Network Information Services NIS

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Network Information Services (NIS)

• Linux tutorial

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What is NIS?

• Problems in running a distributed computing
  environment
• Each Workstations has its own copies of common
  configuration files such as passwd, group, and
  hosts files
• These files must be consistent and every changes
  to these common files much be propagated to every
  hosts on the network

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What is NIS?
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What is NIS?

• The NIS, released by Sun in 1980s, was the first
  prime time administrative database to address
  these problems.
• It was originally called the Sun Yellow Pages,
  but eventually had to be renamed for legal
  reasons. Many vendors have licensed Suns code,
  making NIS the most widely-supported network
  database system

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What is NIS?

• It is a distributed database system that replaces
  copies of commonly replicated configuration files
  with a centralized management facility
• Instead of having to manage each hosts files,
  you maintain one database for each file on one
  central server

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NIS Masters, Slaves, and Clients
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NIS Servers

• An NIS server is a machine storing a set of maps
  that are available to network machines and
  applications.
• NIS master server
• contains the set of maps that you, the NIS
  administrator, create and update as necessary.
• Each NIS domain must have one, and only one,
  master server.

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NIS Servers

• NIS Slave server
• A slave server has a complete copy of the master
  set of NIS maps. Whenever the master server maps
  are updated, the updates are propagated among the
  slave servers. The existence of slave servers
  allows the system administrator to evenly
  distribute the load resulting from answering NIS
  requests. It also minimizes the impact of a
  server becoming unavailable.

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NIS Elements

• NIS Domains
• An NIS domain is a collection of machines that
  share a common set of NIS maps. Each domain has a
  domain name and each machine sharing the common
  set of maps belongs to that domain.
• Domain names are case-sensitive.

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NIS Elements

• NIS Maps
• NIS maps are essentially two-column tables. One
  column is the key and the other column is
  information value related to the key. NIS finds
  information for a client by searching through the
  keys. Some information is stored in several maps
  because each map uses a different key.

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NIS Elements

• For example, the names and addresses of machines
  are stored in two maps hosts.byname and
  hosts.byaddr. When a server has a machine's name
  and needs to find its address, it looks in the
  hosts.byname map. When it has the address and
  needs to find the name, it looks in the
  hosts.byaddr map.

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NIS Elements

• Maps for a domain are located in each server's
  /var/yp/domainname directory.
• For example, the maps that belong to the domain
  test.com are located in each server's
  /var/yp/test.com directory.
• An NIS Makefile is stored in the /var/yp
  directory of machines designated as a NIS server
  at installation time. Running make in that
  directory causes makedbm to create or modify the
  default NIS maps from the input files.

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NIS Elements

• NIS daemons

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NIS Query
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NIS Query
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Basic NIS Management

• Installing a new NIS Environment, building Master
  and slave servers
• Starting the ypserv daemon, which enables the
  system to act as NIS Server
• Adding new slave servers when growth of your
  network
• Modifying the clients administrative files
• Starting the ypbind daemon, allowing the client
  to make NIS requests

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Building NIS Master Server

• Edit /etc/defaultdomain to enter your NIS domain
  name
• Edit /etc/rc.d/rc.inet2, modify
• if -r /etc/defaultdomain then
• nisdomainname cat /etc/defaultdomain
• fi
• into
• if -r /etc/defaultdomain then
• /bin/ypdomainname cat /etc/defaultdomain
• fi

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Building NIS Master Server

• Add the following lines
• dname/bin/ypdomainname
• echo "NIS domainname is dname"
• echo -n "starting NIS services"
• /usr/sbin/ypserv
• echo -n " ypserv"
• echo "running rpc.yppasswdd"
• /usr/sbin/rpc.yppasswdd -p /etc/passwd.yp

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Building NIS Master Server

• Last, UNCOMMENT the following lines
• if -d /var/yp then
• echo "Running ypbind..."
• /usr/sbin/ypbind
• fi
• This made the NIS master as client

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Building NIS Master Server

• Prepare the passwd file for use by NIS
• Our Linux is using shadow password but using
  shadow passwords alongside NIS does not make too
  much senses, so we will put only root and system
  passwords in the local shadow map on the local
  host. For all the normal user you have a normal
  passwd map with passwords distributed trough NIS.

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Building NIS Master Server

• NIS Masters as clients
• Provide restricted access to the NIS Server
• The server has its own passwd file. An alternate
  passwd map source file which is network wide is
  used
• In the tutorial, we dont need this extra
  security but it is required to work around the
  shadow passwd issue

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Building NIS Master Server
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Enabling NIS on client

• Make sure that configuration files on the client
  includes NIS marker entries so that NIS map
  information will be added to the local files
• append to /etc/passwd, /etc/shadow and
  /etc/group
• Set the NIS domain name, edit /etc/defaultdomain

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Enabling NIS on client

• Start the ypbind daemon, which is responsible for
  locating NIS servers and maintaining bindings of
  domain names to servers

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Changing Password in NIS

• Why you need to wait sometime for your new
  password to be effective if you change your
  password in our Lab??

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Changing Password in NIS
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Merits of NIS

• Simple, easy to understand. Its analogous to
  copying files around in most cases, its
  unnecessary for administrators to be aware of
  NIS internal data formats
• Widely supported by multiple vendors like DEC,
  HP, SGI.

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Problems of NIS

• Storing each type of information in separate data
  files (eg host info and user info) resulted in
  problems propagating the information
• When a master server updated its slaves, each of
  these files, if changed, was sent over the
  network. In environments with hundred of hosts
  and thousand of users, this update could take a
  while

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Problems of NIS

• Between updates, slave servers contained
  out-of-dated information.
• Predefined operations limited information
  retrieval.
• For instance, only the users log-in named and
  uid were indexed, making database searching by
  full user name imossible

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Problems of NIS

• NIS was not a true database. It did not support
  atomic operations, undo of changes, or logging of
  operations.
• Finally, there was no easy way to manage it. To
  change data in the database, the static file had
  to be modified, reconverted into a database, and
  loaded into the server

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Network File System (NFS)

• Linux tutorial

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What is NFS?

• The Network File System, allows you to share
  filesystems among computers.
• NFS is almost transparent to users and is
  stateless.
• NFS was introduced by Sun in 1985. It was
  originally implemented as a surrogate filesystem
  for diskless clients.

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What is NFS?

• NFS support has been implemented on many
  platforms ranging from the MS-DOS to the VMS
  operating systems. Many use code licensed from
  Sun.

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What is NFS?

• The NFS environment can be implemented on
  different operating systems because it defines an
  abstract model of a file system, rather than an
  architectural specification. Each operating
  system applies the NFS model to its file system
  semantics. This means that file system operations
  like reading and writing function as though they
  are accessing a local file.

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Benefits of NFS

• Allows multiple computers to use the same files,
  so everyone on the network can access the same
  data
• Reduces storage costs by having computers share
  applications instead of needing local disk
  space for each user application
• Provides data consistency and reliability because
  all users can read the same set of files
• Makes mounting of file systems transparent to
  users

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Benefits of NFS

• Makes accessing remote files transparent to users
• Supports heterogeneous environments
• Reduces system administration overhead

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NFS Elements
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Setting up NFS

• Start mountd and nfsd
• edit /etc/rc.d/rc.inet2 file and uncomment
• Start the various SUN RPC servers.
• if -f NET/rpc.portmap then
• Start the NFS server daemons.
• if -f NET/rpc.mountd then
• echo -n " mountd"
• NET/rpc.mountd
• fi
• if -f NET/rpc.nfsd then
• echo -n " nfsd"
• NET/rpc.nfsd
• fi

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Setting up NFS

• Export filesystems, edit /etc/exports
• See exports(5) for a description.
• This file contains a list of all directories
  exported to other computers.
• It is used by rpc.nfsd and rpc.mountd.
• /home linux-1b (rw)
• This file servers as the access control list for
  file systems which may be exported to NFS
  clients. See man pages of exports(5) for a lists
  of the options

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Hard and Soft Mounts

• Hard mount
• If a server goes down, make operations that try
  to access it block until the server comes back up
• Soft mount
• If a serve goes down, make operations that try to
  access it fail and return an error. This is
  useful to avoid processes hanging on
  inessential mounts

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Hard and Soft Mounts

• How to choose hard/soft mounts
• You never want to write data to an unreliable
  device, nor do you want to try to load
  executables from it. You should not use the soft
  mount on any filesystem that is writeable, nor on
  any filesystem from which you load executables.
  NFS only guarantees the consistency of data after
  a server crash if the NFS filesystem was
  hardmounted

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NFS Shortcomings

• NFS Suffers its greatest performance troubles
  because of its stateless design
• Since the client assumes a write operation is
  complete once it receives an acknowledgment from
  the server, servers must commit each modified
  block to disk before replying, to avoid
  discrepancies in the event of a crash. This
  introduces a significant delay in NFS writes
• In contrast, some OS (Like Netware) will
  acknowledge the client before committing the
  writes.

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Installation Configuration of XFree86

• Linux tutorial

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What is XFree86?

• XFree86 is a freely redistributable port of the
  MIT X window System version 11, release 6(X11R6)
  for all x86 UNIX implementations. It includes all
  of the required binaries, support files,
  libraries and tools
• More information can be found in
  http//www.xfree86.org

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Latest XFree86 release

• The current version of XFree86 is v3.3.2. It
  supports most-up-todate video chipsets like
• ATI Rage Pro (AGP), Matrox Millennium II AGP,
  Number Nine Revolution 3D, Tseng ET6100, S3
  ViRGE/MX and ViRGE/GX2.
• The XFree86 comes with the Slackware distribution
  is v3.3.1

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Installation of XFree86

• Install XFree86 by running setup. Select diskset
  of X, XAP and XV

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Installation of XFree86

• Select 16-color generic X Server and the
  appropriate X Server for your video chipset

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Configuration of XFree86

• Run XF86Setup to start the setup program. This
  program will walks you through a series of
  configuration panels. The whole process is quite
  painless

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Configuration of XFree86

• Next you need to configure the mouse.
• You should pay attention to the mouse type
  Microsoft, ps/2 and ports they connected to

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Configuration of XFree86

• Keyboard is easy to configure. Just choose the
  default setting should be OK

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Configuration of XFree86

• Configure the card you used is the most
  important. Be sure you have installed the
  corresponding X Server of your card

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Configuration of XFree86

• Configure the horizontal sync and vertical sync
  of your monitor. You can find this information in
  your monitors manual

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Advanced Configuration of XFree86

• The XF86Setup actually create a X configuration
  file for you at /etc/XF86Config
• We will take a look on various sections of this
  Config file.

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Advanced Configuration of XFree86

• The Pointer section
• Section "Pointer"
• Protocol "Microsoft"
• Device "/dev/mouse"
• When using XQUEUE, comment out the above two
  lines, and uncomment
• the following line.
• Protocol "Xqueue"
• Baudrate and SampleRate are only for some
  Logitech mice
• BaudRate 9600
• SampleRate 150
• Emulate3Buttons is an option for 2-button
  Microsoft mice
• Emulate3Timeout is the timeout in milliseconds
  (default is 50ms)
• Emulate3Buttons

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Advanced Configuration of XFree86

• The Monitor Section
• Section "Monitor"
• Identifier "Eizo"
• VendorName "Unknown"
• ModelName "Unknown"
• HorizSync is in kHz unless units are specified.
• HorizSync 31.5 - 82.0
• VertRefresh may be a comma separated list of
  discrete values, or a
• VertRefresh 40-150

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Advanced Configuration of XFree86

• The screen section
• Section "Screen"
• Driver "accel"
• Device "WinFast S3"
• Monitor "Eizo"
• DefaultColorDepth 16
• Subsection "Display"
• Depth 8
• Modes "640x480" "800x600"
  "1024x768" "1280x1024"
• ViewPort 0 0
• EndSubsection
• Subsection "Display"
• Depth 16
• Modes "1024x768" "800x600"
• ViewPort 0 0
• Virtual 1024 768
• EndSubsection

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Advanced Configuration of XFree86

• See man page of XF86Config
• See README files of separate video chipsets