What Are Servers and Clients

Systems on the network can usually be described as one of the following:

• Server - A system that provides services to other systems in its network. There are file servers, boot servers, database servers, license servers, print servers, installation servers, and even servers for particular applications. This chapter uses the term server to mean a system that provides file systems and installation software for other systems on the network.
• Client - A system that uses remote services from a server. Some clients have limited disk storage capacity, or perhaps none at all, and they have to rely on remote file systems from a server to function. Diskless and dataless clients are examples of this type of client.

  Other clients may use remote services (such as installation software) from a server, but they don't rely on a server to function. A standalone system, which has its own hard disk containing the root (/), /usr, and /home file systems and swap space, is a good example of this type of client.

What Does Support Mean

Providing support for a system means providing software and services to help another system function. Support can include:

• Making a system known to the network (i.e., host name and ethernet address information)
• Providing installation services to remotely boot and install a system
• Providing operating system (OS) services to a system with limited or no disk space

Overview of System Types

System types are basically defined by how they access the root (/) and /usr file systems, including the swap area. For example, standalone and server systems mount these file systems from a local disk, while diskless and dataless clients mount the file systems remotely, relying on servers to provide these services. Table 3-1 lists these and other differences for each system type.

Table 3-1

System Type	Local File Systems	Local Swap?	Remote File Systems	Network Use	Relative Performance
Server	root (/) /usr /home /opt /export/home /export/root	Yes	- none -	medium	high
Standalone System	root (/) /usr /export/home	Yes	- none -	low	high
Dataless Client	root (/)	Yes	/usr /home	medium	medium
Diskless Client	- none -	No	root (/) swap /usr /home	high	low
(TM) AutoClient System	cached root (/) cached /usr	Yes	/var /home	low	high

Servers

A server system has the following file systems:

• The root (/) and /usr file systems, plus swap space
• The /export, /export/swap, and /export/home file systems, which support client systems and provide home directories for users.
• The /opt directory or file system for storing application software.

Servers can also contain the following software to support other systems:

• Operating system (OS) services for diskless and dataless clients that want to run a different release or are a different platform than the server.
• Solaris CD image and boot software for networked systems to perform remote installations.
• JumpStart^(TM) directory for networked systems to perform custom JumpStart installations.

Standalone Systems

A networked standalone system can share information with other systems in the network, but it could continue to function if detached from the network.

A standalone system can function autonomously because it has its own hard disk containing the root (/), /usr, and /home file systems and swap space. The standalone system thus has local access to operating system software, executables, virtual memory space, and user-created files.

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Note - A standalone system requires sufficient disk space to hold the four necessary file systems.

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A non-networked standalone system is a standalone system with all the characteristics listed above except that is not connected to a network.

Diskless Clients

A diskless client has no disk and depends on a server for all its software and storage area. A diskless client remotely mounts its root (/), /usr, and /home file systems from a server.

A diskless client generates significant network traffic due to its continual need to procure operating system software and virtual memory space from across the network. A diskless client cannot operate if it is detached from the network or if its server malfunctions.

Dataless Clients

A dataless client has local storage for its root (/) file system and swap space. The dataless client cannot function if detached from the network, because its executables (/usr) and user files (/home) are located across the network on the disk of a server.

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Note - SunSoft plans to remove support for dataless clients after Solaris 2.5. You can add this system type now using Host Manager, but in future releases of the Solaris operating environment you will need to choose a different type.

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A dataless client places far less demand on the server and the network than a diskless client does. Because dataless clients require less network access, a server can accommodate many more dataless clients than it can diskless clients.

Dataless clients are less expensive to manage than standalone systems. Also, the user files of all the dataless clients are stored centrally (on a server) and can be backed up and administered centrally.

However, if local security is an issue at your site, you need to weigh these conveniences against the relative lack of security of centralized files.

AutoClient Systems

An AutoClient system is nearly identical to a diskless client in terms of installation and administration. It has the following characteristics:

• Requires a 100-Mbyte local disk for swapping and for caching its individual root (/) file system and the /usr file system from a server

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Note - The /var directory should not be cached on the AutoClient system. The /var directory is volatile, and therefore is not suitable for caching.

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• Relies on a server to access other file systems and software applications
• Contains no permanent data, making it a field replaceable unit (FRU)

AutoClient systems use the Solstice AutoClient technology and must be added and maintained by using the AutoClient Manager.

Guidelines for Choosing System Types

Determining which system types are appropriate for your environment can be done by comparing each type based on the following characteristics:

• Centralized Administration

  · Can the system be treated as a field replaceable unit (FRU)? This means that a broken system can be quickly replaced with a new system without any lengthy backup/restore operations and no loss of system data.

  · Does the system need to be backed up? Large costs in terms of time and resources can be associated with backing up a large number of desktop systems.

  · Can the system's data be modified from a central server?

  · Can the system be installed from a centralized server, quickly and easily without handing the client system's hardware?

• Performance

  · Does this configuration perform well in desktop usage?

  · Does the addition of systems on a network affect the performance of other systems already on the network?

• Disk Usage

  · How much disk space is required to effectively deploy this configuration?

Table 3-2 describes how each system type scores in terms of each of these categories. A ranking of 1 is most efficient; a ranking of 4 is least efficient.

Table 3-2

System Type	Centralized Administration	Performance		Disk Usage
Standalone System	4		1		4
Diskless Client	1		4		1
Dataless Client	3		3		2
AutoClient System	1		2		2

Tools for Managing Server and Client Support

In previous Solaris releases, you may have used Administration Tool to manage server and client support. In the Solaris 2.5 release, you must use the Solstice Host Manager tool, which offers ease of use and provides support for the following name services:

• NIS+ tables
• NIS maps
• Local /etc files

What You Can Do With Host Manager

Host Manager is a graphical user interface that enables you to add and maintain server and client support on a network. With a name service like NIS+, you can manage system information in a centralized manner so that important system information, such as host names, does not have to be duplicated on every system in the network.

Host Manager enables you to:

• Add and modify support
• Update system types
• Convert system types
• Add OS services
• Set up remote installation services

Add and Maintain Support

Host Manager enables you to add and modify support for the following Solaris system types:

• Diskless
• Dataless
• Standalone
• OS Server

Table 3-3 describes the server-client configurations that are supported by the Solstice AdminSuite 2.1 release of Host Manager.

Table 3-3

			Client
SunOS 4.x		Solaris 2.3		Solaris 2.4		Solaris 2.5
SPARC	x86		SPARC	x86	SPARC	x86	SPARC
Yes	-		-	Yes	Yes	Yes	Yes
Yes	-		Yes	Yes	Yes	Yes	Yes
Yes	-		Yes	Yes	Yes	Yes	Yes
Yes	-		Yes	Yes	Yes	Yes	Yes
Yes	-		Yes	Yes	Yes	Yes	Yes
Yes	-		Yes	Yes	Yes	Yes	Yes

	Solaris 2.3	x86
		SPARC
Server	Solaris 2.4	x86
		SPARC
	Solaris 2.5	x86
		SPARC

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Note - SunOS 4.x can only run on SPARC systems that are Sun4c and Sun4m platform groups.

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Update System Types

Host Manager cannot recognize all previously added system types until you use the Update System Types option from the File menu. This option will probe client systems and identify their system types. Host Manager will mark systems as generic if they are not running the Solaris software or if they use local or loghost entries.

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Note - Previously added systems running Solaris 2.5 must also have the Solstice AdminSuite software installed for Host Manager to update their system type.

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The system type information is stored in the bootparams file in the local /etc files or a name service database. Host Manager will either modify an existing bootparams entry or add a new one such as the following for a Solaris standalone system named mars:

mars    boottype=:st

Convert System Types

Host Manager enables you to convert one system type to another. Currently, you can only convert:

• A generic system to a standalone system
• A standalone system to an OS server

You can add Solaris 2.x OS services during the standalone system to OS server conversion.

Add OS Services

A Solaris OS server is a server that provides operating system (OS) services to support diskless or dataless clients. By using Host Manager, you can add support for an OS server or convert a standalone system to an OS server.

By default, an OS server can support clients that are the same platform group and require the same Solaris release as the OS server. To support clients of a different platform group or clients that require a different Solaris release than the OS server, you must add the particular OS service to the OS server. You must have the appropriate Solaris CD image to add OS services.

For example, if you have a OS server running Solaris 2.5 and you want it to support diskless clients running Solaris 2.4, you must add Solaris 2.4 OS services to the OS server. You would also have to add services to a SPARC OS server if you want it to support x86 diskless clients running Solaris 2.4. In this example, both the server and client are running the same Solaris release, but they are different platform groups.

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Note - Although Host Manager enables you to add support for diskless and dataless clients running the Sun4.x release, you cannot add SunOS 4.x OS services using Host Manager. You must use the discover4x and install4x commands to add OS services to an OS server, and then use Host Manager to add support for the SunOS 4.x client.

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Set Up Remote Installation Services

Host Manager enables you to set up systems to provide Solaris 2.x installation services for other systems on the network. You can set up the following types of installation services on a system:

• An install server - A system on the network that provides a Solaris CD image (either from a CD-ROM drive or the copy on the hard disk) for other systems to install from.
• A boot server - A system that provides boot information to other systems on the network.
• A profile server - A system that contains Jumpstart files for systems to perform a custom JumpStart installation.

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Note - A boot server and install server are typically the same system. However, if the system to be installed is on a different subnet than the install server, a boot server is required on that subnet.

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What You Can't Do With Host Manager

Table 3-4 shows the limitations of Host Manager and their suggested workarounds.

Table 3-4

Limitation	Workaround
Host Manager cannot automatically recognize all previously added system types.	Use the Update System Type option from the File menu. This option will probe systems on the network and identify their system types.

Table 3-4 (Continued)

Limitation	Workaround
Host Manager cannot add or maintain AutoClient systems.	Use the Solstice AutoClient Manager to create and maintain AutoClient systems. AutoClient Manager is provided with the Solstice AutoClient product.
Host Manager can't add SunOS 4.x services to an OS server.	Mount a SunOS 4.x CD image and add OS services by using the discover4x and install4x commands.
Host Manager can't provide remote installation services for SunOS 4.x systems.	Install SunOS 4.x systems from the local CD-ROM drive.
Host Manager does not enable you to add multiple host entries for a system with the same Ethernet address (needed for servers with multiple Ethernet interfaces, also known as multi-home hosts).	Use command-line equivalents to enter the host information into the name service.