7 Booting a RIS Client

This chapter describes the network files and daemons that the RIS utility uses and the sequence of events that occur when a client broadcasts a bootp request. If you use RIS to install the operating system on a client, the client must boot across the network.

Note
The client must be registered on the RIS server before you can install the operating system.

7.1 Remote Boot Files and Daemons

Table 7-1 describes the files and daemons used by RIS servers to boot a remote client.

Table 7-1: Remote Boot Files and Daemons

Name	Description
`/etc/bootptab`	Contains information needed to boot remote clients
`/sbin/init.d/dhcp`	Script used to start `joind`
`/etc/inetd.conf`	Contains start-up information for various internet daemons
`/usr/sbin/joind`	`bootp` server daemon (handles `bootp` requests)
`/usr/sbin/tftpd`	`tftpd` server daemon
`/usr/sbin/inetd`	Internet server daemon
`/sbin/init.d/dhcp`	Script used to start `joind`

7.1.1 Internet Daemon and its Configuration File

On a Digital UNIX system, network boots occur using the bootp protocol. This protocol is serviced by one of two daemons: bootpd and joind. For Digital UNIX Version 4.0, Digital recommends the use of the joind daemon. The bootpd daemon is started using the internet daemon, the joind daemon is not. The inetd daemon starts networking-related daemons on a Digital UNIX system. Some of these daemons, such as tftpd, are related to RIS; others, such as fingerd, are not. On request, the inetd daemon starts any of the daemons listed in its configuration file, /etc/inetd.conf.

7.1.2 The bootp Daemon (bootpd/joind)

The bootp daemon handles remote boot requests. It handles any bootp requests received by the RIS server. As it starts up, the bootp daemon reads its /etc/bootptab file to determine the systems from which it will recognize remote boot requests. Whenever the /etc/bootptab file is modified, the bootp daemon rereads it.

Section 7.1.3 describes the content and format of the /etc/bootptab file. See joind(8) or bootpd(8) for more information.

7.1.3 The /etc/bootptab File

The /etc/bootptab file is a text file that contains information that a server needs to boot a remote client. The ris utility adds and removes entries from this file during client management. Other applications may also place entries in the /etc/bootptab file.

The general format for entries in the bootptab file is as follows:

tag : tg= value... : tg= value... : tg= value... ...

Example 7-1 describes the entries in the /etc/bootptab file for RIS clients.

For additional information about the contents of the bootptab file, see the joind(8) reference page.

Example 7-1: Sample /etc/bootptab File

.ris.dec:hn:vm=rfc1048                                      [1]
.ris0.alpha:tc=.ris.dec:bf=/var/adm/ris/ris0.alpha/vmunix:  [2]
spike:tc=.ris0.alpha:ht=ethernet:gw=16.69.224.222: \
  ha=08002b309668:ip=16.30.0.143:                           [3]
.ris93.alpha:tc=.ris.dec:bf=/ris/ris93.a/vmunix: \
  rp="ds9:/ris/ris93.a/product_001":                        [4]

The .ris.dec entry defines characteristics common to all clients. The fields specify the following:
- hn: Tells the boot server to send the name of the client system to the client when it makes a boot request.
- vm: Vendor-specific information
[Return to example]
The .risn.arch entry, in this example .ris0.alpha, defines characteristics common to all clients using this RIS area. The fields specify the following:
- tc: Table continuation The tc field lets you follow pointers back to common entries. For example, the tc entry for .ris0.alpha in Example 7-1 points to the .ris.dec entry. The .ris.dec entry contains the common hardware type (ht) and vendor specific (vm) information. The .ris0.alpha entry, itself, contains common information about the boot file location.
- bf: Name of the boot file
[Return to example]
The hostname entry, in this example spike, defines characteristics for a specific client. The fields specify the following:
- tc: Table continuation The following describes the entry for the host spike: its tc entry points to ris0.alpha, which contains its boot file information. The ris0.alpha, entry in turn points back to ris.dec, which contains relevant hardware type and vendor specific information.
  If you added another host entry to the /etc/bootptab file, it would look similar to the following:
```
lee:tc=ris0.alpha:ht=ethernet:ha=08002b390668: \
  ip=16.140.64.249:
```
- ht: The client's hardware type is either ethernet, fddi, or ieee802 (for Token Ring)
- ha: Client's network hardware address
- ip: Client's IP address
[Return to example]
The .ris93.alpha entry defines characteristics for a Digital UNIX Version 4.0 and later RIS area. The fields specify the following:
- tc: Table continuation The tc field lets you follow pointers back to common entries. For example, the tc entry for .ris93.alpha in Example 7-1 points to the .ris.dec entry. The .ris.dec entry contains the common hardware type (ht) and vendor specific (vm) information. The .ris93.alpha entry contains common information about the boot file location.
- bf: Name of the boot file
- rp: The rp parameter points the client to the point where it will mount its root on the server.
[Return to example]

7.1.4 The tftpd Daemon

The tftpd daemon handles the transfer of the boot file during a remote boot. This daemon starts when there is a file to be transferred. See the tftpd(8) reference page for more information.

7.2 Remote Boot Flow

Digital UNIX client systems use the bootp protocol to perform the remote bootstrap operation from a Digital UNIX RIS server. The command used to initiate a remote boot is processor specific. For additional information, see the Installation Guide. However, once the remote boot operation has started, the underlying process is the same for all Digital UNIX systems that support network booting:

The processor-specific remote boot command is issued at the client console prompt.
The client processor firmware sends a bootp packet over the Ethernet. This packet contains the hardware Ethernet address of the client.
The bootp server daemon compares the Ethernet hardware address in the packet with the client registration information stored in its /etc/bootptab file to determine if the client requesting the remote boot is registered to the server.
If the address matches one in its /etc/bootptab file, the bootp daemon sends to the client a packet of information that includes the server's Internet address, client's Internet address, and the name of the file to be loaded from the server. This information was placed in the bootptab file by the ris utility when the client was registered on the server.
Internet addresses are used to set up a network that is used to download to the client processor the file specified in the bootptab file. For Digital UNIX RIS clients, this file is /var/adm/risn.alpha/vmunix, where risn.alpha corresponds to the RIS area to which the client is registered. This file is the Digital UNIX standalone operating system used to start the installation.
The client system requests the file from the server system.
The client and server system use the tftp protocol to transfer vmunix to the client.
Once vmunix is loaded, the client system begins to execute vmunix and the Digital UNIX standalone system messages are displayed on the client console terminal.

After the operating system is installed, the client is a self-supporting system. Follow normal procedures to boot the system from its own local disk.