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diff --git a/sag-0.6.1-www/sag-0.6.1.html/c701.html b/sag-0.6.1-www/sag-0.6.1.html/c701.html new file mode 100644 index 0000000..0e9b325 --- /dev/null +++ b/sag-0.6.1-www/sag-0.6.1.html/c701.html @@ -0,0 +1,385 @@ +<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN"> +<HTML +><HEAD +><TITLE +>Using Disks and Other Storage Media</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet"><LINK +REL="HOME" +TITLE="The Linux System Administrators' Guide" +HREF="book1.html"><LINK +REL="PREVIOUS" +TITLE="The /proc filesystem" +HREF="x595.html"><LINK +REL="NEXT" +TITLE="Hard disks" +HREF="x747.html"></HEAD +><BODY +BGCOLOR="#FFFFFF" +TEXT="#000000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>The Linux System Administrators' Guide</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x595.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +></TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x747.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="CHAPTER" +><H1 +><A +NAME="AEN701" +>Chapter 4. Using Disks and Other Storage Media</A +></H1 +><DIV +CLASS="TOC" +><DL +><DT +><B +>Table of Contents</B +></DT +><DT +><A +HREF="c701.html#AEN721" +>Two kinds of devices</A +></DT +><DT +><A +HREF="x747.html" +>Hard disks</A +></DT +><DT +><A +HREF="x787.html" +>Floppies</A +></DT +><DT +><A +HREF="x801.html" +>CD-ROM's</A +></DT +><DT +><A +HREF="x811.html" +>Tapes</A +></DT +><DT +><A +HREF="x817.html" +>Formatting</A +></DT +><DT +><A +HREF="x876.html" +>Partitions</A +></DT +><DT +><A +HREF="x1029.html" +>Filesystems</A +></DT +><DT +><A +HREF="x1366.html" +>Disks without filesystems</A +></DT +><DT +><A +HREF="x1384.html" +>Allocating disk space</A +></DT +></DL +></DIV +><BLOCKQUOTE +><P +>“On a clear disk you can seek forever. + ”</P +></BLOCKQUOTE +><P +>When you install or upgrade your system, you need to do a + fair amount of work on your disks. You have to make filesystems + on your disks so that files can be stored on them and reserve + space for the different parts of your system.</P +><P +>This chapter explains all these initial activities. Usually, + once you get your system set up, you won't have to go through + the work again, except for using floppies. You'll need to come + back to this chapter if you add a new disk or want to fine-tune + your disk usage.</P +><P +> </P +><P +>The basic tasks in administering disks are: + + <P +></P +><UL +><LI +><P +> Format your disk. This does various things to prepare it for + use, such as checking for bad sectors. (Formatting is nowadays + not necessary for most hard disks.)</P +></LI +><LI +><P +> Partition a hard disk, if you want to use it for several + activities that aren't supposed to interfere with one another. + One reason for partitioning is to store different operating + systems on the same disk. Another reason is to keep user + files separate from system files, which simplifies back-ups + and helps protect the system files from corruption. + </P +></LI +><LI +><P +> Make a filesystem (of a suitable type) on each disk or partition. + The disk means + nothing to Linux until you make a filesystem; then files can + be created and accessed on it. + </P +></LI +><LI +><P +> Mount different filesystems to form a single tree structure, either + automatically, or manually as needed. (Manually mounted filesystems + usually need to be unmounted manually as well.) + </P +></LI +></UL +> + + </P +><P +><A +HREF="c1450.html" +>Chapter 5</A +> contains information + about virtual memory and disk caching, of which you also need + to be aware when using disks.</P +><DIV +CLASS="SECT1" +><H1 +CLASS="SECT1" +><A +NAME="AEN721" +>Two kinds of devices</A +></H1 +><P +>UNIX, and therefore Linux, recognizes two different + kinds of device: random-access block devices (such as disks), + and character devices (such as tapes and serial lines), + some of which may be serial, and some random-access. Each + supported device is represented in the filesystem as a + <I +CLASS="GLOSSTERM" +>device file</I +>. + When you read or write a device file, the + data comes from or goes to the device it represents. This way + no special programs (and no special application programming + methodology, such as catching interrupts or polling a serial + port) are necessary to access devices; for example, to send a + file to the printer, one could just say + +<PRE +CLASS="SCREEN" +><TT +CLASS="PROMPT" +>$</TT +> <TT +CLASS="USERINPUT" +><B +>cat filename > /dev/lp1</B +></TT +> +<TT +CLASS="PROMPT" +>$</TT +></PRE +> + + and the contents of the file are printed (the file must, of + course, be in a form that the printer understands). However, + since it is not a good idea to have several people cat their + files to the printer at the same time, one usually uses a special + program to send the files to be printed (usually <B +CLASS="COMMAND" +>lpr</B +>). + This program makes sure that only one file is being printed + at a time, and will automatically send files to the printer as + soon as it finishes with the previous file. Something similar + is needed for most devices. In fact, one seldom needs to worry + about device files at all.</P +><P +>Since devices show up as files in the filesystem (in the + <TT +CLASS="FILENAME" +>/dev</TT +> directory), it is easy + to see just what device files exist, using <B +CLASS="COMMAND" +>ls</B +> or + another suitable command. In the output of <B +CLASS="COMMAND" +>ls -l</B +>, the + first column contains the type of the file and its + permissions. For example, inspecting a serial device + gives on my system + +<PRE +CLASS="SCREEN" +><TT +CLASS="PROMPT" +>$</TT +> <TT +CLASS="USERINPUT" +><B +>ls -l /dev/cua0</B +></TT +> +<TT +CLASS="COMPUTEROUTPUT" +>crw-rw-rw- 1 root uucp 5, 64 Nov 30 1993 /dev/cua0</TT +> +<TT +CLASS="PROMPT" +>$</TT +></PRE +> + + The first character in the first column, i.e., + `<TT +CLASS="LITERAL" +>c</TT +>' in <TT +CLASS="LITERAL" +>crw-rw-rw-</TT +> + above, tells an informed user the type of the file, in this + case a character device. For ordinary files, the first + character is `<TT +CLASS="LITERAL" +>-</TT +>', for directories + it is `<TT +CLASS="LITERAL" +>d</TT +>', and for block devices + `<TT +CLASS="LITERAL" +>b</TT +>'; see the <B +CLASS="COMMAND" +>ls</B +> man page + for further information.</P +><P +>Note that usually all device files exist even though the + device itself might be not be installed. So just because you + have a file <TT +CLASS="FILENAME" +>/dev/sda</TT +>, it doesn't mean that you really do + have an SCSI hard disk. Having all the device files makes the + installation programs simpler, and makes it easier to add new + hardware (there is no need to find out the correct parameters + for and create the device files for the new device).</P +></DIV +></DIV +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x595.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="book1.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x747.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>The <TT +CLASS="FILENAME" +>/proc</TT +> filesystem</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +> </TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>Hard disks</TD +></TR +></TABLE +></DIV +></BODY +></HTML +>
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