The Configuration Manager is a rule-driven program that automatically configures devices in the system during system boot and run time. When the Configuration Manager is invoked, it reads rules from the Configuration Rules object class and performs the indicated actions. For more information on Configuration Rules, see Configuration Rules (Config_Rules) Object Class in AIX 5L Version 5.2 Technical Reference: Kernel and Subsystems Volume 2.
Devices in the system are organized in clusters of tree structures known as nodes. Each tree is a logical subsystem by itself. For example, the system node consists of all the physical devices in the system. The top of the node is the system device. Below the bus and connected to it are the adapters. The bottom of the hierarchy contains devices to which no other devices are connected. Most pseudo-devices, including low -function terminal (LFT) and pseudo-terminal (pty) devices, are organized as separate tree structures or nodes.
See Understanding Device Dependencies and Child Devices for more information.
Each rule in the Configuration Rules (Config_Rules) object class specifies a program name that the Configuration Manager must execute. These programs are typically the configuration programs for the devices at the top of the nodes. When these programs are invoked, the names of the next lower-level devices that need to be configured are returned.
The Configuration Manager configures the next lower-level devices by invoking the configuration methods for those devices. In turn, those configuration methods return a list of to-be-configured device names. The process is repeated until no more device names are returned. As a result, all devices in the same node are configured in transverse order. The following are different types of rules:
The system boot process is divided into two phases. In each phase, the Configuration Manager is invoked. During phase 1, the Configuration Manager is called with a -f flag, which specifies that phase = 1 rules are to be executed. This results in the configuration of base devices into the system, so that the root file system can be used. During phase 2, the Configuration Manager is called with a -s flag, which specifies that phase = 2 rules are to be executed. This results in the configuration of the rest of the devices into the system.
For more information on the booting process, see Understanding System Boot Processing in AIX 5L Version 5.2 System Management Guide: Operating System and Devices.
The Configuration Manager invokes the programs in the order specified by the sequence value in the rule. In general, the lower the sequence number within a given phase, the higher the priority. Thus, a rule with a 2 sequence number is executed before a rule with a sequence number of 5. An exception is made for 0 sequence numbers, which indicate a don't-care condition. Any rule with a sequence number of 0 is executed last. The Configuration Rules (Config_Rules) object class provides an example of this process.
If device names are returned from the program invoked, the Configuration Manager finishes traversing the node tree before it invokes the next program. Note that some program names might not be associated with any devices, but they must be included to configure the system.
During system boot time, the Configuration Manager is run in two phases. In phase 1, it configures the base devices needed to successfully start the system. These devices include the root volume group, which permits the configuration database to be read in from the root file system.
In phase 2, the Configuration Manager configures the remaining devices using the configuration database from the root file system. During this phase, different rules are used, depending on whether the system was booted in normal mode or in service mode. If the system is booted in service mode, the rules for service mode are used. Otherwise, the phase 2 rules are used.
The Configuration Manager can also be invoked during run time to configure all the detectable devices that might have been turned off at system boot or added after the system boot. In this case, the Configuration Manager uses the phase 2 rules.