Network Databases and the nsswitch.conf File
The network databases are files that provide information that is needed to configure
the network. The network databases follow:
hosts
ipnodes
netmasks
ethers database
bootparams
protocols
services
networks
As part of the configuration process, you edit the hosts database and the
netmasks database, if your network is subnetted. Two network databases, bootparams and ethers, are
used to configure systems as network clients. The remaining databases are used by
the operating system and seldom require editing.
Although nsswitch.conf file is not a network database, you need to configure this
file along with the relevant network databases. nsswitch.conf specifies which name service to use
for a particular system: local files, NIS, DNS, or LDAP.
How Name Services Affect Network Databases
The format of your network database depends on the type of name service
you select for your network. For example, the hosts database contains, at least
the host name and IPv4 address of the local system and any network
interfaces that are directly connected to the local system. However, the hosts database
could contain other IPv4 addresses and host names, depending on the type of
name service on your network.
The network databases are used as follows:
Networks that use local files for their name service rely on files in the /etc/inet and /etc directories.
NIS uses databases that are called NIS maps.
DNS uses records with host information.
Note - DNS boot and data files do not correspond directly to the network databases.
The following figure shows the forms of the hosts database that are used
by these name services.
Figure 10-2 Forms of the hosts Database Used by Name Services
The following table lists the network databases and their corresponding local files and
NIS maps.
Note - The ipnodes database is removed from Solaris releases after Solaris 10 11/06.
Table 10-1 Network Databases and Corresponding Name Service Files
Network
Database |
Local Files |
NIS Maps |
|---|
hosts |
/etc/inet/hosts |
hosts.byaddr hosts.byname |
ipnodes |
/etc/inet/ipnodes |
ipnodes.byaddr ipnodes.byname |
netmasks |
/etc/inet/netmasks |
netmasks.byaddr |
ethers |
/etc/ethers |
ethers.byname ethers.byaddr |
bootparams |
/etc/bootparams |
bootparams |
protocols |
/etc/inet/protocols |
protocols.byname protocols.bynumber |
services |
/etc/inet/services |
services.byname |
networks |
/etc/inet/networks |
networks.byaddr networks.byname |
This book discusses network databases as they are viewed by networks that use
local files for name services.
Refer to System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP) for information on network databases correspondences in NIS, DNS, and
LDAP.
nsswitch.conf File
The /etc/nsswitch.conf file defines the search order of the network databases. The Solaris
installation program creates a default /etc/nsswitch.conf file for the local system, based on the
name service you indicate during the installation process. If you selected the “None”
option, indicating local files for name service, the resulting nsswitch.conf file resembles the following
example.
Example 10-4
nsswitch.conf for Networks Using Files for Name Service
# /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 contains "switch.so" as a
# nametoaddr library for "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' backend for netgroup; the
# system will figure it out pretty quickly,
# and won't use netgroups at all.
netgroup: files
automount: files
aliases: files
services: files
sendmailvars: files
The nsswitch.conf(4) man page describes the file in detail. The basic syntax is
shown here:
database name-service-to-search
The database field can list one of many types of databases that are
searched by the operating system. For example, the field could indicate a database
that affects users, such as passwd or aliases, or a network database.
The parameter name-service-to-search can have the values files, nis, or nis+ for the
network databases. The hosts database can also have dns as a name service
to search. You can also list more than one name service, such as
nis+ and files.
In Example 10-4, the only search option that is indicated is files. Therefore, the local
system obtains security and automounting information, in addition to network database information, from
files that are located in its /etc and /etc/inet directories.
Changing nsswitch.conf
The /etc directory contains the nsswitch.conf file that is created by the
Solaris installation program. This directory also contains template files for the following name
services:
nsswitch.files
nsswitch.nis
nsswitch.nis+
If you want to change from one name service to another name
service, you can copy the appropriate template to nsswitch.conf. You can also selectively edit
the nsswitch.conf file, and change the default name service to search for individual
databases.
For example, on a network that runs NIS, you might have to
change the nsswitch.conf file on network clients. The search path for the
bootparams and ethers databases must list files as the first option, and
then nis. The following example shows the correct search paths.
Example 10-5
nsswitch.conf for a Client on a Network Running NIS
# /etc/nsswitch.conf:#
.
.
passwd: files nis
group: file 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: files [NOTFOUND=return] nis
netmasks: nis [NOTFOUND=return] files
bootparams: files [NOTFOUND=return] nis
publickey: nis
netgroup: nis
automount: files nis
aliases: files nis
# for efficient getservbyname() avoid nis
services: files nis
sendmailvars: files
For complete details on the name service switch, refer to System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).
bootparams Database
The bootparams database contains information that is used by systems that are configured
to boot in network client mode. You need to edit this database if
your network has network clients. See Configuring Network Clients for the procedures. The database is
built from information that is entered into the /etc/bootparams file.
The bootparams(4) man page contains the complete syntax for this database. Basic syntax
is shown here:
system-name file-key-server-name:pathname
For each network client system, the entry might contain the following information: the
name of the client, a list of keys, the names of servers, and
path names. The first item of each entry is the name of
the client system. All items but the first item are optional. An example
follows.
Example 10-6
bootparams Database
myclient root=myserver : /nfsroot/myclient \
swap=myserver : /nfsswap//myclient \
dump=myserver : /nfsdump/myclient
In this example, the term dump= tells client hosts not to look for
a dump file.
Wildcard Entry for bootparams
In most instances, use the wildcard entry when editing the bootparams database
to support clients. This entry follows:
* root=server:/path dump=:
The asterisk (*) wildcard indicates that this entry applies to all clients that
are not specifically named within the bootparams database.
ethers Database
The ethers database is built from information that is entered into the /etc/ethers
file. This database associates host names to their Media Access Control (MAC) addresses. You need to
create an ethers database only if you are running the RARP daemon. That
is, you need to create this database if you are configuring network clients.
RARP uses the file to map MAC addresses to IP addresses. If
you are running the RARP daemon in.rarpd, you need to set up the ethers
file and maintain this file on all hosts that are running the daemon
to reflect changes to the network.
The ethers(4) man page contains the complete syntax for this database. The basic
syntax is shown here:
MAC-address hostname #comment
- MAC-address
MAC address of the host
- hostname
Official name of the host
- #comment
Any note that you want to append to an entry in the file
The equipment manufacturer provides the MAC address. If a system does not display
the MAC address during the system booting process, see your hardware manuals for
assistance.
When adding entries to the ethers database, ensure that host names correspond to
the primary names in the hosts , not to the nicknames, as
follows.
Example 10-7 Entries in the
ethers Database
8:0:20:1:40:16 fayoum
8:0:20:1:40:15 nubian
8:0:20:1:40:7 sahara # This is a comment
8:0:20:1:40:14 tenere
Other Network Databases
The remaining network databases seldom need to be edited.
networks database
The networks database associates network names with network numbers, enabling some applications to
use and display names rather than numbers. The networks database is based on information
in the /etc/inet/networks file. This file contains the names of all networks to
which your network connects through routers.
The Solaris installation program configures the initial networks database. However, if you add
a new network to your existing network topology, you must update this database.
The networks(4) man page contains the complete syntax for /etc/inet/networks. The basic format is
shown here:
network-name network-number nickname(s) #comment
- network-name
Official name for the network
- network-number
Number assigned by the ISP or Internet Registry
- nickname
Any other name by which the network is known
- #comment
Any note that you want to append to an entry in the file
You must maintain the networks file. The netstat program uses the information
in this database to produce status tables.
A sample /etc/networks file follows.
Example 10-8
/etc/networks File
#ident "@(#)networks 1.4 92/07/14 SMI" /* SVr4.0 1.1 */
#
# The networks file associates Internet Protocol (IP) network
# numbers with network names. The format of this file is:
#
# network-name network-number nicnames . . .
# The loopback network is used only for intra-machine communication
loopback 127
#
# Internet networks
#
arpanet 10 arpa # Historical
#
# local networks
eng 192.168.9 #engineering
acc 192.168.5 #accounting
prog 192.168.2 #programming
protocols Database
The protocols database lists the TCP/IP protocols that are installed on your system
and their protocol numbers. The Solaris installation program automatically creates the database. This
file seldom requires any administration.
The protocols(4) man page describes the syntax of this database. An example of
the /etc/inet/protocols file follows.
Example 10-9
/etc/inet/protocols File
#
# Internet (IP) protocols
#
ip 0 IP # internet protocol, pseudo protocol number
icmp 1 ICMP # internet control message protocol
tcp 6 TCP # transmission control protocol
udp 17 UDP # user datagram protocol
services Database
The services database lists the names of TCP and UDP services and their
well-known port numbers. This database is used by programs that call network services.
The Solaris installation automatically creates the services database. Generally, this database does not require
any administration.
The services(4) man page contains complete syntax information. An excerpt from a typical
/etc/inet/services file follows.
Example 10-10
/etc/inet/services File
#
# Network services
#
echo 7/udp
echo 7/tcp
echo 7/sctp6
discard 9/udp sink null
discard 11/tcp
daytime 13/udp
daytime 13/tcp
netstat 15/tcp
ftp-data 20/tcp
ftp 21/tcp
telnet 23/tcp
time 37/tcp timeserver
time 37/udp timeserver
name 42/udp nameserver
whois 43/tcp nickname
