HP Certified: HP-UX System Administration

Chapter Syllabus

17.1 Devices and Physical Paths

17.2 Device Files

17.3 SCSI Device File Naming Convention

17.4 Listing Installed Devices

17.5 Creating Device Files

17.6 Installing a New Device

17.7 Terminals and Modems

HP-UX communicates with all devices through device files placed in the /dev directory. Logically, there is no difference between I/O to these files and to ordinary disk files. But these files are not like ordinary disk files in that they don't occupy any space on the disk. As soon as data are written to any of the device files, they are sent to the device represented by that file. For example, if you output some data to a printer device file, they go to an attached printer for the printing process. Any data read request from a device file is also redirected to the actual device. A read request from the modem file reads incoming data from the modem.

Most of the device files are created automatically by HP-UX. During the boot process, HP-UX probes all devices and executes /sbin/ioinit.rc scripts that create new device files if needed. If any device file is not created automatically, HP-UX provides commands to create the device files manually. These files follow a particular naming convention that indicates the hardware path a device is connected to and the type of the device. There are two major types of devices: character-type devices and block-type devices. These files also contain two special fields, listed with the ll command. These are major and minor device numbers. These numbers indicate the device driver and the encoded hardware address of that device.

In this chapter, you will be introduced to hardware paths and device files. You will see how device files in the /dev directory are arranged. You will find information about major and minor numbers, character- and block-type devices, the naming conventions used for device files, and some examples of device names . Then you will move on to how to list devices installed in your system and how to determine which devices are usable. Device drivers will be the next topic, and after that you will find information about how to install and configure new devices in your system. Finally, you will find information on modems and terminals, the device files related to them, and how they are configured.

After going through this chapter, you will be able to install and remove devices from HP-UX systems, and to diagnose and correct problems related to devices.