NFS (Network File System)
NFS (Network File System) is basically developed for sharing
of files and folders between Linux/Unix systems by Sun
Microsystems in 1980. It allows you to mount your local file systems over a
network and remote hosts to interact with them as they are mounted locally on
the same system. With the help of NFS, we can set up file sharing
between Unix to Linux system and Linux to Unix system.
Benefits of NFS
NFS allows local access to remote files.
It uses standard client/server architecture for file sharing
between all *nix based machines.
With NFS it is not necessary that both machines run on the
same OS.
With the help of NFS we can configure centralized
storage solutions.
Users get their data irrespective of physical location.
No manual refresh needed for new files.
Newer version of NFS also supports acl, pseudo root mounts.
Can be secured with Firewalls and Kerberos.
NFS Services
Its a System V-launched service. The NFS server package includes three
facilities, included in the portmap and nfs-utils packages.
portmap : It maps calls made from other machines to the
correct RPC service (not required with NFSv4).
nfs: It translates remote file sharing requests into requests on
the local file system.
rpc.mountd: This service is responsible
for mounting and unmounting of file systems.
Important Files for NFS Configuration
/etc/exports : Its a main configuration file of NFS, all
exported files and directories are defined in this file at the NFS
Server end.
/etc/fstab : To mount a NFS directory on your system across
the reboots, we need to make an entry in/etc/fstab.
/etc/sysconfig/nfs : Configuration file of NFS to control on which
port rpc and other services are listening.
Setup and Configure NFS Mounts on Linux
Server
To setup NFS mounts, well be needing at least two Linux/Unix machines.
Here in this tutorial, Ill be using two servers.
1. NFS Server: nfsserver.example.com with IP-192.168.0.100
2.
NFS Client : nfsclient.example.com with IP-192.168.0.101
Installing NFS Server and NFS Client
We need to install NFS packages on our NFS Server as well as on NFS
Client machine. We can install it via yum (Red Hat Linux) and apt-get
(Debian and Ubuntu) package installers.
[root@nfsserver~]#yuminstallnfsutilsnfsutilslib
[root@nfsserver~]#yuminstallportmap(notrequiredwithNFSv4)
[root@nfsserver~]#aptgetinstallnfsutilsnfsutilslib
Now start the services on both machines.
[root@nfsserver~]#/etc/init.d/portmapstart
[root@nfsserver~]#/etc/init.d/nfsstart
[root@nfsserver~]#chkconfiglevel35portmapon
[root@nfsserver~]#chkconfiglevel35nfson
After installing packages and starting services on both the machines, we need
to configure both the machines for file sharing.
Setting Up the NFS Server
First we will be configuring the NFS server.
Configure Export directory
For sharing a directory with NFS, we need to make an entry in /etc/exports
configuration file. Here Ill be creating a new directory named nfsshare in /
partition to share with client server, you can also share an already existing
directory with NFS.
[root@nfsserver~]#mkdir/nfsshare
Now we need to make an entry in /etc/exports and restart the services to
make our directory shareable in the network.
[root@nfsserver~]#vi/etc/exports
/nfsshare192.168.0.101(rw,sync,no_root_squash)
In the above example, there is a directory in / partition named nfsshare is
being shared with client IP 192.168.0.101 with read and write (rw)
privilege, you can also use hostname of the client in the place of IP in above
example.
NFS Options
Some other options we can use in /etc/exports file for file sharing is as
follows.
ro: With the help of this option we can provide read only
access to the shared files i.e client will only be able to read.
rw: This option allows the client server to
both read and write access within the shared directory.
sync: Sync confirms requests to the shared directory only once
the changes have been committed.
no_subtree_check: This option prevents the subtree checking.
When a shared directory is the subdirectory of a larger file
system, nfs performs scans of every directory above it, in order
to verify its permissions and details. Disabling the subtree check
may increase the reliability of NFS, but reduce security.
no_root_squash: This phrase allows root to connect to the
designated directory.
For more options with /etc/exports, you are recommended to read
the man pages for export.
Setting Up the NFS Client
After configuring the NFS server, we need to mount that shared directory or
partition in the client server.
Mount Shared Directories on NFS Client
Now at the NFS client end, we need to mount that directory in our server to
access it locally. To do so, first we need to find out that shares available on the
remote server or NFS Server.
[root@nfsclient~]#showmounte192.168.0.100
Exportlistfor192.168.0.100:
/nfsshare192.168.0.101
Above command shows that a directory named nfsshare is available at
192.168.0.100 to share with your server.
Mount Shared NFS Directory
To mount that shared NFS directory we can use following mount command.
[root@nfsclient~]#mounttnfs192.168.0.100:/nfsshare/mnt/nfsshare
The above command will mount that shared directory in /mnt/nfsshare on
the client server. You can verify it following command.
[root@nfsclient~]#mount|grepnfs
sunrpcon/var/lib/nfs/rpc_pipefstyperpc_pipefs(rw)
nfsdon/proc/fs/nfsdtypenfsd(rw)
192.168.0.100:/nfsshareon/mnttypenfs(rw,addr=192.168.0.100)
The above mount command mounted the nfs shared directory on to nfs
client temporarily, to mount an NFS directory permanently on your system
across the reboots, we need to make an entry in /etc/fstab.
[root@nfsclient~]#vi/etc/fstab
Add the following new line as shown below.
192.168.0.100:/nfsshare/mntnfsdefaults00
Test the Working of NFS Setup
We can test our NFS server setup by creating a test file on the server end
and check its availability at nfs clientside or vice-versa.
At the nfsserver end
I have created a new text file named nfstest.txt in that shared directory.
[root@nfsserver~]#cat>/nfsshare/nfstest.txt
ThisisatestfiletotesttheworkingofNFSserversetup.
At the nfsclient end
Go to that shared directory in client server and youll find that shared file
without any manual refresh or service restart.
[root@nfsclient]#ll/mnt/nfsshare
total4
rwrr1rootroot61Sep2121:44nfstest.txt
root@nfsclient~]#cat/mnt/nfsshare/nfstest.txt
ThisisatestfiletotesttheworkingofNFSserversetup.
Removing the NFS Mount
If you want to unmount that shared directory from your server after you are
done with the file sharing, you can simply unmount that particular directory
with umount command. See this example below.
root@nfsclient~]#umount/mnt/nfsshare
You can see that the mounts were removed by then looking at the filesystem
again.
[root@nfsclient~]#dfhFnfs
Youll see that those shared directories are not available any more.
Important commands for NFS
Some more important commands for NFS.
showmount -e : Shows the available shares on your local
machine
showmount -e <server-ip or hostname>: Lists the
available shares at the remote server
showmount -d : Lists all the sub directories
exportfs -v : Displays a list of shares files and options on a
server
exportfs -a : Exports all shares listed in /etc/exports, or given
name
exportfs -u : Unexports all shares listed in /etc/exports, or given
name
exportfs -r : Refresh the servers list after
modifying /etc/exports
This is it with NFS mounts for now, this was just a start, Ill come up with
more option and features of NFS in our future articles. Till then, Stay
connected with Tecmint.com for more exciting and interesting tutorials in
future. Do leave your comments and suggestions below in the comment
box.
