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					             NFS


Presented by: mohamad amin Rastgoo




                            Published under Term of GPL
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
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
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
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
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
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
Protocols
   There are several revisions—or protocols—of 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
NFS (Network File System)
   NFS developed by Sun Microsystems
    Native method for file sharing between Unix/Linux
    systems
    Stateless protocol(2&3):
       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
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
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
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
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
Exporting File Systems
   along2.gbdirect.co.uk
   /home/mikeb
   kebab.gbdirect.co.uk
   /mnt/cdrom <anon
   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
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

				
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posted:3/10/2010
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