path: root/gnome-users-guide/gnome-users-guide-1.4/C/newbies.sgml

<appendix id="newbies" label="A"> 
  <title> If you are new to Linux/UNIX</title>
  
  <para> One of the goals of GNOME is to make your system easy to use,
    without requiring you to learn the syntax of most UNIX commands.
    However, there are some basic UNIX notions that you have to be
    familiar with, even while using the easy graphical interface
    provided by GNOME. For the convenience of new users, these basics
    are collected in this appendix. If you need further information on
    UNIX, you should read the documentation which came with your
    system; there are also a number of books and on-line guides
    available for all versions of UNIX. 
  </para>

  <para> The following guide applies to all versions of UNIX and
    UNIX-like operating systems, including both the commercial Unices
    such as <systemitem>Solaris</systemitem> and open-source operating
    systems such as <systemitem>FreeBSD</systemitem> and
    <systemitem>Linux</systemitem>. Some of the material here is based
    on <citetitle>Linux Installation and Getting Started</citetitle>
    guide, by Matt Welsh, Phil Hughes, David Bandel, Boris Beletsky,
    Sean Dreilinger, Robert Kiesling, Evan Liebovitch, and Henry
    Pierce. The guide is available for download or online viewing from
    the <ulink url="http://www.linuxdoc.org" type="http">Linux
    Documentation Project</ulink> or from the <ulink
    url="http://www.oswg.org">Open Source Writers Group</ulink>.
  </para>
  <sect1 id="new-users">
    <title>Users</title> 
    <para> UNIX is a multiuser operating system: it
      was designed to allow many users to work on the same computer,
      either simultaneously (using several terminals or network
      connections) or in turns. Under UNIX, to identify yourself to
      the system, you must log in, which entails entering your
      <emphasis>login name</emphasis> (the name the system uses to identify
      you) and your <emphasis>password</emphasis>, which is your personal key
      for logging in to your account. Because only you know your
      password, no one else can log in to the system under your user
      name. Usually people choose their first or last name or some
      variation of it as their login name, so that if your real name
      is Sasha Beilinson, your login might be <systemitem>sasha</systemitem>.
    </para>
    <para> Each user has a separate place to keep his files (called
      his <emphasis>home directory</emphasis>). UNIX has a system of
      permissions (see <xref linkend="permissions">), so that on a
      properly configured UNIX system a user can't change other users'
      or system files. This also allows every user to customize
      various aspects of the system &mdash; in particular, GNOME
      behavior &mdash; for himself, without affecting other users.
    </para>
    <para> On any UNIX system there is also a special user, called
      <emphasis>system administrator</emphasis>, with the login name
      <systemitem>root</systemitem>. He has <emphasis>full</emphasis>
      control over the system &mdash; including full access to all the
      system and users' files. He has the authority to change the
      passwords of existing users and add new users, install and
      uninstall software, and so on. The system administrator is
      usually the person responsible for proper functioning of the
      system, so if you have some problems, you should ask him.
    </para>
    <important>
      <title>IMPORTANT</title>
      <para>
	Even if you are the only user on your computer (for example,
	if the computer is your personal workstation), so that you are
	also the system administrator, it is important that you create
	a user account and use it for daily work, logging in as root
	only when necessary for system maintenance. Because root can
	do anything, it is easy to make mistakes that have
	catastrophic consequences.  Picture the root account as a
	magic hat that gives you lots of power, with which you can, by
	waving your hands, create or destroy entire cities.  Because
	it is easy to wave your hands in a destructive manner, it is
	not a good idea to wear the magic hat when it is not needed,
	despite the wonderful feeling.
      </para>
    </important>
  </sect1>
  <sect1 id="new-file">
    <title>Files and filenames</title>
    <para>
      Under most operating systems (including UNIX), there is the
      concept of a <emphasis>file</emphasis>, which is just a bundle of
      information given a name (called a
      <emphasis>filename</emphasis>). Examples of files might be
      your history term paper, an e-mail message, or an actual
      program that can be executed. Essentially, anything saved on
      disk is saved in an individual file.
    </para>
    <sect2 id="new-filenames">
      <title>Filenames</title>
      <para>
	Files are identified by their filenames. For example, the file
	containing your conference talk might be saved with the filename
	<filename>talk.txt</filename>. There is no standard format for file
	names as there is under MS-DOS and some other operating systems; in
	general, a filename can contain any character (except the /
	character&ndash;see the discussion of path names below) and is
	limited to 256 characters in length.
      </para>
      <important>
	<title>IMPORTANT</title>
	<para>
	  Unlike MS-DOS, the filenames in UNIX are case-sensitive:
	  <filename>myfile.txt</filename> and
	  <filename>MyFile.txt</filename> are considered as two
	  different files.
	</para>
      </important>
      <para>
	You should also be aware of several UNIX conventions; while they are
	not mandatory, it is usually a good idea to follow them.
	<itemizedlist>
	  <listitem>
	    <para> It is customary to use the format
	      <filename>filename.extension</filename> for filenames, where the
	      extension indicates the file type; for example, the
	      extension <filename>txt</filename> is usually used for plain
	      text files, while the extension <filename>jpeg</filename> is
	      used for graphics in JPEG format, and so on. In
	      particular, the <application>Nautilus File
		Manager</application> (<application>Nautilus</application>)
	      uses extensions to determine file type. You can view all
	      the file extensions recognized by
	      <application>Nautilus</application> by choosing the
	      <guimenuitem>File types and Programs</guimenuitem> capplet in the
	      <guimenu>Document Handlers</guimenu> section of the
	      <application>Control-center</application>. Note that the standard
	      convention in UNIX is that the
	      <emphasis>executables</emphasis> (i.e., the program
	      files) have no extension at all.
            </para>
          </listitem>
	  
	  <listitem>
	    <para> Files and directories whose names begin with a dot
	      (.) are usually <emphasis>configuration
		files</emphasis>, that is, files which keep settings and
	      preferences for various applications. For example, GNOME
	      keeps all its settings in various files in the directories
	      <filename>.gnome</filename> and
	      <filename>.gnome-desktop</filename> in the user's home
	      directory. Since most of the time you do not need to
	      edit these files manually, or even know their precise
	      names and locations, <application>Nautilus</application>
	      usually doesn't show these files. You can change this
	      setting using the <guimenuitem>Preferences</guimenuitem> dialog.
	    </para>
	  </listitem>
	  
	  <listitem> 
	    <para> Files with names ending with tilde (~) are
	      usually backup files created by various
	      applications. For example, when you edit a file
	      <filename> myfile.txt</filename> with
	    <application>emacs</application>, it 
	      saves the previous version in the file
	      <filename>myfile.txt~</filename>. Again, you can control whether
	      you want Nautilus File Manager to show these files or not
	      in <guimenuitem>Preferences</guimenuitem> dialog.
	    </para>
	  </listitem>
	</itemizedlist>
      </para>
    </sect2>
    <sect2 id="new-wildcards">
      <title> Wildcards</title> 

      <para>When entering commands from the command line, you can use
	so-called <emphasis>wildcards</emphasis> instead of an exact
	filename. The most common wildcard is *, which matches any
	sequence of symbols (including an empty string). For example,
	the command <command>ls *.txt</command> will list all the files with
	the extension <filename>txt</filename>, and the command <command>rm
	  chapter*</command> will remove all files with the names starting with
	<filename>chapter</filename> (<command>ls</command> and
	<command>rm</command> are UNIX 
	commands for listing and removing files). Another useful
	wildcard is ?, which matches any single symbol: for example,
	<command>rm chapter?.txt</command> will remove files
	<filename>chapter1.txt, chapter2.txt</filename> , but not
	<filename>chapter10.txt</filename>
      </para>
      </sect2>

    <sect2 id="quoting">
      <title>Using spaces, commas, etc. in file names</title>
      <para>
	As was mentioned above, a file name may contain not only
	letters and numbers, but also spaces, commas, etc. - any
	characters other than slash (/). However, if you are using
	commands typed on the command line, you should be careful when
	dealing with such files. For example, if you have a file named
	<filename>My  file</filename>, and you want to delete it,
	typing <command>rm My file</command> will not give the desired
	effect: the command <command>rm</command> will assume that you
	want to remove files <filename>My</filename> and
	<filename>file</filename>. At best, it will give you an error
	message; at worst (if you do have a file named
	<filename>My</filename>) it will remove a wrong file. The
	right way to do this is to enclose the file name in single
	quotes: <command>rm 'My File'</command>. The same  should be
	done for file names  containing any symbols that are normally
	considered as "separators", or have some special meaning; this
	includes comma (,), star (*), question mark (?), and more. To
	be on the safe side, quote in this way all file names that
	contain anything other than letters, numbers, and
	dots. </para>
      <para>
	Of course, if you are only using graphical tools such as Nautilus
	File Manager, than you do not  need to worry about this: to
	delete file <filename>My file</filename>, just drag it to the
	trash can.
      </para>
    </sect2>

  </sect1>
  <sect1 id="new-dirs">
    <title>Directories and paths</title> 
    <sect2 id="new-dirstruct">
      <title>Directory structure</title>
      <para>
	Now, let's discuss the concept of directories. A
	<emphasis>directory</emphasis> is a collection of files. It
	can be thought of as a "folder" that contains many different
	files. Directories are given names, with which they can be
	identified. Furthermore, directories are maintained in a
	tree-like structure; that is, directories may contain other
	directories. The top level directory is called the "root
	directory" and denoted by <filename>/</filename>; it contains
	all the files in your system.
      </para>
      <sect3 id="new-path">
	<title>Pathnames</title>
	<para>
	  A <emphasis>pathname</emphasis> is a file's "full name"; it
	  contains not only filename but also its locaion. It is
	  made up of the filename, preceded by the name of the
	  directory containing that file. This, in turn, is preceded
	  by the name of directory containing <emphasis>that
	  directory</emphasis>, and so on. A typical pathname may
	  look like <filename>/home/sasha/talk.txt</filename> which
	  refers to the file <filename>talk.txt</filename> in the
	  directory <filename>sasha</filename> which in turn is a
	  subdirectory in <filename>/home</filename>.
	</para>
	<para>
	  As you can see, the directory and filename are separated by
	  a single slash (/). For this reason, filenames themselves
	  cannot contain the / character.  MS-DOS users will find this
	  convention familiar, although in the MS-DOS world the
	  backslash (\) is used instead. The directory that contains a
	  given subdirectory is known as the <emphasis>parent
	  directory</emphasis>. Here, the directory
	  <filename>home</filename> is the parent of the directory
	  <filename>sasha</filename>.
	</para>
	<para>
	  Each user has a home directory, which is the directory set aside for
	  that user to store his or her files.  Usually, user home directories
	  are contained under <filename>/home</filename>, and are named for the
	  user owning that directory, so that the home directory of user
	  <systemitem>sasha</systemitem> would be 
	  <filename>/home/sasha</filename>.
	</para>
      </sect3>
    </sect2>
    <sect2 id="new-relative"> 
      <title>Relative directory names</title>
      <para>
	At any moment, commands that you enter are assumed to be
	<emphasis>relative</emphasis> to your current working
	directory. You can think of your working directory as the
	directory in which you are currently ``located''. When you
	first log in, your working directory is set to your home
	directory &mdash; for user sasha, it would be
	<filename>/home/sasha</filename>. Whenever you refer to a
	file, you may refer to it in relationship to your current
	working directory, rather than specifying the full pathname of
	the file.
      </para>
      <para>
	For example, if your current directory is
	<filename>/home/sasha</filename>, and you have a file there called
	<filename>talk.txt</filename>, you can refer to it just by its file
	name: a command like <command>emacs talk.txt</command> issued from the
	directory <filename>/home/sasha</filename> is equivalent to
	<command>emacs /home/sasha/talk.txt</command>
	(<application>emacs</application> is an extremely powerful editor for
	text files; new users may prefer something simpler, such as
	<application>gnotepad</application>, but for power user,
	<application>emacs</application> is indispensable).
      </para>


      <para>
	Similarly, if, in <filename>/home/sasha</filename> you have a
	subdirectory called <filename>papers</filename> and, in that
	subdirectory, a file called <filename>fieldtheory.txt</filename>, you
	can refer to it as <filename>papers/fieldtheory.txt</filename>.
      </para>
      <para> If you begin a filename (like
	<filename>papers/fieldtheory.txt</filename>) with a character
	other than /, you're referring to the file in terms relative
	to your current working directory. This is known as a relative
	pathname.  On the other hand, if you begin a filename with a
	/, the system interprets this as a full pathname &mdash; that
	is, a pathname that includes the entire path to the file,
	starting from the root directory, /. Use of the full pathname
	is known as an <emphasis>absolute pathname</emphasis>.
      </para>
    </sect2>
    <sect2 id="new-path-conv">
      <title>Pathname conventions</title> 
      <para>
	Here are some standard conventions you can use in paths: 
      </para>
      <para>
	<filename>~/</filename> &mdash; user's home directory
      </para>
      <para>
	<filename>./</filename>  &mdash; current working directory
      </para>
      <para>
	<filename>../</filename>  &mdash; parent of the current directory
      </para>
      <para>
	For example, if sasha's current directory is
	<filename>/home/sasha/papers</filename>, he can refer to the file
	<filename>/home/sasha/talk.txt</filename> as
	<filename>~/talk.txt</filename> or as <filename>../talk.txt</filename>.
      </para>
    </sect2>
  </sect1>
  <sect1 id="permissions">
    <title>Permissions</title>
    <para>
      Every file on your system has an <emphasis>owner</emphasis> &mdash; one
      of the users (usually the one who created this file), and a system of
      <emphasis>permissions</emphasis>, which regulate access to this
      file.
    </para>
    <para>
      For ordinary files, there are 3 types of access permissions:
      read, write, and execute (the latter only makes sense for
      executable files). They can be set independently for 3
      categories of users: the file owner, the users in the group
      owning the file, and everyone else. Discussion of groups of
      users goes beyond the scope of this document; the other two
      categories are self-explanatory.  <!--Which groups of users? I
      don't think the other two categories are self-explanatory. Would
      help if there was some exposition here which explicitly states
      who belongs where.-->So, if the permissions on a file
      <filename>/home/sasha/talk.txt</filename> are set to read and
      write for user sasha, who is the file owner, and read only for
      everyone else, only sasha will be able to modify this file.
      <!--How about adding something in parentheses here, like (Since
      sasha created the file <filename>talk.txt</filename>, sasha has
      the widest range of rights to access the file.)... or something
      like that?-->
    </para>

    <para>
      All newly created files carry some standard permissions, 
      usually read/write for user and read only for
      everyone else. You can view the permissions using the Nautilus File
      Manager, by right-clicking on the file, choosing
      <guimenuitem>Show Properties</guimenuitem> in the pop-up menu, and then the
      <guilabel>Permissions</guilabel> tab. Using this dialog, you can also
      change the permissions &mdash; just click on a square
      representing the permission to toggle it.  Of course, only the
      file owner or the system administrator can change the
      permissions of a file. Advanced users can also  change the default
      file permissions which are assigned to newly created
      files&mdash;see the manual pages for your default shell (usually
      <command>bash</command>,
      <command>csh</command> or <command>tcsh</command>) and look for the command
      <command>umask</command>.  
    </para>

    <para>
      A file can also have some special permission properties such
      as UID, GID, and "sticky" bit. They are for experienced users
      only &mdash; do not change them unless you know what you are
      doing. (If you are curious: these permissions are typically
      used on executable files to allow the user to execute
      <emphasis>some</emphasis>  commands
      which read or modify  files to which the user himself doesn't
      have access.) 
    </para>

    <para> Similar to files, the directories also have
      permissions. Again, there are  3 possible
      permissions: read, write, and execute. However, they have
      different meaning: namely, "read" permission for a directory
      means permission to list the contents of the directory or
      search for a file; "write" means permission to create and
      remove files in the directory, and "execute" means permission
      to access files in the directory. 
    </para>
    <para>
      Note that the permissions granted to a file depend on the
      permissions of the directory in which the file is located: in
      order to be able to read a file, a user needs to have the read
      permission  for the file itself and "execute" permission
      for the directory that contains it. So, if user sasha doesn't
      want anybody else to see his files, he can achieve this by
      removing the execute permission on his home directory for all
      other users. This way, no one but himself (and, of course,
      root) will be able to read any of his files, no matter what
      the permissions of individual files are.
    </para>
    <para> Detailed explanation of the permission system can be
      found, for example, in the info page for the GNU "File
      Utilities" package. You can view this info page using GNOME Help
      browser. 
      </para>
  </sect1>

  <sect1 id="syslinks">
    <title>Symbolic links</title>
    <para>
      In addition to regular files, UNIX also has special files
      called <emphasis>symbolic links</emphasis> (or
      <emphasis>symlinks</emphasis> for short). These files do not
      contain any data; instead, they are just "pointers," or
      "shortcuts" to other files. For example, sasha can have a
      symlink named <filename>ft.txt</filename> pointing to the file
      <filename>papers/fieldtheory.txt</filename>; this way, when a
      program tries to access the file <filename>ft.txt</filename>,
      the file <filename>papers/fieldtheory.txt</filename> will be
      opened instead. As you can see from this example, the symlink
      and the target file can have different names and be located in
      different directories.
    </para>
    <para> Note that deleting, moving, or renaming the symlink file
      has no effect on the target file: if sasha tries to delete the
      file <filename>ft.txt</filename>, it is the symlink that will
      be deleted, and the file
      <filename>papers/fieldtheory.txt</filename> will remain
      unchanged.  Also, the permissions of the symlink are
      meaningless: it is the permissions of the target file that
      determine whether a user has the access to it.
    </para>

    <para> Symlinks can also point to directories.  For example, on
      the GNOME FTP server (<systemitem>ftp.gnome.org</systemitem>),
      there is a file <filename>/pub/GNOME/latest</filename>, which at
      the time of this writing is a symlink to directory
      <filename>/pub/GNOME/gnome-1.0.53</filename>. By the time you
      read this, the latest version of GNOME is likely to change, and
      the GNOME maintainers will change the symlink correspondingly,
      so that it will point to
      <filename>/pub/GNOME/gnome-1.2</filename> or something similar.
    </para>
  </sect1>
  <sect1 id="new-mount">
    <title>Mounting and unmounting drives</title>
    <para>
      As we mentioned earlier, the directories on a UNIX system are
      organized in a tree, with the top level directory being
      <filename>/</filename>. Unlike some other operating systems such as
      MS-DOS, there are no special names for files on your floppy disk or
      CD-ROM: <emphasis>all</emphasis> the files accessible to your system
      must appear in the main directory tree starting with
      <filename>/</filename>.
    </para>
    <para>
      Thus, before you can access files on a floppy diskette or a
      CD-ROM, you must give to your system a command to incorporate
      the contents of this diskette into the main directory tree,
      which is referred to as <emphasis>mounting</emphasis> the
      diskette. Typically the contents of the CD-ROM will appear under
      the name <filename>/mnt/cdrom</filename>; the floppy diskette
      under <filename>/mnt/floppy</filename> (these are called the
      <emphasis>mount points</emphasis> and are defined in the special
      configuration file, <filename>/etc/fstab</filename>). Accessing
      a drive in this fashion doesn't mean that the system will copy
      all the files from the CD to the directory
      <filename>/mnt/cdrom</filename>. Instead, it means that the
      directory <filename>/mnt/cdrom</filename>
      <emphasis>represents</emphasis> the CD-ROM: When a program tries
      to access, say, a file called
      <filename>/mnt/cdrom/index.html</filename>, the system will look
      for file <filename>index.html</filename> on the CD-ROM.
    </para>
    <para>
      So, in short: before you can use files on a drive, you must
      "mount" it. Similarly, <emphasis>before removing the disk from
      the drive, you must unmount it.</emphasis>
    </para>
    <para>
      When using GNOME, you usually do not have to worry about
      mounting and unmounting: GNOME scans the appropriate
      configuration file and places the icons for all drives on your
      desktop. Double-clicking on any of these icons automatically
      mounts the corresponding drive (if it was not already mounted)
      and starts the file manager in the appropriate directory.
      Similarly, if you right-click on the drive icon and choose the
      command <guimenuitem>Unmount Volume</guimenuitem> from the pop-up
      menu, GNOME automatically unmounts it before ejecting. You can
      also mount a drive by right-clicking on the desktop and choosing 
      <guimenuitem>Disks | cdrom</guimenuitem> from the pop-up menu,
      or by using the disk mount applet.
    </para>
    <para>
      Note that you can't unmount a drive if it is being used by some program;
      for example, if you have a terminal windows open in a directory on the
      drive you're trying to unmount. So, if you get the error message "Device
      busy" while trying to unmount a drive, make sure that none of your open
      applications is accessing a file or directory on this drive.
    </para>
    <para>
      However, GNOME cannot prevent you from ejecting the disk using the
      physical eject button on the drive itself &mdash; in this case,
      <emphasis>it is your responsibility to unmount the drive</emphasis>
      before doing so. For CD and Zip drives, the system blocks the eject
      button on the drive while the drive is mounted; for floppy drives this
      is technically impossible.
    </para>

    <important>
      <title>IMPORTANT</title>
      <para>
	If you eject a floppy  disk using the eject button on the drive without
	first unmounting it, you may lose your data!
      </para>
    </important>

    <para> Some systems are running a special program, called the
      automount <emphasis>daemon</emphasis> (you do not need to know
      what a daemon is),
      which automatically mounts a drive when a disk is inserted and unmounts a
      drive if it hasn't been used for a specified period of time. In
      this case, you will probably never need to worry about
      mounting/unmounting drives yourself. 
    </para>
    <para>
      Allowing users to mount and unmount drives carries some security risks,
      so many systems are configured so that only root can mount or unmount
      drives. This is the most probable cause of error messages while trying
      to mount a drive. In this case, discuss this matter with your system
      administrator. 
    </para>
    <para>
      If the computer is your personal workstation or home computer,
      so that you are not worried about security, you can give mount
      permission to ordinary users. The easiest way to allow this is
      to use the application
      <application><emphasis>linuxconf</emphasis></application> (which
      can only be run by root).  Just select the drive you want to
      access in the <guilabel>Access local drive</guilabel> section.
      In the <guilabel>Options</guilabel> tab select the
      <guilabel>User Mountable</guilabel> option.  Your drive will now
      be mountable by users.
    </para>
    <para>
      If <application><emphasis>linuxconf</emphasis></application> is not
      available, then you must manually edit the file 
      <filename>/etc/fstab</filename> to include user access. This is done
      by adding the "user" attribute to the drive. For example:
    </para>
    <para>
      If your fstab file contains a line like this:
    </para>
      <programlisting>
/dev/cdrom /mnt/cdrom iso9660 exec,dev,ro,noauto 0 0
      </programlisting>
      <para>
      add the word "user" to the fourth column:
    </para>
    <programlisting>
/dev/cdrom /mnt/cdrom iso9660 user,exec,dev,ro,noauto 0 0
    </programlisting>
  </sect1>

  <sect1 id="devices">
    <title>Drives and devices</title>
    <para>
      Under UNIX, the word "device" is used for all peripheral
      devices connnected to your computer; this includes hard drives,
      floppy and CD-ROM drives, audio and video cards, serial and
      parallel ports, and much more. Each device has a name, such as
      <filename>/dev/hda</filename>. The most common device names are
      listed below.
    </para>
    <itemizedlist>
      <listitem><para>
	  <filename>/dev/hd*</filename> (where *=a,b,c, &hellip;):
	  these are IDE devices, such as hard drives, CD-ROM drives
	  and ZIP drives. <filename>/dev/hda</filename> denotes the
	  master drive on the first IDE controller (usually your first
	  hard drive, <filename>C:</filename> under Windows),
	  <filename>/dev/hdb</filename> is the slave drive on the fist
	  controller (this can be a second hard drive or a CD-ROM),
	  and so on. See also the <link linkend="zippartition">note</link> below
	  about ZIP drives. 
	</para></listitem>

      <listitem><para>
	  <filename>/dev/sd*</filename> (where *=a,b,c, &hellip;):
	  these are SCSI devices, usually hard drives. 
	</para></listitem>
    </itemizedlist>

    <note>
      <title>NOTE</title> 
      <para>If the acronyms IDE and SCSI are new to you, here is a
      brief explanation: there are two types of interfaces for hard
      drives and other similar devices: IDE (and its cousins such as
      EIDE, ATAPI, etc.) and SCSI. SCSI provides better performance,
      but is more expensive, so it is only used on
      servers. If you are not sure what kind of drives you have, most
      probably it is IDE. </para>
    </note> 
    <itemizedlist>
      <listitem><para>
	  <filename>/dev/fd*</filename> (where *=0,1, etc) are floppy
	  drives; <filename>/dev/fd0</filename> is the first drive (it
	  corresponds to <filename>A:</filename> under Windows),
	  <filename>/dev/fd1</filename> is the second
	  (<filename>B:</filename>), etc. 
	</para>
      </listitem>
      <listitem><para>
	  <filename>/dev/lp*</filename> (where *=0,1, etc) are
	  parallel ports; most commonly, these ports are used to
	  connect a printer to the
	  computer. <filename>/dev/lp0</filename> corresponds to
	  <filename>LPT1</filename> under Windows,
	  <filename>/dev/lp1</filename> to <filename>LPT2</filename>,
	  etc.  
	</para>
      </listitem>
      <listitem><para> <filename>/dev/ttyS*</filename> (where *=0,1,
	  etc) are serial ports; these ports are commonly used for
	  connnecting a mouse or a
	  modem. <filename>/dev/ttyS0</filename> corresponds to
	  <filename>COM1</filename> under Windows,
	  <filename>/dev/ttyS1</filename> to <filename>COM2</filename>,
	  etc.
	</para>
      </listitem>
      <listitem><para> 
	  <filename>/dev/audio</filename> and
	  <filename>/dev/dsp</filename> &mdash; these two device
	  names are used for your audio card (they are not equivalent,
	  since they are used for different types of audio files). 
	</para>
	</listitem>
    </itemizedlist>
    <para>
      In addition, it is a common practice to have symlinks
      <filename>/dev/floppy, /dev/modem</filename> and
      <filename>/dev/cdrom</filename> pointing to the actual device
      name corresponding to your floppy drive, modem, and CD-ROM drive
      respectively.
    </para>
    <para>
      You rarely need to use these device names. In particular, if you
      want to access a file on a drive, you do not use the device name
      (such as <filename>/dev/fd0</filename>); instead, you first
      mount the device so that its contents shows as a subdirectory
      (for example, <filename>/mnt/floppy</filename>) in the main
      directory tree, and then use this directory for accessing
      files; see <xref linkend="new-mount"> for more information. About
      the only time when you actually need to use the device names is
      when you are configuring some newly installed program. For
      example, a fax program can ask you for the device name for your
      modem (in which case you can either give it the actual device
      name, such as <filename>/dev/ttyS1</filename>, or just use the
      symlink <filename>/dev/modem</filename>).
    </para>
    <para> And just for fun: there is also a device
    <filename>/dev/null</filename> which acts as a "black hole": you
    can send to it any information, and it never returns. So if you do
    not want to be bothered by error messages, re-direct them to
    <filename>/dev/null</filename> -:). 
    </para>

    <sect2 id="partitions">
      <title>Partitions</title>
      <para>
	Note that it is possible to subdivide a hard
	drive (or a similar device) into parts which for all practical
	purposes behave as independent disks, even though physically
	they reside on the same disk. These parts are called
	"partitions" (under Windows, the name "logical disk" is
	used). For example, you can partition your hard drive into
	several partitions, and install different operating systems in
	different partitions; you can reformat each partition
	independently of the others. This partitioning of the hard
	drive is usually done during the installation of the operating
	system; refer to your installation guide for more
	information. 
      </para>
      <para> 
	If your hard drive has been partitioned, then each partition
	is considered as a separate device. For example, if your hard
	drive is <filename>/dev/hda</filename>, then the first
	partition on this drive would be referrred to as
	<filename>/dev/hda1</filename>, the second as
	<filename>/dev/hda2</filename>, and so on. 
      </para>
      <warning id="zippartition">
	<title> Partitioning of ZIP disks</title> 

	<para> For reasons unknown to us, the pre-formatted
	  ZIP disks sold in stores or formatted using Iomega's ZIP
	  tools under Windows are partitioned in a strange way:
	  they have only one parition (of Windows type, of course),
	  but this partition has number 4. Thus, if your ZIP drive is
	  <filename>/dev/hdc</filename>, the correct device name you
	  should use for such disks is <filename>/dev/hdc4</filename>.
	</para>
      </warning>
    </sect2>
  </sect1>
</appendix>