Using NIS to maintain host information

Advantage of using NIS

Like DNS, NIS enables you to centrally maintain host information. NIS provides two methods for storage system host-name resolution:

Using a makefile master on the NIS server, which creates a /etc/hosts file and copies it to your storage system's default volume for local host name lookup
This method is described in Creating /etc/hosts from the NIS master.
Using a hosts map, maintained as a database on the NIS server, which your storage system queries in a host lookup request across the network
This method is described in this section.

NIS also enables you to maintain user information. For more information, see the Data ONTAP System Administration Guide.

Using NIS slave for name resolution

Host-name resolution using a hosts map can have a performance impact, because each query for the hosts map is sent across the network to the NIS server. To improve performance, you can enable an NIS slave on your storage system.

The NIS slave establishes a contact with an NIS master server and does the following two tasks:

Downloads the maps from the NIS master server
Once the maps have been downloaded, they are stored in the /etc/yp/nis_domain_name/ directory. All NIS requests from your storage system are then serviced by the NIS slave using these maps. The NIS slave checks the NIS master every 45 minutes for any changes to the maps. If there are changes, they are downloaded.
Listens for updates from the NIS master
When the maps on the NIS master are changed, the NIS master administrator can choose to notify all slaves. Therefore, in addition to periodically checking for updates from the NIS master, the NIS slave also listens for updates from master.

Note
The NIS slave does not respond to remote NIS client requests and thus cannot be used by other NIS clients for name lookups.

Selection of an NIS master

When the NIS slave is enabled on your storage system, the NIS servers listed with the nis.servers option are contacted to determine the master NIS server. The NIS master can be different from the servers listed with the nis.servers option. If that is the case, the servers listed with the nis.servers option inform the slave about the master server.

Note
Either the NIS server must have an entry in the hosts map for the master or the /etc/hosts file on your storage system must be able to resolve the IP address of the master. Otherwise, the NIS slave on the storage system cannot contact the master.

Guidelines for using the NIS slave

Keep the following guidelines in mind when using the NIS slave on your storage system:

The root volume of your storage system must have sufficient space to download maps for the NIS slave. Typically, the space required in the root volume is same as the size of the maps on the NIS server.
If the root volume does not have enough space to download maps, the following occurs:
- An error message is displayed informing you that the space on the disk is not sufficient to download or update the maps from the NIS master.
- If the maps cannot be downloaded, the NIS slave is disabled. Your storage system switches to using hosts map on the NIS server for name resolution.
- If the maps cannot be updated, your storage system continues to use the old maps.
If the NIS master server was started with the -d option or if the hosts.byname and hosts.byaddr maps are generated with the -b option, your storage system must have DNS enabled, DNS servers must be configured, and the hosts entry in the /etc/nswitch.conf file must contain DNS as an option to use for host name lookup.
If you have your NIS server configured to do host name lookups using DNS or if you use DNS to resolve names that cannot be first resolved using the hosts.by* maps, using the NIS slave causes those lookups to fail, because when the NIS slave is used, all lookups are performed locally using the downloaded maps. However, if you configure DNS on your storage system as described previously, the lookups succeed.
You can use the NIS slave for the following:
- Vif and VLAN interfaces
- vFiler units
- Storage system clusters
  Note
  Ensure that the nis.servers options value is the same on both cluster nodes and that the /etc/hosts file on both cluster nodes can resolve the name of the NIS master server.

About configuring NIS for host lookups

You can configure your storage system to use one or more NIS servers either during the setup procedure or later using the Data ONTAP command line or FilerView.

If you configure NIS later, you need to do all of the following:

Specify the NIS server to which your storage system should bind
Specify the NIS domain name of your storage system
Enable NIS on your storage system

You cannot configure the NIS slave during the setup procedure. To configure the NIS slave after the setup procedure is complete, you need to enable NIS slave by setting the option nis.slave.enable to On. For more information about enabling NIS slave, see Enabling an NIS slave on your storage system.

Data ONTAP interfaces to configure NIS

You can enable NIS and set NIS configuration values in either of these ways:

Using FilerView
See Configuring NIS with FilerView.

You cannot use FilerView to configure the NIS slave.
At the command line
See the appropriate instructions:

If you want to use primarily NIS for host-name resolution, specify it ahead of other methods in the hosts map in the /etc/nsswitch.conf file. For information about editing the /etc/nsswitch.conf file, see Changing the host name search order.

Correct host-name resolution depends on the correct configuration of the NIS server. If you experience problems with host-name resolution or data availability, check the NIS server in addition to local networking.

For more information about your storage system's NIS client, see the na_nis(8) man page.

Configuring NIS with FilerView

To set or modify NIS configuration values with FilerView, complete the following steps.

Step	Action
1	In FilerView, click Network in the list on the left.
2	In the list under Network, click Manage DNS and NIS Name Service.
3	If you want to....	Then...
	Enable or disable NIS	Select Yes or No in the NIS Enabled field.
	Set or modify the NIS domain name	Enter a name in the NIS Domain Name field. Examples of configuration values are listed in Specifying the NIS domain name.
	Specify or modify NIS servers	Enter one or more IP addresses in the NIS Servers fields. Examples of configuration values are listed in Specifying NIS servers to bind to.

Enabling or disabling NIS using the command-line interface

To enable or disable NIS on your storage system, complete the following step.

Step	Action
1	Enter the following command: options nis.enable {on\|off} Use `On` to enable and `Off` to disable NIS.

Specifying the NIS domain name

To specify the NIS domain name, complete the following step.

Step	Action
1	Enter the following command: options nis.domainname domain domain is the NIS domain name to which your storage system belongs; for example, typical NIS domain names might be sales or marketing. The NIS domain name is usually not the same as the DNS domain name.

Specifying NIS servers to bind to

You can specify an ordered list of NIS servers to which you want your storage system to bind. The list should begin with the closest NIS server (closest in network terms) and end with the furthest one.

To specify an ordered list of NIS servers you want your storage system to bind to, complete the following step.

Note
You can specify NIS servers by IP address or host name. If host names are used, make sure each host name, along with its IP address, is listed in the /etc/hosts file of your storage system. Otherwise, the binding with host name will fail.

Step	Action
1	Enter the following command to specify the NIS servers and their order: options nis.servers ip_address, server_name, * The asterisk () specifies that broadcast is used to bind to NIS servers if the servers in the list are not responding. This is the default. If you do not specify broadcasting (that is, if you do not add the asterisk), and none of the listed servers is responding, NIS services are disrupted until one of the preferred servers responds. You can specify only IPv4 addresses or server names that resolve to IPv4 addresses using the /etc/hosts file on your storage system. Attention* Using the NIS broadcast feature can incur security risks.

Step

Action

Enter the following command to specify the NIS servers and their order:

options nis.servers ip_address, server_name, *

The asterisk (*) specifies that broadcast is used to bind to NIS servers if the servers in the list are not responding. This is the default. If you do not specify broadcasting (that is, if you do not add the asterisk), and none of the listed servers is responding, NIS services are disrupted until one of the preferred servers responds.

You can specify only IPv4 addresses or server names that resolve to IPv4 addresses using the /etc/hosts file on your storage system.

Attention
Using the NIS broadcast feature can incur security risks.

Example of specifying NIS servers to bind to

The following lists two servers and uses the broadcast default:

options nis.servers 172.15.16.1,nisserver-1,*

Your storage system first tries to bind to 172.15.16.1. If the binding fails, the storage system tries to bind to nisserver-1. If this binding also fails, the storage system binds to any server that responds to the broadcast. While bound to the NIS server that responded to the broadcast, the storage system continues to poll the preferred servers. As soon as one of the preferred servers is found, the storage system binds to the preferred server.

Enabling an NIS slave on your storage system

To enable an NIS slave on your storage system, complete the following step.

Step	Action
1	Enter the following command: options nis.slave.enable {on\|off} Use `on` to enable the NIS slave and `off` to disable it. Note If the NIS slave is disabled, your storage system reverts back to the original configuration, in which it contacts an NIS server to resolve host names.

Displaying NIS information

You can display the following types of NIS information:

NIS domain name
Last time the local group cache was updated
The following information about each NIS server that was polled by your storage system:
- IP address of the NIS server
- Type of NIS server
- State of the NIS server
- Whether your storage system is bound to the NIS server
- Time of polling
Whether an NIS slave is enabled or not
NIS master server
Last time the NIS map was checked by the NIS slave

To display NIS information, complete the following step.

Step	Action
1	Enter the following command: nis info

For more information about the nis info command and resulting display, see the na_nis(1) man page.

NIS administrative commands

Data ONTAP supports the standard NIS administrative commands listed in the following table. For more information, see each command's man page.

Command	Function
`ypcat`	Prints an entire NIS map
`ypgroup`	Displays the NIS group cache entries
`ypmatch`	Looks up specific entries in an NIS map
`ypwhich`	Returns the name of the current NIS server