NFS

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NFS

• Presented by mohamad amin Rastgoo

Published under Term of GPL
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What is file System?

• A disk drive by itself provides a place to store
  data, and nothing more. In fact, by itself, the
  only way to access data on a hard drive is by
  either specifying the data's physical location
  (in terms of cylinder, head, and sector), or by
  its logical location (the
• 65,321st block) on the disk.
• What is needed is a way to more easily keep track
  of things stored on hard drives a way of filling
  information in an easilyaccessible way.
• That is the role of the file system.

Published under Term of GPL
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An Overview of File Systems

• File systems, as the name implies, treat
  different sets of information as files. Each file
  is separate from every other. Over and above the
  information stored within it, each file includes
  additional information
• The file's name
• The file's access permissions
• The time and date of the file's creation,
  access, and modification.
• While file systems in the past have included no
  more complexity than that already mentioned,
  presentday file systems include mechanisms to
  make it easier to group related files together.
  The most commonly used mechanism is the
  directory. Often implemented as a special type of
  file, directories make it possible to create
  hierarchical structures of files and directories.

Published under Term of GPL
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What is NFS?

• As the name implies, the Network File System
  (more commonly known as NFS) is a file system
  that may be accessed via a network connection.
• The Network File System (NFS) was developed to
  allow machines to mount a disk partition on a
  remote machine as if it were on a local hard
  drive. This allows for fast, seamless sharing of
  files across a network With other file systems,
  the storage device must be directly attached to
  the local system. However, with NFS this is not a
  requirement, making possible a variety of
  different configurations, from centralized file
  system servers, to entirely diskless computer
  systems
• However, unlike the other file systems discussed
  here, NFS does not dictate a specific ondisk
  format. Instead, it relies on the server
  operating system's native file system support to
  control the actual I/O to local disk drive(s).
  NFS then makes the file system available to any
  operating system running a compatible NFS client.

Published under Term of GPL
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NFS SAMBA

• Samba uses the SMB protocol to share files and
  printers across a network connection.
• Operating systems that support this protocol
  include Microsoft Windows, OS/2, and Linux
• From a basic point of view, NFS and Samba are
  very similar. Both have a client and server
  application. Both allow a server to share files
  with clients. Both have clients and servers on
  almost every platform. The big difference is the
  Windows PCs have Samba-compatible clients and
  servers as part of their default network support
  and Windows requires third party software to
  support NFS. Conversely, UNIX systems usually
  come with and use NFS by default with Samba being
  used to provide file sharing with Windows PCs.
• SMB is a protocol used by the Microsoft Windows
  operating system to share files on a network. NFS
  is a protocol used primarily on UNIX platforms
  for sharing

Published under Term of GPL
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Why Use NFS?

• NFS is useful for sharing directories of files
  between multiple users on the same network.
• For example, a group of users working on the same
  project can have access to the files for that
  project using a shared directory of the NFS file
  system (commonly known as an NFS share) mounted
  in the directory /myproject. To access the shared
  files, the user goes into the /myproject
  directory on his machine. There are no passwords
  to enter or special commands to remember. Users
  work as if the directory is on their local machine

Published under Term of GPL
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Useful usage

• It can be used for Networked Backups
• The theory of NFS backup is relatively simple
  mount each host to the NFS
• server, write a .tar backup script, and check
  that the following permission
• sets conform on both machines
• 1. Read Write access.
• 2. Mount permissions.
• 3. GID/UID.

Published under Term of GPL
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Protocols

• There are several revisionsor protocolsof NFS.
  Version 3 of NFS (NFSv3) is rapidly becoming the
  default version on most Linux systems. This
  version is available in the latest Linux 2.2 and
  2.4 kernels
• Version 4 in under develop and going to remove
  lacks
• NFS Versions 2 and 3 are stateless protocols, but
  NFS Version 4 introduces state.
• NFS Version 4 introduces support for byterange
• locking and share reservation.
• NFS Version 4 introduces file delegation.
• NFS Version 4 uses compound RPCs.
• NFS Version 4 specifies a number of sophisticated
  security mechanisms, and mandates their
  implementation by all conforming clients.
• NFS Version 4 standardizes the use and
  interpretation of ACLs across Posix and Windows
  environments.
• NFS Version 4 combines the disparate NFS
  protocols (stat, NLM, mount, ACL,
• and NFS)
• NFS Version 4 introduces protocol support for
  file migration and replication.
• NFS Version 4 requires support of RPC over
  streaming network transport
• protocols such as TCP.
• For more information on the NFS Version 4
  protocol, read RFC 3530.

Published under Term of GPL
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NFS (Network File System)

• NFS developed by Sun Microsystems
• Native method for file sharing between
  Unix/Linux systems
• Stateless protocol(23)
• Means server keeps no state
• Renders server crashes easily recoverable
• Should be compatible with all Unix like systems
• Best in trusted environment, not highly secure
• Best where all user/group IDs are same
• Often used with Information Services (NIS) to
  synchronise user/group IDs

Published under Term of GPL
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NFS (Network File System)

• Systems are clients, servers or both
• Clients import shared filesystems
• Servers export shared filesystems
• Servers easy to implement via network daemons
• Clients require kernel modifications
• Linux systems normally work as both already
• NFS is NOT Unix/Linux specific (e.g. PCNFS)

Published under Term of GPL
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Exporting File Systems

• Exporting handled by daemons .nfsd and Must be
  running for NFS export to work
• Exported file systems listed in /etc/exports,
  format is
• hostname(flags) hostname(flags)
• Example
• /tmp .blah.co.uk(ro)
• Exports /tmp to all systems belonging to domain
  read only J1
• Important flags
• (read only)
• (read/write)

Published under Term of GPL
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Exporting File Systems

• _squash (map all uid/gid to something)
• (specify user ID to map to)
• (specify group ID to map to)
• After changing /etc/exports, restart NFS
• killall -HUP rpc.nfsd
• killall -HUP mount
• or
• /etc/rc.d/init.d/nfs restart

Published under Term of GPL
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Viewing exports

• ? Use showmount
• showmount -e
• showmount -e hostname
• Export list for
• landlord.gbdirect.co.uk
• /usr/local/gbdirect/cvsroot
• roti.gbdirect.co.uk
• /home/adamg
• roti.gbdirect.co.uk
• /home/andylong

Published under Term of GPL
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Exporting File Systems

• along2.gbdirect.co.uk
• /home/mikeb
• kebab.gbdirect.co.uk
• /mnt/cdrom
• clnt
• ? uses a to handle requests
• ? This must be running (and you must have access
  to it) to use
• ? Check that hosts.allow contains an entry to
  permit you access, e.g.
• ? ALL or
• ? my.ip.network.

Published under Term of GPL
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Importing File Systems

• Mount a remotely exported directory Usually have
  to be superuser
• mount
• hostname/sharename /local/directory
• If successful, the export named /sharename on
  host hostname is mounted on
• our mountpoint /local/directory Files accessed
• just as if local Remote host must be exporting
  the directory
• You must have access permission
• Your local mountpoint must exist
• Exactly like mounting a device

Published under Term of GPL