Remote Disk Access with NFS

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Remote Disk Access with NFS

• Vicki Insixiengmay
• Jonathan Krieger

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NFS Background

• Developed inside Sun Microsystems in early 1980s
• 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

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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

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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

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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

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Installing NFS

• RedHat Linux installs NFS by default
• Automatically activated when system boots
• To check
• rpm qa grep nfs
• If list is empty, one needs to installed

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Configuring NFS on the Server

• Needs
• portmap
• nfs
• nfslock
• Correctly configured /etc/exports file

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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

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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)
• NFS Users Control Panel in Linux

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Starting NFS on the Server

• Configure required daemons
• chkconfig level 35 nfs on
• chkconfig level 35 nfslock on
• chkconfig level 35 portmap on
• Use /etc/init.d to start daemons
• service portmap start
• service nfs start
• service nfslock start
• Test NFS
• rpcinfo p localhost

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Starting NFS on the Client

• 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

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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

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NFS Directory Mounting -- Permanent

• Insert line into /etc/fstab file
• /etc/fstab
• Directory Mount Point Type Options Dump FSCK
• .103/public /home nfs defaults 0 0
• Create mount directory
• mkdir /home
• Mount onto directory into new directory
• mount -a

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NFS Directory Mounting -- Temporary

• No needed /etc/fstab entry
• mkdir /home
• ls /home
• mount t nfs 134.198.161.103/public /home
• ls /home
• ltListing of Directorygt

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Deleting a Share

• Removing an exported directory from /etc/exports
• Client Side
• umount /home
• Server Side
• Exportfs ua
• Exportfs -a

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Problems

• After installing NFS on lab3
• Lab3 ? mounted
• Others ? NFS on
• Errors
• port 22 No route to host
• Permission denied, server is down
• Firewall Problems

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Problems

• Installing NFS on Gateway
• Running FreeBSD
• Inserted into rc.conf file
• nfs_client_enable YES
• Source
• http//www.freebsd.org/doc/en_US.ISO8859-1/books/h
  andbook/network-nfs.html

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References

• www.linuxdocs.org
• www.linuxhomenetworking.com
• www.freebsd.org