diff options
Diffstat (limited to 'sag-0.6.1-www/Invisible/sag-0.6/node34.html')
| -rw-r--r-- | sag-0.6.1-www/Invisible/sag-0.6/node34.html | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/sag-0.6.1-www/Invisible/sag-0.6/node34.html b/sag-0.6.1-www/Invisible/sag-0.6/node34.html new file mode 100644 index 0000000..881fcbc --- /dev/null +++ b/sag-0.6.1-www/Invisible/sag-0.6/node34.html @@ -0,0 +1,151 @@ +<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> +<!--Converted with LaTeX2HTML 96.1-h (September 30, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds --> +<HTML> +<HEAD> +<TITLE>Formatting</TITLE> +<META NAME="description" CONTENT="Formatting"> +<META NAME="keywords" CONTENT="sag"> +<META NAME="resource-type" CONTENT="document"> +<META NAME="distribution" CONTENT="global"> +<LINK REL=STYLESHEET HREF="sag.css"> +</HEAD> +<BODY LANG="EN" > + <A NAME="tex2html740" HREF="node35.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html738" HREF="node28.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html732" HREF="node33.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html742" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html743" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html741" HREF="node35.html">Partitions</A> +<B>Up:</B> <A NAME="tex2html739" HREF="node28.html">Using Disks and Other </A> +<B> Previous:</B> <A NAME="tex2html733" HREF="node33.html">Tapes</A> +<BR> <P> +<H1><A NAME="SECTION00560000000000000000">Formatting</A></H1> +<P> + <b>Formatting</b> is the process of writing marks on the + magnetic media that are used to mark tracks and sectors. + Before a disk is formatted, its magnetic surface is a complete + mess of magnetic signals. When it is formatted, some order is + brought into the chaos by essentially drawing lines where the + tracks go, and where they are divided into sectors. The + actual details are not quite exactly like this, but that is + irrelevant. What is important is that a disk cannot be used + unless it has been formatted. +<P> + The terminology is a bit confusing here: in MS-DOS, the word + formatting is used to cover also the process of creating a + filesystem (which will be discussed below). There, the two + processes are often combined, especially for floppies. When + the distinction needs to be made, the real formatting is + called <b>low-level formatting</b>, while making the filesystem + is called <b>high-level formatting</b>. In UNIX circles, + the two are called formatting and making a filesystem, so + that's what is used in this book as well. +<P> + For IDE and some SCSI disks the formatting is actually + done at the factory and doesn't need to be repeated; hence + most people rarely need to worry about it. In fact, + formatting a hard disk can cause it to work less well, for + example because a disk might need to be formatted in some very + special way to allow automatic bad sector replacement to work. +<P> + Disks that need to be or can be formatted often require a special + program anyway, because the interface to the formatting logic + inside the drive is different from drive to drive. The + formatting program is often either on the controller BIOS, or + is supplied as an MS-DOS program; neither of these can easily be used + from within Linux. +<P> + During formatting one might encounter bad spots on the disk, + called <b>bad blocks</b> or <b>bad sectors</b>. These are sometimes + handled by the drive itself, + but even then, if more of them develop, something needs to be + done to avoid using those parts of the disk. The logic to do + this is built into the filesystem; how to add the information + into the filesystem is described below. Alternatively, one + might create a small partition that covers just the bad part + of the disk; this approach might be a good idea if the bad + spot is very large, since filesystems can sometimes have + trouble with very large bad areas. +<P> + Floppies are formatted with <tt>fdformat</tt><A NAME="1489"> </A>. The floppy device + file to use is given as the parameter. For example, the + following command would format a high density, + 3.5 inch floppy in the first floppy drive: + <BLOCKQUOTE> <TT> +<code>$</code> <I>fdformat /dev/fd0H1440</I> <BR> +<code>Double-sided, 80 tracks, 18 sec/track. Total capacity 1440 kB.</code> <BR> +<code>Formatting ... done</code> <BR> +<code>Verifying ... done</code> <BR> +<code>$ </code> + </TT></BLOCKQUOTE> + Note that if you want to use an autodetecting device (e.g., + <tt>/dev/fd0</tt><A NAME="1491"> </A>), you <EM>must</EM> set the parameters of the device + with <tt>setfdprm</tt><A NAME="1493"> </A> first. To achieve the same effect as + above, one would have to do the following: + <BLOCKQUOTE> <TT> +<code>$</code> <I>setfdprm /dev/fd0 1440/1440</I> <BR> +<code>$</code> <I>fdformat /dev/fd0</I> <BR> +<code>Double-sided, 80 tracks, 18 sec/track. Total capacity 1440 kB.</code> <BR> +<code>Formatting ... done</code> <BR> +<code>Verifying ... done</code> <BR> +<code>$ </code> + </TT></BLOCKQUOTE> + It is usually more convenient to choose the correct device file + that matches the type of the floppy. Note that it is unwise to + format floppies to contain more information than what they are + designed for. +<P> + <tt>fdformat</tt><A NAME="1495"> </A> will also validate the floppy, i.e., check it + for bad blocks. It will try a bad block several times (you + can usually hear this, the drive noise changes dramatically). + If the floppy is only marginally bad (due to dirt on the + read/write head, some errors are false signals), <tt>fdformat</tt><A NAME="1497"> </A> won't + complain, but a real error will abort the validation process. + The kernel will print log messages for each I/O error it + finds; these will go to the console or, if <tt>syslog</tt><A NAME="1499"> </A> + is being used, to the file <tt>/usr/adm/messages</tt><A NAME="1501"> </A>. <tt>fdformat</tt><A NAME="1503"> </A> + itself won't tell where the error is (one usually doesn't care, + floppies are cheap enough that a bad one is automatically thrown + away). + <BLOCKQUOTE> <TT> +<code>$</code> <I>fdformat /dev/fd0H1440</I> <BR> +<code>Double-sided, 80 tracks, 18 sec/track. Total capacity 1440 kB.</code> <BR> +<code>Formatting ... done</code> <BR> +<code>Verifying ... read: Unknown error</code> <BR> +<code>$ </code> + </TT></BLOCKQUOTE> +<P> + The <tt>badblocks</tt><A NAME="1505"> </A> command can be used to search any disk or + partition for bad blocks (including a floppy). It does not + format the disk, so it can be used to check even existing + filesystems. The example below checks a 3.5 inch + floppy with two bad blocks. + <BLOCKQUOTE> <TT> +<code>$</code> <I>badblocks /dev/fd0H1440 1440</I> <BR> +<code>718</code> <BR> +<code>719</code> <BR> +<code>$ </code> + </TT></BLOCKQUOTE> + <tt>badblocks</tt><A NAME="1507"> </A> outputs the block numbers of the bad blocks it finds. + Most filesystems can avoid such bad blocks. They maintain a list + of known bad blocks, which is initialized when the filesystem is + made, and can be modified later. The initial search for bad + blocks can be done by the <tt>mkfs</tt><A NAME="1509"> </A> command (which initializes + the filesystem), but later checks should be done with + <tt>badblocks</tt><A NAME="1511"> </A> and the new blocks should be added with + <tt>fsck</tt><A NAME="1513"> </A>. We'll describe <tt>mkfs</tt><A NAME="1515"> </A> and <tt>fsck</tt><A NAME="1517"> </A> later. +<P> + Many modern disks automatically notice bad blocks, and attempt + to fix them by using a special, reserved good block instead. + This is invisible to the operating system. This feature should + be documented in the disk's manual, if you're curious if it + is happening. Even such disks can fail, if the number of bad + blocks grows too large, although chances are that by then the disk + will be so rotten as to be unusable. +<P> +<HR><A NAME="tex2html740" HREF="node35.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="./next_motif.gif"></A> <A NAME="tex2html738" HREF="node28.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="./up_motif.gif"></A> <A NAME="tex2html732" HREF="node33.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="./previous_motif.gif"></A> <A NAME="tex2html742" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="./contents_motif.gif"></A> <A NAME="tex2html743" HREF="node114.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="./index_motif.gif"></A> <BR> +<B> Next:</B> <A NAME="tex2html741" HREF="node35.html">Partitions</A> +<B>Up:</B> <A NAME="tex2html739" HREF="node28.html">Using Disks and Other </A> +<B> Previous:</B> <A NAME="tex2html733" HREF="node33.html">Tapes</A> +<P><ADDRESS> +<I>Lars Wirzenius <BR> +Sat Nov 15 02:32:11 EET 1997</I> +</ADDRESS> +</BODY> +</HTML> |