System Management Concepts: Operating System and Devices

Devices for BSD 4.3 System Managers

A device on a 4.3 BSD system is accessible to an application only when:

• The device is physically installed and functioning.
• The driver for the device is in the kernel.
• The device special files for the device exist in the /dev directory.

A device on this operating system is accessible to an application only when:

• The device is physically installed and functioning.
• The driver for the device is in the kernel or in a loaded kernel extension.
• The device special files for the device exist in the /dev directory.
• The object database in the /etc/objrepos directory contains entries for the device that match the physical configuration.

The device specific programs called methods, found in the /etc/methods directory, maintain the object database. The methods are invoked by the Configuration Manager (accessed through the cfgmgr command) and other commands.

If a device can no longer be accessed by an application program, it can mean that the hardware is faulty or it can mean that the configuration database in the /etc/objrepos directory is damaged.

The cfgmgr command processes the configuration database in the /etc/objrepos directory and is processed at startup time by the cfgmgr command (the Configuration Manager).

The pseudocode below shows the Configuration Manager logic:

/* Main */
While there are rules in the Config_Rules database
        {
        Get the next rule and execute it
        Capture stdout from the last execution
        Parse_Output(stdout)
        }
/* Parse Output Routine */
/* stdout will contain a list of devices found */
Parse_OutPut(stdout)
        {
        While there are devices left in the list
                {
                Lookup the device in the database
                if (!defined)
                        Get define method from database and execute
                if (! configured)
                        {
                        Get config method from database and execute
                        Parse_Output(stdout)
                         }
                }
        }