has relatively few retransmission requests. If you are encountering excessive retransmissions, you may want to adjust data transfer buffer sizes, which are specified by the mount command options rsize and size.
Check for dropped packets
Check dropped packet by running the following command on both the server and the client:
% nfsstat -o net Client packet stats: packets udp tcp tcpconn 0 0 0 0
NFS mount errors with “clnt_create: RPC: Unknown host” for CentOS 6
When attempting to mount CentOS 6, my mount fails with
clnt_create: RPC: Unknown host
Diagnostic:
If we do a more thorough diagnostic, this is the issue
# showmount -e clnt_create: RPC: Unknown host # showmount -e localhost Export list for localhost: /export/my_data \*
Resolution:
Taken from Redhat Site
Implement forward and reverse lookups (A records and CNAME records) in DNS and have the system point towards the DNS servers. Implement for both IPv4 and IPv6. If unable to resolve DNS issues, change the /etc/hosts file from this:
Change from
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
To
::1 machine_hostname localhost localhost.localdomain localhost6 localhost6.localdomain6
Restart the NFS service and check on the showmount -e localhost and showmount -e and attempt to mount the share.
# service nfs restart # showmount -e localhost # showmount -e
Installing NFS4 on CentOS 5 and 6
For more information on NFS4 and difference between NFS3 and NFS4, do look at A brief look at the difference between NFSv3 and NFSv4.
This tutorial is a guide on how to install NFSv4 on CentOS 5 and 6
Step1: Installing the packages
# yum install nfs-utils nfs4-acl-tools portmap
Some facts about the tools above as given from yum info.
nfs-utils – The nfs-utils package provides a daemon for the kernel NFS server and related tools, which provides a much higher level of performance than the traditional Linux NFS server used by most users.
This package also contains the showmount program. Showmount queries the mount daemon on a remote host for information about the NFS (Network File System) server on the remote host. For example, showmount can display the clients which are mounted on that host. This package also contains the mount.nfs and umount.nfs program.
nfs4-acl-tools – This package contains commandline and GUI ACL utilities for the Linux NFSv4 client.
portmap – The portmapper program is a security tool which prevents theft of NIS (YP), NFS and other sensitive information via the portmapper. A portmapper manages RPC connections, which are used by protocols like NFS and NIS.
The portmap package should be installed on any machine which acts as a server for protocols using RPC.
Step 2: Exports the File System from the NFS Server (Similar to NFSv3 except with the inclusion of fsid=0)
/home 192.168.1.0/24(rw,no_root_squash,sync,no_subtree_check,fsid=0) /install 192.168.1.0/24(rw,no_root_squash,sync,no_subtree_check,fsid=1)
The fsid=0 and fsid=1 option provides a number to use in identifying the filesystem. This number must be different for all the filesystems in /etc/exports that use the fsid option. This option is only necessary for exporting filesystems that reside on a block device with a minor number above 255.one directory can be exported with each fsid option.
Exports the file system
# exportfs -av
Restart the NFS service
# service nfs start
If you are supporting NFSv3, you have to start portmap as NFSv3 requires them. As such, NFSv4 does not need to interact with rpcbind[1], rpc.lockd, and rpc.statd daemons. For more information see Fedora Chapter 9. Network File System (NFS) – How it works for a more in-depth understanding.
# service portmap restart
Step 2: Client Mapping
# mount -t nfs4 192.168.1.1:/ /home
For other information,
