lsg02.htm

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

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Additional X users



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2M



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4M



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Development system



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2M



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Internet Server(FTP, WWW, WAIS, or Gopher server)



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1M



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2M



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<FONT SIZE=4 COLOR="#FF0000"><B>Hard Disks</B></FONT></CENTER></H4>



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<P>Although Linux can run completely from a floppy disk with no hard disk, running it this way doesn't offer a useful environment. Linux is designed primarily for hard disk use, and supports all the common hard disk controller systems including IDE (Integrated Drive Electronics), EIDE (Extended Integrated Drive Electronics), ESDI (Enhanced Small Device Interface), RLL (Run Length Limited), and SCSI (Small Computer System Interface). Linux supports the older 8-bit original PC controllers, although most controllers are 16-bit AT designs.



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<P>Linux is not choosy about the manufacturer and type of hard disk. As a rule, if DOS can handle the drive, so can Linux. This rule applies to all drives except SCSI drives, which require special handling. Linux still is restricted by most PC BIOS versions that impose limitations on the number of sectors, heads, and cylinders, however. There is an effective 1,024M size limit on drives with some older versions of Linux, and even some smaller drives can't be handled properly by Linux or DOS because of the BIOS. More recent versions of the operating system can overcome some of these limitations. The version of Linux on the CD-ROM accompanying this book, for example, can use disk space over the 1G limit.



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<P>Linux supports most standard SCSI devices, but not all of the many different SCSI controllers and protocols on the market work well with Linux. Linux does support the most common SCSI controllers, though. Some other controllers are supported with enhanced BIOS chips on the PC motherboard. A size limitation on the SCSI drives is still imposed by the BIOS of many early versions of Linux, so a 2G drive will only have 1G available to Linux and DOS. Other UNIX systems, like SCO UNIX, can use the rest of the drive. Later versions of Linux (mostly any kernel from version 1.1 and on) can use more than 1G of disk space on SCSI drives.



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<P>The size of disk space required by Linux depends on the parts of the operating system that are installed. A minimum effective system is 20M, which gives enough room for the basic utilities but not X. To load the entire basic Linux system, including development tools and X, provide at least 150M just for the files. Then add whatever space is required for your personal files and temporary storage for Linux. A good rule of thumb is to double the space requirements. In addition to the user space, remember to leave room for the swap space. Although the swap space size depends on what the system is used for, a good number to use is 16M.



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<P>You can use more than one drive, although you should place a bootable root Linux partition on the first drive. You also must load DOS on the first drive, although you can place partitions on other drives. The number of drives supported depend on the drive controller and BIOS. IDE systems are usually limited to two drives, but EIDE systems can handle four drives (two drives off two controllers). ESDI and RLL controllers are usually limited to two drives. SCSI controllers can handle up to seven drives per controller, and a single system can contain several controllers. SCSI is the most versatile (and also the most expensive) system.



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<P>Because hard disks are now inexpensive, obtaining large-capacity drives is relatively easy. Linux can share a disk with up to three other operating systems (more with a few tricks), so if you plan to load DOS and Linux, for example, allocate enough drive space for both operating systems.



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<P>Linux can use almost any video card that works without special drivers under DOS, including CGA, EGA, VGA, Super VGA, and Hercules video cards. Linux also supports some enhanced resolution cards, such as the Cirrus Logic, Diamond, ATI, and Trident cards. Because hundreds of video cards are available for DOS, though, not all of the available cards have drivers for Linux. Because most cards support default VGA and SVGA modes, you can use these modes in almost every case.



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<P>X can use the bitmap capabilities of a high-resolution card, although X can run on a VGA or SVGA system as well. If you are using a specialty card designed for Windows, for example, make sure that a video driver is available for Linux.



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<FONT SIZE=4 COLOR="#FF0000"><B>Mouse</B></FONT></CENTER></H4>



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<P>Linux doesn't use the mouse for character-based sessions, but it is necessary for X. Linux handles practically every type of mouse and trackball that has DOS drivers, including Microsoft, Logitech, and Mouse Systems. Linux supports both bus and serial mouses.



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<P>Linux also supports some other pointing devices, including joysticks and pen systems used for cursor movement. Some systems use a pointer pad that you can drag either your finger or a stylus across; these systems work with Linux as long as they have drivers that emulate a mouse (which most do). Finally, some touch-screens also work with Linux.



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<FONT SIZE=4 COLOR="#FF0000"><B>Tape Drives</B></FONT></CENTER></H4>



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<P>Your Linux system can use any SCSI tape drive that has a controller recognized by Linux. Other tape drives use a proprietary interface that requires a dedicated hardware card. In most cases, if the IRQ, DMA, and memory address can be configured into Linux, the tape drive should be accessible. For example, you can use some older UNIX-style tape drives, such as those made by Wangtek and Archive, under Linux even though they have a proprietary board controlling them.



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<P>Some smaller QIC (Quarter Inch Cartridge) drives are becoming popular in DOS, driven either by the floppy controller card or the parallel port. Drivers for some of these tape drives are available for Linux, although not all of these tape drives are supported. Because many of these small QIC drives rely on proprietary compression schemes to boost data density on tapes, you may not be able to write more than the raw cartridge capacity to these drives. In general, if the QIC driver runs off the floppy disk controller card and is compatible with QIC-40 or QIC-80, it will work with Linux. QIC drives that run off the parallel port do not have a driver for Linux at this time.



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<P>Because most CD-ROMs use a SCSI interface, you need either a SCSI controller card or an interface on another card, such as a sound board. Linux recognizes and supports SCSI-based CD-ROMs as long as their SCSI controller cards are recognized. If the SCSI port is on a sound board, a special driver may be required. Some IDE CD-ROMs are also available; a driver is needed for them (some drivers are included with Linux). In addition, some proprietary CD-ROM drivers, such as those found on Sound Blaster sound boards, are supported with later versions of Linux. Check the supproted hardware list available with each kernel release for a complete catalog of all supported CD-ROM drives. In general, the higher the kernel release number, the more likely a CD-ROM will be supported.



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<P>Linux can't read all formats of CD-ROMs. At the present it handles only ISO-9660 format filesystems. Although ISO-9660 is widely used, not all CD-ROMs are written using it, so don't be surprised if a DOS or Macintosh CD-ROM can't be mounted properly. Some UNIX CD-ROMs are written with proprietary formats or with Rock Ridge extensions (which allow long filenames). These CD-ROMs are usually not compatible with Linux's requirements.



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<FONT SIZE=4 COLOR="#FF0000"><B>Removable Media</B></FONT></CENTER></H4>



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<P>Removable media support in Linux depends on the type of interface the media uses. Most SCSI-based systems can be used, although the changing of media while a filesystem is loaded is seldom properly supported. Iomega's Bernoulli systems and LaserSafe Pro magneto-optical cartridge systems can all be used with Linux without special drivers, as long as the cartridges can be formatted under DOS. Some other magneto-optical and removable magnetic media systems will also function properly.



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<P>Some removable media, especially those which do not use SCSI but rely on a dedicated hardware card, require special drivers. The very limited support in Linux for these devices is mostly provided by programmers who have written a driver for their own use and then made it public domain. No commercial removable media vendors are offering Linux-specific drivers at the moment, although this situation should change as Linux becomes widespread.



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<P>Parallel and serial port printers are widely supported as dumb lineprinter devices. Although some drivers are available for specific popular printers, such as the Hewlett Packard LaserJets and DeskJets, many printers do not have dedicated drivers yet. If no driver exists for your printer, it will behave as an ASCII-only device.



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<P>There is no support at present for color printers, either laser, inkjet, or bubble-jet. A driver should be available for the most popular color printer models in the near future. Check the FTP and BBS sites (or the Linux WWW home pages) for more information.



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<P>Linux supports most serial asynchronous modems, as well as some synchronous modems. Support for ISDN modems is being developed as well. As a general rule, Linux can use any modem that DOS can use. Linux supports all baud rates, including the newer compression schemes, with some driver installation. More than one modem is supported on the system. Indeed, you can hang as many modems off a Linux system as you have serial ports.



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<P>Linux supports character-based terminals connected through a serial port or a multiport card. You can use most existing character-based terminals, and you can add any terminal for which you have the control codes. Graphics terminals, in the UNIX sense, use simple ASCII graphic characters and are not X-capable.



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<P>Some versions of Linux support X terminals, although not all X terminals work properly. X terminals typically need a very high-speed connection to properly display graphics (either through a serial port or from a network). A PC running X client software can function as an X terminal as well.



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<P>Some UNIX-based multiport cards will work with Linux, as the vendor or users have released drivers. Before purchasing a multiport card, check the availability of drivers. Some multiport cards offer expansion parallel ports as well as serial ports, and these will also need drivers.



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<P>You can connect some multiport cards through a SCSI controller card instead of building them as dedicated cards that plug into expansion slots. Even SCSI-based expansion cards will need a driver for Linux to use them properly.



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<FONT SIZE=4 COLOR="#FF0000"><B>Network Cards</B></FONT></CENTER></H4>



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<P>Because Linux is a UNIX system, its primary network protocol is TCP/IP. Other protocols can be used with Linux, but TCP/IP is the most widely used because it is included with each Linux software package and is the default network protocol. TCP/IP's role as the protocol of the Internet also makes it popular.



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<P>TCP/IP is usually used over Ethernet networks, so most of Linux's networking systems are designed around Ethernet. Many Ethernet network interface cards (NICs, also called network adapters) are available. The most popular Ethernet cards from 3Com, Novell, Western Digital, Hewlett Packard, and Intel all work cleanly with Linux. Many compatible Ethernet NICs from other vendors also function properly.



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<FONT SIZE=5 COLOR="#FF0000"><B>Where to Get Linux</B></FONT></CENTER></H3>



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<P>Linux is freely available if you know where to look. Because Linux is distributed without a central organization controlling it (as with commercial UNIX versions), no single party is responsible for keeping Linux readily and easily available. You have to find a source and make sure the version you receive has all the components, is recent, and is relatively stable. Most distribution sources have the same releases available.



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<P>You can obtain a copy of Linux in several ways; use whichever method is most convenient or economical, depending on your priorities. The most common method of obtaining a complete set of Linux binaries and utilities is through a CD-ROM. Alternatives include FTP sites and BBSs (bulletin board systems). You can also get a copy mailed to you.



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<P>The method by which you obtain Linux also dictates to some extent how complete the distribution will be. CD-ROM versions, for example, usually have every piece of Linux software available included on the disk; in contrast, some BBSs and FTP sites only offer a small distribution that is enough to install and use as a basic system. The small systems, for example, may not include the language compilers and X software.



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<P>Almost a dozen CD-ROM based distributions of Linux are available. They differ in the version that is included on the disk, their organization, and the value-added features they have, such as new installation documents and utilities as well as supporting printed manuals. Of course, you also need a CD-ROM drive on your machine that will work with Linux. Don't assume that any non-SCSI CD-ROM drive will work&#151;many of them won't!



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<P>The version you obtain should have a recent release of the Linux software (compare version numbers among CD-ROMs) as well as a complete set of accompanying utilities. It can be hard to identify the contents from the sparse identification on the cover of some CD-ROM collections, so you may find yourself unwittingly purchasing outdated material. Luckily, the CD-ROMs tend to be inexpensive. The CD-ROM included at the back of this book provides one of the most recent versions of Linux, along with many of the utilities and source libraries. With this CD-ROM, you won't need to buy another version until you want to upgrade to a later kernel.



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<P>A few vendors have dressed up their Linux collections with added utilities or boot disks that make installation much easier. The addition of precompiled games, applications, and user utilities makes these CD-ROMs a little more attractive. Some CD-ROMs also include an accompanying manual. For the most part, these manuals are simply printed versions of files on the CD-ROM, although some vendors have taken the time to write very readable instructions for Linux. If you are a newcomer to Linux, this type of document can be very useful.



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<P>File Transfer Protocol (FTP) is a widely used Internet protocol (part of the TCP/IP family) that lets you transfer files from remote machines. Several anonymous FTP sites distribute Linux software. (Anonymous means you don't need an account on the remote machine to access the files; you log in as guest or anonymous and use your name or login as a password.) If you have access to the Internet, either directly or through an on-line service provider such as CompuServe, Delphi, or America Online, you can access the Linux distribution sites.



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<P>To use FTP, you must be on a machine that supports TCP/IP. This can be your existing PC running a DOS or Windows package that gives you FTP capabilities or a UNIX or Linux workstation that is connected to an Internet service. Both ends of an FTP connection must be running a program that provides FTP services. To download a file from a remote system, you must start your FTP software and instruct it to connect to the FTP software running on the remote machine.



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<P>The Internet has many FTP archive sites. These machines are designed to allow anyone to connect to them and download software. In many cases, FTP archive sites mirror each other so that they have exactly the same software. You connect to the site that is easiest to get to. See the section in this chapter called &quot;Linux FTP Archive Sites&quot; for more information.



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<FONT SIZE=4 COLOR="#FF0000"><B>Downloading Files from a Linux FTP Site</B></FONT></CENTER></H5>



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<P>Using FTP to connect to a Linux FTP site is quite easy (assuming you have access to the Internet, of course). You must start FTP with the name of the remote system to which you want to connect. If you are directly connected to the Internet, enter the ftp command with the name of the remote site as shown in the following example: