UNIX System Administration Handbook - Evi Nemeth [77]
For more information about USB, see the site www.usb.org.
USB is a great system. We think it’s likely to gain wide acceptance in the UNIX world and to stay in use for many years to come. It has almost all the properties and features one could wish for in a low-speed bus:
• Up to 127 devices can be connected.
• Cables have only four wires: power, ground, and two signal wires.
• Connectors and connector genders are standardized.
• The connectors are small, and the cables are thin and flexible.
• Devices can be connected and disconnected without powering down.
• Signaling speeds up to 12 Mb/s are possible.
• Legacy serial and parallel devices can be connected with adaptors.
USB can even be used as a LAN technology, although it’s really not designed for that.
Unfortunately, only HP-UX provides any form of USB support as of this writing: its newest workstations use USB keyboards and mice. Linux is close behind, but its USB support is not yet fully baked. It is beyond doubt, however, that USB will soon be fully mainstream on most UNIX systems.
1. To be technically correct, this standard should now be referred to as EIA-232-E. However, no one will have the slightest idea what you are talking about.
2. At Qwest, the terms “male” and “female” are considered inappropriate. Employees are encouraged to use the words “plug” and “receptacle.” Heh heh, they said “receptacle.”
3. Dave doesn’t say this explicitly, but you must in fact wire the cable without a physical twist to achieve the “with a twist” effect. Because the connectors at the ends of a cable point away from each other, their pin numbering is automatically reversed.
4. XON and XOFF are 5. Which is not to say that you can pick your own names; most software assumes that you will use the standard naming conventions. 6. Actually, the serial ports themselves do require kernel-level configuration, but this is always done for you by the vendor. 7. On some systems, /etc/passwd is superseded or complemented by an administrative database system such as NIS. See Chapter 18 for more information. 8. .profile for sh, ksh, and bash; .cshrc and .login for csh and tcsh. 8 Adding a Disk There is never enough disk space. The minute a new disk is added to the system, it is half full; or so it seems. Getting users to clean up their disk space is as difficult as getting a teenager to clean up his room. Therefore, an administrator will occasionally have to install new disk drives. Most systems connect their disks through a standard peripheral bus called SCSI (the Small Computer Systems Interface, pronounced “scuzzy”). An alternative interface called Integrated Drive Electronics (IDE) is supported by PCs. We begin this chapter with a general discussion of the SCSI and IDE standards and the structure of modern hard disks. We then discuss the general mechanisms by which disks are formatted and partitioned and the procedure for initializing filesystems. Although most vendors use standardized disk interfaces, they seem to have made a point of using proprietary commands to set up new disks; accordingly, you’ll see a lot of vendor-specific details in this chapter. We try to cover each system in enough detail that you can at least understand the commands that are used and can locate the necessary documentation. We also illustrate each system’s installation procedure for one particular disk. 8.1 DISK INTERFACES In the beginning, computer manufacturers all defined their own proprietary interfaces for hard disks and other peripherals. This state of affairs was due in part to the immature state of interface