Novell Documentation: Novell Linux Point of Service

2.2 Branch Server

The Branch Server provides the network boot and system management infrastructure for the Point of Service terminals. It can also serve as a generic system platform for in-store applications such as database systems and back-ends for Point of Service applications.

In a Novell Linux Point of Service system, the Branch Server provides the following services:

Runs DNS services for the local network.
Runs DHCP so it can control the network boot process.
Provides a multicast boot infrastructure for Point of Service terminals.
Transfers client images from the Administration Server to the Point of Service terminals.
The Branch Server uses a software distribution mechanism based on RSYNC to pull new client images from the Administration Server. It then uses TFTP to download client images and configuration files to the Point of Service terminals.
Manages diskless and disk-based Point of Service terminals. Configuration data is taken from the LDAP directory on the Administration Server.
Provides AutoYaST installation and online updates for the Branch Server operating system.
Provides system redundancy and failover. A pair of Branch Servers can be configured as a two-node high availability cluster with replicated data.
Supports NTP for time synchronization from the Administration Server.
Supports SNMP. Standard MIB2 monitoring is set up with net-snmp (optional).
Logs syslog output from the Point of Service terminals (optional).

The following sections provide basic information about Branch Server structure and functions:

For information on installing and configuring the Branch Server, see Setting Up a Branch Server in the Novell Linux Point of Service 9 Installation Guide.

2.2.1 Operating System

The operating system for the Branch Server is built from a standard SLES 9 source.

If the Branch Server is required to run only the Point of Service infrastructure, it can be deployed as a control terminal running on Point of Service hardware. For more information on this configuration, see Section 2.3, POSBranch Server.

2.2.2 LDAP Branch Server Object

Each Branch Server has a corresponding Branch Server object (scBranchServer) in the LDAP directory. This object stores configuration information that is specific to each Branch Server.

For more information on the scBranchServer object, see Section 5.0, The Novell Linux Point of Service LDAP Directory.

2.2.3 LDAP Access

To complete its initial configuration and perform basic functions such as registering Point of Service terminals and downloading client images and configuration files, the Branch Server must have administrator level access to the LDAP directory. This admin account and password are created by the posInitLdap.sh or posInitEdir.sh script during the initial configuration of the Administration Server. Once created, this account is not accessible in the LDAP tree.

LDAP communications can be secured with SSL. When you run the posInitLdap.sh script, you can enable or disable SSL communication. If SSL is enabled, you must configure the scPubKey attribute in the scBranchServer object.

NOTE:The posInitEdir script does not provide SSL functionality.

2.2.4 Administrative Tasks

Other than emergency handling, no system administration is necessary on the Branch Server. All administrative tasks are controlled from the central Administration Server or are regularly executed by daemons running on the Branch Server. For emergencies and debugging, all administrative functions can be triggered locally or via SSH login by calling scripts with no or few command line parameters.

If you need to update the Point of Service images stored on the Branch Server, you can run possyncimages.pl to manually trigger the RSYNC update process and download new image files from the Administration Server. For more information, see Section A.3.10, possyncimages.pl.

NOTE:The Branch Server can simultaneously distribute SLRS 8 and Novell Linux Point of Service 9 Point of Service images.

Similarly, if you need to update the Point of Service hardware configuration information stored on the Branch Server, run either posldap2crconfig.pl --dumpall or posAdmin --updateconfig. These commands regenerate the hardware configuration and config.MAC_address files for all Point of Service terminals found in LDAP.

For more information on the posldap2crconfig.pl script, see Section A.3.5, posldap2crconfig.pl.

For more information on the posAdmin --updateconfig command, see Section 6.9, Updating config.MAC_address and Hardware Configuration Files.

2.2.5 Services

In a Novell Linux Point of Service system, Branch Servers provide the services listed in Table 2-1.

Table 2-1 Branch Server services

Service	Description
DNS	Every Branch Server runs a DNS master for that branch. The posldap2dns script generates the zone files for the BIND name server from the data in the LDAP directory and then reloads the zone files on each Branch Server.
DHCP	A DHCP server is installed on the Branch Server. The posldap2dhcp script generates the dhcpd.conf file from branch data in the LDAP directory.
NTP	The NTP service for the Branch Servers synchronizes with the Administration Server NTP, which must be configured to get time from a reliable source.
RSYNC	RSYNC is used to transfer SLRS 8 and Novell Linux Point of Service 9 images to the Branch Servers. The Branch Servers pull the images from the Administration Server by using the possyncimages script.
TFTP	The TFTP service on the Branch Server is structured with boot, image, Point of Service, and upload directories. There is a PXE default configuration with which all the Point of Service terminals first load the same initial initrd and the same kernel. For more information, see Section 2.2.7, TFTP Server Directory Structure. If there is an error with a TFTP action, the service waits 60 seconds, then restarts.
Syslog	The Branch Server can define syslog logging services for Point of Service terminals. This service must be manually defined; the configuration information is stored in the /etc/syslog.conf file, not in LDAP.

2.2.6 High Availability Configuration

For high availability, Branch Servers can be configured in two-node heartbeat pairs. The primary node runs all of the scripts and services required to download Branch Server configuration information, synchronize time, and download client images from the Administration Server. The secondary node stays synchronized with the primary, ready to take over and run the scripts and services if the primary fails.

To make the Branch Server services highly available, either the generic mechanisms of the server services (DNS, DHCP, etc.) are used or a combination of heartbeat, virtual IP, and DRDB is employed. The configuration data (DHCP leases) and application data (Point of Service application database back-end tables) are synchronized with DRBD.

For information on installing a high availability Branch Server pair, see Setting Up High Availability Branch Servers in the Novell Linux Point of Service 9 Installation Guide.

For information on adding high availability Branch Server objects to the LDAP directory, see Section 6.3.4, Adding a Branch Server with High Availability Services (scHAService) .

2.2.7 TFTP Server Directory Structure

Novell Linux Point of Service uses /tftpboot as the tftp_root path for the TFTP server on the Branch Server. Table 2-2 outlines the main areas that the directory structure is divided into under the TFTP root directory.

Table 2-2 TFTP directory structure on the Branch Server

Directory	Contents
/tftpboot/CR/	Contains config.MAC_ Address image configuration files for every registered Point of Service terminal on the current Branch Server.
/tftpboot/CR/ MAC_Address/	Contains system configuration files, such as XF86config, for the individual Point of Service terminals.
/tftpboot/boot/	Contains the following boot images and configuration files for Point of Service terminals: initrd.gz, linux, the PXE loader (pxelinux.0), and the PXE configuration folder (pxelinux.cfg).
/tftpboot/image/	Contains client image files and their checksums.
/tftpboot/upload/	Serves as the destination directory to upload hwtype.MAC_ Address files for newly registered Point of Service terminals. These files are used to create the Point of Service terminal’s workstation object in LDAP. This directory also stores the bootversion.MAC_address files that the posleases2ldap daemon uses to provide image install notification. When an image is successfully installed on a Point of Service terminal, the linuxrc script creates a bootversion.MAC_Address file in the /tftpboot/upload directory on the Branch Server. posleases2ldap then transfers the information to the scNotifiedimage attribute in the scWorkstation object in LDAP and deletes the bootversion.MAC_Address file.

An example of a Branch Server TFTP structure is shown below:

/tftpboot/CR
  00:02:55:E8:FA:C9   config.00:02:55:E8:FA:C9
  00:03:56:01:D5:5F   config.00:03:56:01:D5:5F
  00:09:6B:3B:01:07   config.00:09:6B:3B:01:07
  00:02:55:23:F3:93   config.00:02:55:23:F3:93

/tftpboot/CR/00:02:55:E8:FA:C9
  XF86Config

/tftpboot/CR/00:03:56:01:D5:5F
  XF86Config

/tftpboot/CR/00:09:6B:3B:01:07

/tftpboot/boot
  initrd.gz
  linux
  pxelinux.0
  pxelinux.cfg

/tftpboot/boot/pxelinux.cfg
  default

/tftpboot/image
  browser-2.0.21    browser-2.0.21.md5
  desktop-2.0.21    desktop-2.0.21.md5
  java-2.0.21       java-2.0.21.md5
  minimal-2.0.21    minimal-2.0.21.md5

/tftpboot/upload
  hwtype.00:02:55:E8:FA:C9

NOTE:The Point of Service control file hwtype.00:02:55:E8:FA:C9 is deleted after successful registration in LDAP. For more information, see Section 3.5.3, The hwtype.MAC_address File.