The Network Information System

1
The Network Information System

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• Chunqing Yuan Weiwei Huang
• For CpE473

Local Area Network
2
Introduction

• What is NIS?
• Sun introduced Network Information System (NIS),
  formerly called Yellow Pages, or YP
• provides a mechanism for keeping important files
  synchronized between hosts on a network
• What does NIS do?
• allows networked machines to have a common
  interface regardless of the workstation that you
  log into
• allows you to coordinate the distribution of
  database information throughout your networked
  environment
• focused on making network administration more
  manageable by providing centralized control over
  a variety of network information

3
Systems support for NIS

• --------------------------------------------------
  -------------------------
• System Supports NIS?
• --------------------------------------------------
  -------------------------
• Solaris Partially
• HP-UX Yes
• IRIX Yes
• SunOS Yes
• OSF/1 Yes
• BSDI No
• --------------------------------------------------
  -------------------------

4
Advantages and Disadvantages of NIS

• Advantage
• unnecessary for administrators to be aware of
  NISs internal data formats
• Disadvantages
• not suitable for managing a large network of
  machines
• consume a fair amount of network bandwidth
• If a slave server is down or inaccessible when a
  map is changed, the slaves copy will not be
  updated
• not secure

5
The NIS Environment

• NIS uses a client-server arrangement.
• Systems can have the following roles
• Master server -- A system that stores the master
  copy of the NIS database files, or maps. Only the
  master maps can be modified, whereas slave
  servers provide read-only access. Each domain can
  have only one master server.
• Slave server -- A system that obtains and stores
  copies of the master server's NIS maps. Each
  domain can have multiple slave servers
  distributed throughout the network.
• Client -- Any system that
• queries NIS servers for NIS
• database information. Clients
• do not store and maintain
• copies of the NIS maps for
• their domain locally.

6
NIS Maps

• Information distributed by NIS is stored in
  database files called maps
• Most of the NIS maps represent files that were
  traditionally stored in the /etc directory,
  include the following
• aliases passwd
• group protocols
• hosts rpc
• netgroups services
• networks
• Each NIS map contains a set of keys and
  associated values. Each NIS map has a map name,
  used by programs to access data in the map.

7
NIS Domains

• A named set of NIS maps is called a domain.
• A domain name is required for retrieving data
  from an NIS database. It is set at the time the
  system is booted
• An NIS domain is an administrative entity
• that consists of a master server, one or more
• slave servers, and numerous clients
• All systems in a domain share the same set of
• NIS database files
• NIS uses domains to arrange the workstations,
  users, and networks in its namespace.

8
NIS Data Storage

• The data in NIS maps is stored as databases in
  dbm/ndbm, btree, or hash format
• Each NIS map is stored as a pair of ndbm files,
  one called map.dir and the other called map.pag,
  in a subdirectory of the NIS directory named for
  the NIS domain
• For example, the NIS map for the /etc/hosts file
  in the domain market might be stored in these
  dbm/ndbm files
• /var/yp/market/hosts.byaddr.dir
• /var/yp/market/hosts.byaddr.pag
• /var/yp/market/hosts.byname.dir
• /var/yp/market/hosts.byname.pag

9
Selected NIS commands and daemons

• --------------------------------------------------
  --------------------------------------------------
  --------------------------------
• Program Description
• --------------------------------------------------
  --------------------------------------------------
  --------------------------------
• ypserv NIS server daemon, started at boot time
• ypbind NIS client daemon, started at boot time
• domainname Sets the NIS domain a machine is in
  (run at boot time)
• ypxfrd Serves requests from ypxfr (runs on
  master server)
• makedbm Builds an ndbm map from a flat file
• ypmake Rebuilds ndbm maps from flat files that
  have changed
• ypinit Configures a host as a master or slave
  server
• ypset Makes ypbind connect to a particular
  server
• ypwhich Finds out which server the current host
  is using
• ypmatch Prints map entries for a specified key
• yppasswd Changes a password on the NIS master
  server
• ypupdate Server for updating NIS maps (managed
  by inetd)
• -------------------------------------------------
  --------------------------------------------------
  ------------------------------------

10
Setting Up an NIS Domain 1

• NIS must be initialized on the master server, on
  the slave servers, and on each client.
• It can be done in two steps.
• First, run ypinit on each server.
• Second, on every machine in the domain, set the
  domain name from one of the system startup files
  and configure /etc/passwd and /etc/group to
  import NIS data.

11
Setting Up an NIS Domain 2

• Configuring NIS servers
• ypinit is used to initialize both the master and
  slave servers for a domain.
• On the master, the following commands are used
• cd/var/yp / The NIS directory, wherever it is.
  /
• domainname foo / Name the new domain. /
• ypinit m / Initialize as master server. /
• /usr/etc/ypserv / Start the NIS server. /
• Once the master is up and running, each slave
  server should be primed by running ypinit with
  the s (slave) flag
• cd/var/yp
• ypinit s master / Argument is masters
  hostname. /
• /usr/etc/ypserv
• On each slave, you should set up crontab
  entries that pull fresh copies
• of all maps from the master. ypxfr
  map, where map is the mane such
• as passwd.byuid, will transfer the
  specified map from the master
• server. You must run the command
  once for each map

12
Setting Up an NIS Domain 3

• Configuring NIS Clients
• The second step is to inform each machine that it
  is a
• member of the new domain, and to configure it so
  that
• it pays attention to the network versions of
  /etc/passwd
• and /etc/group. The servers of a domain are
  generally
• clients as well. The /etc/passwd and /etc/group
  files
• on the master server are the files from which the
  NIS
• maps are built

13
Managing an NIS Server 1

• Managing an NIS server includes the
• following NIS server tasks
• Add an NIS slave server to a domain
• Adding a slave server to a domain enables the
  slave server to receive updated NIS maps from the
  master server and serve them to NIS clients in a
  domain.
• Remove an NIS slave server from a domain
• Removing a slave server from a domain means that
  the system will no longer receive updated NIS
  maps from the master server and serve them to NIS
  clients in a domain.
• Add a user to an NIS domain
• Adding a new user to an NIS domain includes the
  user in the passwd map and allows the user to
  participate in the NIS environment. A user has
  only one password on all systems that use NIS for
  their passwd map.

14
Managing an NIS Server 2

• Update an NIS map
• Updating an NIS map involves making changes to
  an NIS map's master file, updating the Makefile
  file (if the map is not listed), and building and
  distributing the new map.
• Add an NIS map to a domain
• Adding an NIS map to a domain allows the
  database information to be distributed throughout
  an NIS domain. You can create and distribute maps
  for any information you want to distribute.
• Remove an NIS map from a domain
• Removing an NIS map from a domain prevents the
  database information from being distributed
  throughout an NIS domain.

15
Managing an NIS Server 3

• Modify the /var/yp/Makefile file
• Adding an Entry
• Deleting an Entry
• Makefile Editing Guidelines
• Restrict access to NIS data
• By default, the ypserv and ypxfrd daemons provide
  NIS information to
• anyone with network access to an NIS server that
  makes a reqest. However,
• you can restrict NIS database access to only
  those hosts in subnets you
• specify

16
Managing an NIS client

• Managing an NIS client includes the
• following NIS client tasks
• Change in NIS password
• To change a user's password that is stored in
  the NIS passwd map, use the yppasswd command.
• Obtain map information
• Obtaining NIS map information enables you to see
  the following information
• Map names
• Map values
• Map keys
• Map master server

17
NIS

• NIS is a network name service similar to NIS but
  with more features. NIS is not an extension of
  NIS. It is a new software program
• NIS has some major advantages over NIS in
• Secure data access
• Hierarchical and decentralized network
  administration
• Very large namespace administration
• Access to resources across domains
• Incremental updates

18
Differences Between NIS and NIS
19
Reference

• UNIX System Administration Handbook, Second
  Editon, by Evi Nemeth et al, Prentice Hall PTR,
  Englewood Cliffs, New Jesey 07632
• http//www.media.mit.edu/captkirk/Dudoc/
• http//www.sun.com/smcc/
• http//www.microsoft.com/technet/win2000/win2ksrv/
  technote