Mount nfs share from linux

How To Mount NFS Share In Linux and Windows?

Network File System or NFS is a network-based filesystem protocol which is mainly used to share files and folders over the network. NFS is a UNIX based technology but can be used by most of the operating systems like Linux, Ubuntu, Debian, Kali, Mint, Fedora, CentOS, RedHat and Windows operating systems Windows 7, Windows 8, Windows 10, Windows Server 2008, Windows Server 2012, Windows Server 2016.

Install NFS Server

NFS packages mainly divided into two parts. First is the server side packages which will install related kernel modules and server tools.

Ubuntu, Debian, Mint, Kali Client Packages

Fedora, CentOS, Fedora Client Packages

Ubuntu, Debian, Mint, Kali Server Packages

After the installation is complete the nfs-server service will be also created automatically.

Fedora, CentOS, Fedora Server Packages

Check NFS Service Status

As the NFS shares will be served over nfs-server we need to the if it is working. We will use systemctl status command with the nfs-server service name.

Check NfS Service Status

We can see that the service is active and working properly.

Start NFS Service

If the service is not started or stopped in any way we need to start the nfs-server service. We will use systemctl start command with the nfs-server service name like below.

Create NFS Share

NFS main configuration is stored in the /etc/exports file. Each share is created line by line. For example, if we want to share /mnt with the IP address 192.168.10.10 we will use the following configuration.

But generally, we share the files and folders with everyone who has access to the NFS server. We can use the following configuration to share everyone.

Enable Exports

After creating the share configuration we need to refresh the NFS table where the shares are stored. We can simply use exportfs command with the -a option which will add current configuration to the NFS table.

Mount NFS Share For Linux

We can use mount command in order to mount NFS share. We will specify the filesystem type as nfs to the mount command with the -t option like below. The server IP address is 192.168.142.144 and share is /mnt . We will mount to the /home/ismail/poftut1 .

List NFS Mounts

After mounting the NFS share we can check it by listing the NFS mount. We will use mount command and filter NFS shares with the grep command like below.

List NFS Mounts

Unmount NFS Share For Linux

We can unmount already mounted NFS shares with the umount command. We will just specify the mount path to the umount command with the sudo command like below.

Mount NFS Share For Windows

First, we will enable NFS modules or features on Windows operating systems. Open Start > Control Panel > Programs. Select Turn Windows Features on or off. Select Services for NFS. Click OK.

We can mount NFS shares in Windows operating systems too. We will use mount command. We will also provide nolock option and other parameters like remote NFS server IP address and local drive which is Z in this case.

Alternatively, we can use net use command which can also mount NFS shares. We will provide the partition name which is z and remote NFS server.

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Mount nfs share from linux

Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed.

Contents

Installation

Both client and server only require the installation of the nfs-utils package.

It is highly recommended to use a time synchronization daemon to keep client/server clocks in sync. Without accurate clocks on all nodes, NFS can introduce unwanted delays.

Configuration

Server

Global configuration options are set in /etc/nfs.conf . Users of simple configurations should not need to edit this file.

The NFS server needs a list of exports (see exports(5) for details) which are defined in /etc/exports or /etc/exports.d/*.exports . These shares are relative to the so-called NFS root. A good security practice is to define a NFS root in a discrete directory tree which will keep users limited to that mount point. Bind mounts are used to link the share mount point to the actual directory elsewhere on the filesystem.

Consider this following example wherein:

1. The NFS root is /srv/nfs .
2. The export is /srv/nfs/music via a bind mount to the actual target /mnt/music .

To make the bind mount persistent across reboots, add it to fstab:

Add directories to be shared and limit them to a range of addresses via a CIDR or hostname(s) of client machines that will be allowed to mount them in /etc/exports , e.g.:

It should be noted that modifying /etc/exports while the server is running will require a re-export for changes to take effect:

To view the current loaded exports state in more detail, use:

For more information about all available options see exports(5) .

Starting the server

Restricting NFS to interfaces/IPs

By default, starting nfs-server.service will listen for connections on all network interfaces, regardless of /etc/exports . This can be changed by defining which IPs and/or hostnames to listen on.

Restart nfs-server.service to apply the changes immediately.

Firewall configuration

To enable access through a firewall, TCP and UDP ports 111 , 2049 , and 20048 may need to be opened when using the default configuration; use rpcinfo -p to examine the exact ports in use on the server:

When using NFSv4, make sure TCP port 2049 is open. No other port opening should be required:

When using an older NFS version, make sure other ports are open:

To have this configuration load on every system start, edit /etc/iptables/iptables.rules to include the following lines:

The previous commands can be saved by executing:

If using NFSv3 and the above listed static ports for rpc.statd and lockd the following ports may also need to be added to the configuration:

To apply changes, Restart iptables.service .

Enabling NFSv4 idmapping

This article or section needs expansion.

The NFSv4 protocol represents the local system’s UID and GID values on the wire as strings of the form user@domain . The process of translating from UID to string and string to UID is referred to as ID mapping. See nfsidmap(8) for details.

Even though idmapd may be running, it may not be fully enabled. If /sys/module/nfs/parameters/nfs4_disable_idmapping or /sys/module/nfsd/parameters/nfs4_disable_idmapping returns Y on a client/server, enable it by:

Set as module option to make this change permanent, i.e.:

To fully use idmapping, make sure the domain is configured in /etc/idmapd.conf on both the server and the client:

See [2] for details.

Client

Users intending to use NFS4 with Kerberos need to start and enable nfs-client.target .

Manual mounting

For NFSv3 use this command to show the server’s exported file systems:

For NFSv4 mount the root NFS directory and look around for available mounts:

Then mount omitting the server’s NFS export root:

If mount fails try including the server’s export root (required for Debian/RHEL/SLES, some distributions need -t nfs4 instead of -t nfs ):

Mount using /etc/fstab

Using fstab is useful for a server which is always on, and the NFS shares are available whenever the client boots up. Edit /etc/fstab file, and add an appropriate line reflecting the setup. Again, the server’s NFS export root is omitted.

Some additional mount options to consider:

rsize and wsize The rsize value is the number of bytes used when reading from the server. The wsize value is the number of bytes used when writing to the server. By default, if these options are not specified, the client and server negotiate the largest values they can both support (see nfs(5) for details). After changing these values, it is recommended to test the performance (see #Performance tuning). soft or hard Determines the recovery behaviour of the NFS client after an NFS request times out. If neither option is specified (or if the hard option is specified), NFS requests are retried indefinitely. If the soft option is specified, then the NFS client fails a NFS request after retrans retransmissions have been sent, causing the NFS client to return an error to the calling application.

Mount using /etc/fstab with systemd

Another method is using the x-systemd.automount option which mounts the filesystem upon access:

To make systemd aware of the changes to fstab, reload systemd and restart remote-fs.target [3].

The factual accuracy of this article or section is disputed.

As systemd unit

Create a new .mount file inside /etc/systemd/system , e.g. mnt-myshare.mount . See systemd.mount(5) for details.

What= path to share

Where= path to mount the share

Options= share mounting options

To use mnt-myshare.mount , start the unit and enable it to run on system boot.

automount

To automatically mount a share, one may use the following automount unit:

Disable/stop the mnt-myshare.mount unit, and enable/start mnt-myshare.automount to automount the share when the mount path is being accessed.

Mount using autofs

Using autofs is useful when multiple machines want to connect via NFS; they could both be clients as well as servers. The reason this method is preferable over the earlier one is that if the server is switched off, the client will not throw errors about being unable to find NFS shares. See autofs#NFS network mounts for details.

Tips and tricks

Performance tuning

When using NFS on a network with a significant number of clients one may increase the default NFS threads from 8 to 16 or even a higher, depending on the server/network requirements:

It may be necessary to tune the rsize and wsize mount options to meet the requirements of the network configuration.

In recent linux kernels (>2.6.18) the size of I/O operations allowed by the NFS server (default max block size) varies depending on RAM size, with a maximum of 1M (1048576 bytes), the max block size of the server will be used even if nfs clients requires bigger rsize and wsize . See https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/5.8_Technical_Notes/Known_Issues-kernel.html It is possible to change the default max block size allowed by the server by writing to the /proc/fs/nfsd/max_block_size before starting nfsd. For example, the following command restores the previous default iosize of 32k:

To make the change permanent, create a systemd-tmpfile:

To mount with the increased rsize and wsize mount options:

Furthermore, despite the violation of NFS protocol, setting async instead of sync or sync,no_wdelay may potentially achieve a significant performance gain especially on spinning disks. Configure exports with this option and then execute exportfs -arv to apply.

Automatic mount handling

This trick is useful for NFS-shares on a wireless network and/or on a network that may be unreliable. If the NFS host becomes unreachable, the NFS share will be unmounted to hopefully prevent system hangs when using the hard mount option [5].

Make sure that the NFS mount points are correctly indicated in fstab:

Create the auto_share script that will be used by cron or systemd/Timers to use ICMP ping to check if the NFS host is reachable:

in the auto_share script above.

Make sure the script is executable.

Next check configure the script to run every X, in the examples below this is every minute.

systemd/Timers

Finally, enable and start auto_share.timer .

Using a NetworkManager dispatcher

NetworkManager can also be configured to run a script on network status change.

The easiest method for mount shares on network status change is to symlink the auto_share script:

However, in that particular case unmounting will happen only after the network connection has already been disabled, which is unclean and may result in effects like freezing of KDE Plasma applets.

The following script safely unmounts the NFS shares before the relevant network connection is disabled by listening for the pre-down and vpn-pre-down events, make the script is executable:

Create a symlink inside /etc/NetworkManager/dispatcher.d/pre-down to catch the pre-down events:

Troubleshooting

There is a dedicated article NFS/Troubleshooting.

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Beginners guide to mount NFS share in Linux with examples

Table of Contents

In this tutorial I will share the steps to mount NFS share on the client nodes

Overview on NFS

• The Network File System (NFS) is a distributed file system that provides transparent access to remote disks
• Instead of duplicating common directories such as /usr/local on every system, NFS provides a single copy of the directory that is shared by all systems on the network.
• For the user, NFS means that he or she doesn’t have to log into other systems to access files.
• An NFS server is a host that owns one or more filesystems and makes them available on the network;
• NFS clients mount filesystems from one or more servers.

Pre-requisites

Setup NFS exports Server

Configuring NFS Server is not covered as part of this article so I will assume you already a NFS server up and running. In this article we will only cover the NFS client part i.e. to mount NFS share on the client from the server.

In this example I have setup nfs exports on server1 (10.43.138.1) with below configuration

Install NFS Client

The NFS client package will vary based on the Linux distribution.

On Ubuntu install nfs-common

On RHEL/CentOS environment install nfs-utils

Mount NFS File System manually

You can use mount command to mount the NFS file system form remote server to your localhost. The syntax to mount NFS File System on the client node would be:

As per our configuration

• NFS_SERVER is server1 (10.43.138.1)
• /PATH/TO/EXPORTED/DIR is /ISS
• /MOUNT_POINT_ON_CLIENT is /tmp/logs

So to mount NFS manually we will execute below command on the client i.e. server2 (10.43.138.2)

We need the mount point, so I will create the mount point

Next mount the NFS file system from server1 on server2

Verify if the NFS FS is mounted properly

Now based on the permission of your NFS share you can access the data of /ISS from server1 on /tmp/logs on server2

Mount NFS File System Persistently

Now with mount command the changes are not persistent and will not survive a reboot. So if you wish to mount your NFS File System after every reboot then you must add this in /etc/fstab or create a systemd unit file to update fstab during reboot.

In this article we will use our traditional fstab to auto-mount the file system. First of all make sure your mount point exists

Next update /etc/fstab with below content

Save and exit the file.

Next to verify if this is working, first un-mount the NFS File System (if in mounted state)

Now we will use fstab to mount all the FS available in /etc/fstab . You can safely execute this command and it will not break anything in your environment

Now verify if your NFS File System is properly mounted:

That’s it so next time your client reboots, the NFS File System will be automatically mounted as long as your NFS server is up and running.

Additional Options to mount NFS File System

This section will be applicable based on your NFS server configuration.

For example in the above case if I check for the options using which NFS was mounted

Here this command tells us that the NFS was mounted using NFSv4 with different rsize , wsize etc. So while performing the mount we have an option to modify these values.

Provide NFS version while mounting the NFS File System

If your NFS server allows you to choose a NFS version for the client mount then you can use -o nfsvers= , for example to mount using NFSv3

Similarly if your client and server supports you can provide different NFS version.

Setting Block Size to Optimize Transfer Speeds

The mount command options rsize and wsize specify the size of the chunks of data that the client and server pass back and forth to each other. If no rsize and wsize options are specified, the default varies by which version of NFS we are using.

Removing NFS Mounts from the Client

To un-mount the NFS mount point you can just use umount command followed by the mount point path

OR if you are not aware of the mount point you can also provide the REMOTE_SERVER and REMOTE_DIR PATH i.e.

So in our example to un-mount our NFS File System we will use

Next use df or mount command to make sure the NFS FS is not mounted any more.

How to fix «umount: device is busy»

It is possible sometimes you may get this error

This is most likely because the mount_point on which your NFS file system is mounted is in use by some process. So either you can find and kill that process or let the process complete.

Kill the process

To kill the process first you should know the process which is occupying the mount_point . You can use

This will give you the PID of the process using the mount_point in below format, in this example my mount_point is /mnt :

So now you can search for process with PID 12594

Now since you know the process which is occupying your NFS mount point, you can either choose to kill it or let the process complete

You can also use lsof to detect the list of process using a file system:

Lazy un-mount

If you choose to ignore the PID and want to let it complete, how would you know when the process is complete?

You will have to constantly monitor the PID to make sure it is complete after which only you can un-mount your NFS File System. SO to overcome this we have something called lazy un-mount where we can trigger umount with -l or —lazy , for example:

The default umount is not working so let’s try lazy un-mount

The exit status is success so our command was executed successfully:

So this will detach the file system from the file system hierarchy now, and cleanup all references to the file system as soon as it is not busy anymore. The recommended use-case for umount -l is to prevent hangs on shutdown due to an unreachable network share where a normal umount will hang due to a downed server or a network partition.

Conclusion

In this tutorial we learned about methods to mount NFS shares on client nodes. You can use these steps across different Linux distributions such as Red Hat, Fedora, CentOS, SuSE, Ubuntu, Debian etc. The only difference would be the NFS client package to be installed.

Lastly I hope the steps from the article to mount NFS on Linux was helpful. So, let me know your suggestions and feedback using the comment section.

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