glbd Daemon

Purpose

Manages the global location broker database.

Syntax

/etc/ncs/glbd [ -create { -first [-family FamilyName] | -from HostName } ] [ -change_family FamilyName ] [ -listen FamilyList] [ -version ]

Description

The glbd daemon manages the global location broker (GLB) database. The GLB database, part of the Network Computing System (NCS), helps clients to clients to locate servers on a network or internet. The GLB database stores the locations (specifically, the network addresses and port numbers) of servers on which processes are running. The glbd daemon maintains this database and provides access to it.

There are two versions of the GLB daemon, glbd and nrglbd.

You can replicate the GLB database to increase its availability. Copies of the database can exist on several hosts, with a glbd running on each of those hosts to maintain the consistency of the database replicas. (In an internet, at least one glbd must be running in each network.) Each replica of the GLB keeps a list of all the other GLB replicas. The drm_admin tool administers the replication of the GLB database and of the replica list.

Currently, glbd supports both the DARPA IP and Domain DDS network protocols. A GLB replica can allow access to its database from both IP and DDS clients. However, when communicating with each other to maintain replication of the GLB database, GLB replicas should use only one protocol family. You choose which family the GLBs will use. In an internet, all routing nodes must support this family.

The glbd daemon can be started in one of two ways:

Through the System Resource Controller (the recommended method), by entering on the command line:
```
startsrc -s glbd
```
By a person with root user authority entering on the command line:
```
/etc/ncs/glbd &
```

TCP/IP must be configured and running on your system before starting the glbd daemon. The llbd daemon must also be started and running before you start the glbd daemon.

Flags

Item	Description
-create	Creates a replica of the GLB. This option creates a GLB database in addition to starting a broker process. It must be used with either -first or -from. -first Creates the first replica (that is, the very first instance) of the GLB on your network or internet. This option can be used only with the -create option. -family FamilyName Specifies the address family that the first GLB replica will use to identify itself on the replica list. This option can be used only in conjunction with the -first option. Any subsequently created replicas must use this family to communicate with this replica. Currently, FamilyName can be either dds or ip. If this option is not used, the replica will be identified on the replica list by its DDS address. -from HostName Creates additional replicas of the GLB. This option can be used only with the -create option. A replica of the GLB must exist at HostName. The database and replica list for the new replica are initialized from those at HostName. The replica at HostName adds an entry for the new replica to its replica list and propagates the entry to the other GLB replicas. A HostName takes the form family:host, where the host can be specified either by its name or by its network address. For example, `ip:jeeves`, `ip:bertie`, and `ip:#192.5.5.5` are acceptable host names. The new replica will use the same address family as HostName in identifying itself on the replica list. For example, if HostName is an IP address, the new replica will be listed by its IP address on the replica list.
-change_family FamilyName	Changes the address family of every GLB replica. Use this option only if network reconfigurations require that you make such a change. Currently, FamilyName can be either dds or ip.
-listen FamilyList	Restricts the address families on which a GLB listens. Use it only if you are creating a special configuration where access to a GLB is restricted to a subset of hosts in the network or internet. The FamilyList is a list of the address families on which the GLB will listen. Names in this list are separated by spaces. Possible family names include dds and ip. The GLB will always listen for requests from the family by which it is listed on the replica list, even if that family is not specified in FamilyList. If glbd is started without the -listen option, the GLB will listen on all address families that are supported both by NCS and by the local host. On Apollo systems, this set of families always includes dds and may also include ip. On most other systems, ip is currently the only family.
-version	Displays the version of NCS that this glbd belongs to, but does not start the daemon.

Files

Item	Description
/etc/ncs/glb_log	Contains diagnostic output from glbd.
/etc/rc.ncs	Contains commands to start the NCS daemons.

Examples

Create and start for the first time the first replica of the GLB on this network or internet:
```
/etc/ncs/glbd -create -first -family ip &
```
Start for the first time a subsequent replica of the GLB, initializing its database from host jeeves:
```
/etc/ncs/glbd -create -from ip:jeeves &
```
Restart an existing replica of the GLB:
```
/etc/ncs/glbd & 
```