Part I About Naming and Directory Services

This part introduces the naming and directory services for the Solaris OS. It also describes the nsswitch.conf file that you use to coordinate the use of the different services.

Chapter 1 Naming and Directory Services (Overview)

This chapter provides an overview of naming and directory services used in Solaris. This chapter also briefly describes DNS, NIS, and LDAP naming services.

What Is a Naming Service?

Naming services store information in a central place, which enables users, machines, and applications to communicate across the network. This information can include the following.

• Machine (host) names and addresses

• User names

• Passwords

• Access permissions

• Group membership, printers, and so on

Without a central naming service, each machine would have to maintain its own copy of this information. Naming service information can be stored in files, maps, or database tables. If you centralize all data, administration becomes easier.

Naming services are fundamental to any computing network. Among other features, naming service provide functionality that does the following.

• Associates (binds) names with objects

• Resolves names to objects

• Removes bindings

• Lists names

• Renames

A network information service enables machines to be identified by common names instead of numerical addresses. This makes communication simpler because users do not have to remember and try to enter cumbersome numerical addresses like 192.168.0.0.

For example, take a network of three machines that are named, pine, elm, and oak. Before pine can send a message to either elm or oak, pine must know their numerical network addresses. For this reason, pine keeps a file, /etc/hosts or /etc/inet/ipnodes, that stores the network address of every machine in the network, including itself.

Likewise, in order for elm and oak to communicate with pine or with each other, the machines must keep similar files.

In addition to storing addresses, machines store security information, mail data, network services information and so on. As networks offer more services, the list stored of information grows. As a result, each machine might need to keep an entire set of files which are similar to /etc/hosts or /etc/inet/ipnodes.

A network information service stores network information on a server, which can be queried by any machine.

The machines are known as clients of the server. The following figure illustrates the client-server arrangement. Whenever information about the network changes, instead of updating each client's local file, an administrator updates only the information stored by the network information service. Doing so reduces errors, inconsistencies between clients, and the sheer size of the task.

This arrangement, of a server providing centralized services to clients across a network, is known as client-server computing.

Although the main purpose of a network information service is to centralize information, the network information service can also simplify network names. For example, assume your company has set up a network which is connected to the Internet. The Internet has assigned your network the network number 192.168.0.0 and the domain name doc.com. Your company has two divisions, Sales and Manufacturing (Manf), so its network is divided into a main net and one subnet for each division. Each net has its own address.

Each division could be identified by its network address, as shown above, but descriptive names made possible by naming services would be preferable.

Instead of addressing mail or other network communications to 198.168.0.0, mail could be addressed to doc. Instead of addressing mail to 192.168.2.0 or 192.168.3.0, mail could be addressed to sales.doc or manf.doc.

Names are also more flexible than physical addresses. Physical networks tend to remain stable, but company organization tends to change.

For example, assume that the doc.com network is supported by three servers, S1, S2, and S3. Assume that two of those servers, S1 and S3, support clients.

Clients C1, C2, and C3 would obtain their network information from server S1. Clients C4, C5, and C6 would obtain information from server S3. The resulting network is summarized in the following table. The table is a generalized representation of that network but does not resemble an actual network information map.

Now, assume that you create a third division, Testing, which borrowed some resources from the other two divisions, but did not create a third subnet. The physical network would then no longer parallel the corporate structure.

Traffic for the Test Division would not have its own subnet, but would instead be split between 192.168.2.0 and 192.168.3.0. However, with a network information service, the Test Division traffic could have its own dedicated network.

Thus, when an organization changes, its network information service can change its mapping as shown here.

Now, clients C1 and C2 would obtain their information from server S2. C3, C4 and C5 would obtain information from server S3.

Subsequent changes in your organization would be accommodated by changes to the network information structure without reorganizing the network structure.

Solaris Naming Services

The Solaris platform provides the following naming services.

• DNS, the Domain Name System (see Description of the DNS Naming Service)

• /etc files, the original UNIX® naming system (see Description of the /etc Files Naming Service)

• NIS, the Network Information Service (see Description of the NIS Naming Service)

• LDAP, the Lightweight Directory Access Protocol (see Part IV, LDAP Naming Services Setup and Administration LDAP Naming Services Setup and Administration)

Most modern networks use two or more of these services in combination. When more than one service is used, the services are coordinated by the nsswitch.conf file which is discussed in Chapter 2, The Name Service Switch (Overview).

Description of the DNS Naming Service

DNS is the naming service provided by the Internet for TCP/IP networks. DNS was developed so that machines on the network could be identified with common names instead of Internet addresses. DNS performs naming between hosts within your local administrative domain and across domain boundaries.

The collection of networked machines that use DNS are referred to as the DNS namespace. The DNS namespace can be divided into a hierarchy of domains. A DNS domain is a group of machines. Each domain is supported by two or more name servers, a principal server and one or more secondary servers. Each server implements DNS by running the in.named daemon. On the client's side, DNS is implemented through the “resolver.” The resolver's function is to resolve users' queries. The resolver queries a name server, which then returns either the requested information or a referral to another server.

Description of Multicast DNS and Service Discovery

Support for two extensions to the DNS protocol is now available. These two extensions are multicast DNS (mDNS) and DNS Service Discovery (DNS-SD). mDNS extends the Domain Name Service system to operate over link-local multicast. DNS-SD adds support for discovering network services over DNS.

Description of the /etc Files Naming Service

The original host-based UNIX naming system was developed for standalone UNIX machines and then adapted for network use. Many old UNIX operating systems and machines still use this system, but the system is not well suited for large complex networks.

Description of the NIS Naming Service

The Network Information Service (NIS) was developed independently of DNS. DNS makes communication simpler by using machine names instead of numerical IP addresses. NIS focuses on making network administration more manageable by providing centralized control over a variety of network information. NIS stores information about the network, machine names and addresses, users, and network services. This collection of network information is referred to as the NIS namespace.

NIS namespace information is stored in NIS maps. NIS maps were designed to replace UNIX /etc files, as well as other configuration files. NIS maps store much more than names and addresses. As a result, the NIS namespace has a large set of maps. See Working With NIS Maps for more information.

NIS uses a client-server arrangement which is similar to DNS. Replicated NIS servers provide services to NIS clients. The principal servers are called master servers, and for reliability, the servers have backup, or slave servers. Both master and slave servers use the NIS retrieval software and both store NIS maps. For more information on NIS Architecture and NIS Administration, see Chapter 5, Setting Up and Configuring NIS Service and Chapter 6, Administering NIS (Tasks).

Description of the LDAP Naming Services

The Solaris Operating System supports LDAP (Lightweight Directory Access Protocol) in conjunction with the Sun Java System Directory Server (formerly Sun ONE Directory Server), as well as other LDAP directory servers.

For information about LDAP naming services, see Chapter 8, Introduction to LDAP Naming Services (Overview/Reference) .

For information about transitioning from NIS to LDAP, see Chapter 15, Transitioning From NIS to LDAP (Overview/Tasks).

For information on single sign-on, as well as the setup and maintenance of Kerberos authentication services, see Part VI, Kerberos Service, in System Administration Guide: Security Services.

Naming Services: A Quick Comparison

Chapter 2 The Name Service Switch (Overview)

This chapter describes the name service switch. You use the name service switch to coordinate usage of different naming services.

About the Name Service Switch

The name service switch is a file which is named, nsswitch.conf. The name service switch controls how a client machine or application obtains network information. The name service switch is used by client applications that call any of the getXbyY() interfaces such as the following.

• gethostbyname()

• getpwuid()

• getpwnam()

• getaddrinfo()

Each machine has a switch file in its /etc directory. Each line of that file identifies a particular type of network information, such as host, password, and group, followed by one or more locations of that information.

A client can obtain naming information from one or more of the switch's sources. For example, an NIS client could obtain its hosts information from an NIS map and its password information from a local /etc file. In addition, the client could specify the conditions under which the switch must use each source. See Table 2–1.

The Solaris system automatically loads an nsswitch.conf file into every machine's /etc directory as part of the installation process. Four alternate (template) versions of the switch file are also loaded into /etc for LDAP, NIS, or files. See The nsswitch.conf Template Files.

These four files are alternate default switch files. Each file is designed for a different primary naming service: /etc files, NIS, or LDAP. When the Solaris software is first installed on a machine, the installer selects the machine's default naming service: NIS, local files, or LDAP. During installation, the corresponding template file is copied to nsswitch.conf. For example, for a machine client using LDAP, the installation process copies nsswitch.ldap to nsswitch.conf. Unless you have an unusual namespace, the default template file as copied to nsswitch.conf should be sufficient for normal operation.

No default file is provided for DNS, but you can edit any of these files to use DNS. For more information see DNS and Internet Access.

If you later change a machine's primary naming service, you copy the appropriate alternate switch file to nsswitch.conf. See The nsswitch.conf Template Files. You can also change the sources of particular types of network information used by the client by editing the appropriate lines of the /etc/nsswitch.conf file. The syntax is described below, and additional instructions are provided in How to Modify the Name Service Switch.

Format of the nsswitch.conf File

The nsswitch.conf file is essentially a list of 16 types of information and the sources that getXXbyYY() routines search for that information. The 16 types of information, not necessarily in this order, are the following.

• aliases

• bootparams

• ethers

• group

• hosts

• ipnodes

• netgroup

• netmasks

• networks

• passwd, which includes shadow information

• protocols

• publickey

• rpc

• services

• automount

• sendmailvars

The following table provides a description of the kind of sources that can be listed in the switch file for the information types above.

Search Criteria

Single Source. If an information type has only one source, such as nisplus a routine using the switch searches for the information in that source only. If the routine finds the information, the routine returns a success status message. If the routine does not find the information, the routine stops searching and returns a different status message. What the routine does with the status message varies from routine to routine.

Multiple Sources. If a table contains multiple sources for a given information type, the switch directs the routine to search in the first listed source. If the routine finds the information, the routine returns a success status message. If the routine does not find the information in the first source, the routine tries the next source. The routine searches all sources until the routine has found the information, or until the routine is halted by a return specification. If all of the listed sources are searched without finding the information, the routine stops searching and returns a non-success status message.

Switch Status Messages

If a routine finds the information, the routine returns a success status message. If the routine does not find the information, the routine returns one of three error status messages. Possible status messages are listed in the following table.

Switch Action Options

You can instruct the switch to respond to status messages with either of the two actions shown in the following table.

Default Search Criteria

The combination of nsswitch.conf file status message and action option determines what the routine does at each step. The combination of status and action make up the search criteria.

The switch's default search criteria are the same for every source. As described in terms of the status messages listed above, see the following.

• SUCCESS=return. Stop looking for the information. Proceed using the information that has been found.

• UNAVAIL=continue. Go to the next nsswitch.conf file source and continue searching. If this source is the last or only source, return with a NOTFOUND status.

• NOTFOUND=continue. Go to the next nsswitch.conf file source and continue searching. If this source is the last or only source, return with a NOTFOUND status.

• TRYAGAIN=continue. Go to the next nsswitch.conf file source and continue searching. If this source is the last or only source, return with a NOTFOUND status.

You can change default search criteria by explicitly specifying some other criteria by using the STATUS=action syntax shown above. For example, the default action for a NOTFOUND condition is to continue the search to the next source. For example, to specify for networks, the search should stop in a NOTFOUND condition, edit the networks line of the switch file. The line would read as follows.

networks: nis [NOTFOUND=return] files

The networks: nis [NOTFOUND=return] files line specifies a nondefault criterion for the NOTFOUND status. Nondefault criteria are delimited by square brackets.

In this example, the search routine behaves as follows:

• If the networks map is available, and contains the needed information, the routine returns with a SUCCESS status message.

• If the networks map is not available, the routine returns with an UNAVAIL status message. By default, the routine continues to search the appropriate /etc file.

• If the networks map is available and found, but the map does not contain the needed information, the routine returns with a NOTFOUND message. But, instead of continuing on to search the appropriate /etc file, which would be the default behavior, the routine stops searching.

• If the networks map is busy, the routine returns with an TRYAGAIN status message and by default continues on to search the appropriate /etc file.

Lookups in the nsswitch.conf file are done in the order in which items are listed. However, password updates are done in reverse order, unless otherwise specified by using the passwd -r repository command. See The Switch File and Password Information for more information.

What if the Syntax is Wrong?

Client library routines contain compiled-in default entries that are used if an entry in the nsswitch.conf file is either missing or syntactically incorrect. These entries are the same as the switch file's defaults.

The name service switch assumes that the table and source names are spelled correctly. If you misspell a table or source name, the switch uses default values.

Auto_home and Auto_master

The switch search criteria for the auto_home and auto_master tables and maps is combined into one category, which is called automount.

Timezone and the Switch File

The timezone table does not use the switch, so the table is not included in the switch file's list.

Comments in nsswitch.conf Files

Any nsswitch.conf file line beginning with a comment character (#) is interpreted as a comment line. A comment line is ignored by routines that search the file.

Characters preceding a comment mark are interpreted by routines that search the nsswitch.conf file. Characters to the right of the comment mark are interpreted as comments and ignored.

Keyserver and publickey Entry in the Switch File

You must restart the keyserver after you make a change to nsswitch.conf.

The keyserver reads the publickey entry in the name service switch configuration file only when the keyserver is started. If you change the switch configuration file, the keyserver does not register the changes until the keyserver is restarted.

The nsswitch.conf Template Files

Four switch template files are provided with the Solaris system to accommodate different naming services. Each file provides a different default set of information sources.

The four template files are the following.

• LDAP template file. The nsswitch.ldap configuration file specifies the LDAP directory as the primary source of information for the machine.

  ---

  Note –

  In order to use LDAP naming services, you must also properly configure all LDAP client machines, in addition to modifying the nsswitch.conf. See Chapter 12, Setting Up LDAP Clients (Tasks) for more information.

  ---

• NIS template file. The nsswitch.nis configuration file specifies NIS as the primary source for all information except passwd, group, automount, and aliases. For those four files, the primary source is local /etc files. The secondary source is an NIS map. The [NOTFOUND=return] search criterion instructs the switch to stop searching the NIS maps if the switch gets a “No such entry” message. The switch searches through local files only if the NIS server is unavailable.

  Because the search order for passwd and group is files nis, you don't need to place the + entry in the /etc/passwd and /etc/group files.

• Files template file. The nsswitch.files configuration file specifies local /etc files as the only source of information for the machine. There is no “files” source for netgroup, so the client does not use that entry in the switch file.

Copy the template file that most closely meets your requirements to the nsswitch.conf configuration file and then modify the file as needed.

For example, to use the LDAP template file, you would type the following command.

mymachine# cp /etc/nsswitch.ldap /etc/nsswitch.conf

The Default Switch Template Files

The following switch files are supplied with the Solaris product.

Example 2–1 NIS Switch File Template

#
# /etc/nsswitch.nis:
#
# An example file that could be copied over to /etc/nsswitch.conf;
# it uses NIS (YP) in conjunction with files.
#
# "hosts:" and "services:" in this file are used only if the
# /etc/netconfig file has a "-" for nametoaddr_libs of "inet"
# transports.
#
# the following two lines obviate the "+" entry in /etc/passwd
# and /etc/group.
passwd: files nis
group: files nis
# consult /etc "files" only if nis is down. 
hosts: nis [NOTFOUND=return] files
networks: nis [NOTFOUND=return] files
protocols: nis [NOTFOUND=return] files
rpc: nis [NOTFOUND=return] files
ethers: nis [NOTFOUND=return] files
netmasks: nis [NOTFOUND=return] files	
bootparams: nis [NOTFOUND=return] files
publickey: nis [NOTFOUND=return] files
netgroup: nis
automount: files nis
aliases: files nis
# for efficient getservbyname() avoid nis
services: files nis
sendmailvars: files

Example 2–2 Files Switch File Template

#
# /etc/nsswitch.files:
#
# An example file that could be copied over to /etc/nsswitch.conf;
# it does not use any naming service.
#
# "hosts:" and "services:" in this file are used only if the
# /etc/netconfig file has a "-" for nametoaddr_libs of "inet"
# transports.
passwd: files
group: files
hosts: files
networks: files
protocols: files
rpc: files
ethers: files
netmasks: files	
bootparams: files
publickey: files
# At present there isn't a 'files' back end for netgroup;
# the system will figure it out pretty quickly, and will notuse
# netgroups at all.
netgroup: files
automount: files
aliases: files
services: files
sendmailvars: files

Example 2–3 LDAP Switch File Template

#
# /etc/nsswitch.ldap:
#
# An example file that could be copied over to /etc/nsswitch.conf; it
# uses LDAP in conjunction with files.
#
# "hosts:" and "services:" in this file are used only if the
# /etc/netconfig file has a "-" for nametoaddr_libs of "inet" transports.

# the following two lines obviate the "+" entry in /etc/passwd 
and /etc/group.
passwd:     files ldap
group:      files ldap

hosts:      ldap [NOTFOUND=return] files

networks:   ldap [NOTFOUND=return] files
protocols:  ldap [NOTFOUND=return] files
rpc:        ldap [NOTFOUND=return] files
ethers:     ldap [NOTFOUND=return] files
netmasks:   ldap [NOTFOUND=return] files
bootparams: ldap [NOTFOUND=return] files
publickey:  ldap [NOTFOUND=return] files

netgroup:   ldap

automount:  files ldap
aliases:    files ldap

# for efficient getservbyname() avoid ldap
services:   files ldap
sendmailvars:   files

The nsswitch.conf File

The default nsswitch.conf file that is installed with the Solaris software is determined by which naming service you select during the installation process. Each line identifies a particular type of network information, such as host, password, and group, along with the information source, such as NIS maps, the DNS hosts table, or local /etc. When you chose a naming service, the switch template file for that service is copied to create the new nsswitch.conf file. For example, if you choose NIS, the nsswitch.nis file is copied to create a new nsswitch.conf file.

An nsswitch.conf file is automatically loaded into every machine's /etc directory by the Solaris 9 release software, along with the following alternate (template) versions.

• /etc/nsswitch.nisplus

• /etc/nsswitch.nis

• /etc/nsswitch.files

• /etc/nsswitch.ldap

These alternate template files contain the default switch configurations used by the NIS services, local files, and LDAP. No default file is provided for DNS, but you can edit any of these files to use DNS. When the Solaris software is first installed on a machine, the installer selects the machine's default naming service. During installation, the corresponding template file is copied to /etc/nsswitch.conf. For example, for a machine client using NIS, the installation process copies nsswitch.nis to nsswitch.conf.

If your network is connected to the Internet and users must access Internet hosts using DNS, you must enable DNS forwarding.

Unless you have an unusual namespace, the default template file as copied to nsswitch.conf should be sufficient for normal operation.

Selecting a Different Configuration File

When you change a machine's naming service, you need to modify that machine's switch file accordingly. For example, if you change a machine's naming service from files to NIS, you need to install a switch file appropriate for NIS. You change switch files by copying the appropriate template file to nsswitch.conf.

Before proceeding to change switch files, make sure the sources listed in the file are properly set up. In other words, if you are going to select the NIS version, the client must eventually have access to NIS service. If you select the local files version, those files must be properly set up on the client.

How to Modify the Name Service Switch

To change to a switch file, follow these steps.

In order to use LDAP naming services, you must also properly configure all LDAP client machines, in addition to modifying the nsswitch.conf. See Chapter 12, Setting Up LDAP Clients (Tasks) for more information.

1. Become superuser or assume an equivalent role.

   Roles contain authorizations and privileged commands. For more information about roles, see Chapter 9, Using Role-Based Access Control (Tasks), in System Administration Guide: Security Services.

2. Copy the appropriate alternate file for the machine's naming service over the nsswitch.conf file.

   NIS Version

   client1# cd /etc client1# cp nsswitch.nis nsswitch.conf

   Local /etc Files Version

   client1# cd /etc client1# cp nsswitch.files nsswitch.conf

3. Reboot the machine.

   The nscd daemon caches switch information. See the nscd(1M) man page for information.

   Some library routines do not periodically check the nsswitch.conf file to see whether the file has been changed. You must reboot the machine to make sure that the daemon and those routines have the latest information in the file.

DNS and Internet Access

The nsswitch.conf file also controls DNS forwarding for clients as described in the following subsections. DNS forwarding grants Internet access to clients.

IPv6 and Solaris Naming Services

NIS and LDAP support storing IPv6 data, as well as using IPv6 transports for protocol traffic. Beginning with BIND version 8.3.3, DNS on the Solaris OS supports the use of IPv6 transports on the client side. As of BIND version 8.4.2, DNS provides a complete client-server solution over IPv6 networks on Solaris.

The nsswitch.conf file controls search criteria for IPv6 addresses. IPv6 increases the IP address size from 32 bits to 128 bits to support more levels of addressing hierarchy. A larger address size provides a greater number of addressable nodes. For more information about IPv6, its configuration and implementation, see System Administration Guide: IP Services.

Use the new ipnodes source for IPv6 addresses. The /etc/inet/ipnodes file stores both IPv4 and IPv6 addresses. The /etc/inet/ipnodes file uses the same format convention as the /etc/hosts file.

IPv6 aware naming services use the new ipnodes source for its search forwarding. For instance, if LDAP is aware of IPv6 addresses, specify the following.

ipnodes: ldap [NOTFOUND=return] files

Potential delay issues:

• ipnodes defaults to files. During the transition from IPv4 to IPv6, where all naming services are not aware of IPv6 addresses, accept the files default. Otherwise, unnecessary delays, such as boot timing delays, might result during the resolution of addresses.

• An application searches all ipnodes databases for IPv4 addresses before searching for IPv4 addresses in the hosts databases. Before specifying ipnodes, consider the inherent delay of searching both databases for IPv4 addresses.

Ensuring Compatibility With +/- Syntax

If +/- is used in /etc/passwd, /etc/shadow, and /etc/group files, you need to modify the nsswitch.conf file to insure compatibility.

NIS. To provide the same syntax as in the Solaris 4.x release, change the passwd and groups sources to compat.

passwd: compat
group: compat

Specifies the /etc files and NIS maps as indicated by the +/- entries in the files.

The Switch File and Password Information

It is possible to include and access password information in multiple repositories, such as files and nisplus. You can use the nsswitch.conf file to establish the lookup order for that information.

files must be the first source in the nsswitch.conf file for passwd information.

In an NIS environment, the passwd line of the nsswitch.conf file should list the repositories in the following order.

passwd: files nis

Listing files first allows root to log in, under most circumstances, even when the system encounters some network or naming services issues.

Maintaining multiple repositories for the same user is not recommended. By maintaining centralized password management in a single repository for each user, you reduce the possibilities of confusion and error. If you choose to maintain multiple repositories per user, update password information by using the passwd -r command.

passwd -r repository

If no repository is specified with the -r option, passwd updates the repositories listed in nsswitch.conf in reverse order.