Remote Disk Access with NFS

Transcript Remote Disk Access with NFS

Remote Disk Access with NFS
Vicki Insixiengmay
Jonathan Krieger
NFS Background
Developed inside Sun Microsystems in
early 1980’s
 Based on 2 similar but distinct protocols

– MOUNT  Initial Negotiation between Server and Client
• Determines which file systems are available for mounting
– NFS  Allows Client to Utilize Files in Directory
NFS Description

Network File System(NFS)
– An abbreviation for Network File System, a file format and set of
drivers created by Sun Microsystems Incorporated that allows
DOS/Windows and UNIX applications to share files on disk drives
running under UNIX. NFS relies on remote procedure calls (RPCs)
for communication between clients and servers.

Allows any network user to access disk space over a
networks.
 Incorporates with NIS to access specific file folders
for each user
Important NFS Concepts




Virtual File System (VFS) – transparently and
automatically redirects for mounted files to the server
Remote Procedure Call (RPC) – used for background
mounting of a folder with a file system
Hard Mounting – Continuously trying to remount a file
system
Soft Mounting – Repeated RPC failures cause the
NFS to fail and not hang
Important NFS Daemons
portmap – manages connections for
applications that use the RPC
specification
 nfs – starts necessary RPC processes
 nfslock – allows clients to lock files
within the NFS file system
 netfs – allows processes running on
the client to mount an NFS file system

Installing NFS

RedHat Linux installs NFS by default
– Automatically activated when system boots

To check:
– rpm –qa | grep nfs
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If list is empty, one needs to installed
Configuring NFS on the Server

Needs
– portmap
– nfs
– nfslock
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Correctly configured /etc/exports file
Configuring the /etc/exports file
Main NFS configuration file
 2 columns:

– 1st  Directories made available on the network
– 2nd  Networks or DNS domains that can access
the directories and options

Options include:
– ro, rw, no_root_squash, no_subtree_check, sync
The /etc/exports file
#/etc/exports
/public 134.198.161.101(rw, sync, no_root_squash)
/public 134.198.161.102(rw, sync, no_root_squash)
/public 134.198.161.103(rw, sync, no_root_squash)
/public 134.198.161.104(rw, sync, no_root_squash)
/public 134.198.161.254(rw, sync, no_root_squash)
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NFS Users Control Panel in Linux
Starting NFS on the Server

Configure required daemons
chkconfig –level 35 nfs on
chkconfig –level 35 nfslock on
chkconfig –level 35 portmap on
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Use /etc/init.d to start daemons
service portmap start
service nfs start
service nfslock start

Test NFS
rpcinfo –p localhost
Starting NFS on the Client
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Configure required daemons
chkconfig –level 35 netfs on
chkconfig –level 35 nfslock on
chkconfig –level 35 portmap on

Use /etc/init.d to start daemons
service portmap start
service netfs start
service nfslock start

Test NFS
rpcinfo –p
NFS and DNS
NFS client must have a matching pair of
forward and reverse DNS entries
 DNS lookup on NFS server for IP
address of NFS client must return
server name mapping back to original
IP address

host 134.198.161.103
host 134-198-161-103.research.cs.uofs.edu
NFS Directory Mounting -- Permanent

Insert line into /etc/fstab file
#/etc/fstab
#Directory Mount Point
.103:/public /home
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Type
nfs
Options Dump FSCK
defaults0
0
Create mount directory
mkdir /home
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Mount onto directory into new directory
mount -a
NFS Directory Mounting -- Temporary
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No needed /etc/fstab entry
mkdir /home
ls /home
mount –t nfs 134.198.161.103:/public /home
ls /home
<Listing of Directory>
Deleting a Share

Removing an exported directory from
/etc/exports
 Client Side:
umount /home
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Server Side:
Exportfs –ua
Exportfs -a
Problems

After installing NFS on lab3…
– Lab3  mounted
– Others  NFS on
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Errors
– port 22: No route to host
– Permission denied, server is down
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Firewall Problems
Problems
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Installing NFS on Gateway
– Running FreeBSD
– Inserted into rc.conf file
nfs_client_enable = “YES”
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Source
http://www.freebsd.org/doc/en_US.ISO88591/books/handbook/network-nfs.html
References

www.linuxdocs.org

www.linuxhomenetworking.com
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www.freebsd.org