# CDServer-HOWTO

### Randolph J Tata

Talcon Information Systems

randy@talcon.com

v1.40 2002/01/10

Revision History
Revision v1.40 | 2002-01-10 | Revised by: rjt
Added description and link to cdtower shell script.
Revision v1.30 | 2002-01-08 | Revised by: rjt
Many additions and changes to markup in DocBook XML source and fix pubdate data.
Revision v1.01 | 2002-01-07 | Revised by: rjt
Updated for 2.4 kernels. Added more References and links. Convert to DocBook XML 4.1.2 Change License from LDP boilerplate to GFDL.
Revision v1.00 | 2000-09-23 | Revised by: rjt
Conversion from Linuxdoc SGML to DocBook v3.1 SGML
Revision v0.10 | 2000-09-01 | Revised by: rjt
Conversion to Linuxdoc SGML from text/html, added kerneltweak (addloops) section
Revision v0.01 | 2000-08-18 | Revised by: rjt
First version released in text and html.

The CD Server HOWTO describes the steps and commands you can use to setup your own CD Server using Linux and some built-in Unix commands along with other freely available software packages. The CD Server can then share the CD's via the network to Windows and/or other client machines.

# 1. Introduction

With disk space becoming less expensive (100GB Western Digital 7200rpm available for US $195 in January 2002), it is viable to use an Open Source software-based CD Server solution, instead of paying $800-$4,000 for a software, thin-server, or CD Jukebox solution.

I've setup my CD Server on a Pentium 200 with 64MB RAM, using one of these large drives.

Any comments, suggestions, additions, or corrections can be sent to my email address at Talcon Information Systems: `<randy@talcon.com>`.

## 1.1. Intended Audience

This HOWTO is specifically directed toward System Administrators and uses Linux for the examples. It should work with other flavors of Unix provided that they have a loop device or a method of mounting a CD image file within the directory tree as a block device using the iso9660 file system.

## 1.2. Things You'll Need

The commands and utilities needed to setup your own CD Server are already included in most (if not all) Linux distributions.

- A Linux Distribution (This HOWTO uses Linux-Mandrake for the examples)

- dd - Converts and copies a file (a standard Unix command)

- mount - Mounts and Unmounts filesystems (a standard Unix command)

- Samba - A Windows SMB/CIFS fileserver for Unix

- NFS (optional for Unix) - Network File System (included in Linux distributions)

- Netatalk (optional for Macs) - A package that lets a Unix machine supply Appletalk print and file services on a LAN.

Note

  Previous to the 2.4 kernels, the Linux-Mandrake distribution I was using only had support for 8 loop devices compiled into the kernel (see Section 3 to increase this number). At that time, you were only be able to share 8 CD's on a network with that default value, and to share more than 8, the loop block driver source code (loop.c) needed to be modified and a new kernel compiled.

  With the 2.4 kernels, that is no longer required. You can now set the number of loop devices dynamically via the max_loop module parameter, or by passing max_loop=[1-255] to the kernel on boot.

## 1.3. Suggested Reading and References

SMB HOWTO by: David Wood, dwood (at) plugged.net.au. Part of the Linux Documentation Project. This document describes how to use the Server Message Block (SMB) protocol, also called the Session Message Block, NetBIOS or LanManager protocol, with Linux using Samba.

Using Samba by: Robert Eckstein, David Collier-Brown, Peter Kelly 1st Edition November 1999, O'Reilly and Associates, Inc. ISBN 1-56592-449-5,

The Linux CD-ROM HOWTO by: Jeff Tranter, tranter (at) pobox.com. Part of the Linux Documentation Project. How to install, configure, and use CD-ROM drives under Linux. It lists the supported hardware and answers a number of frequently asked questions. This HOWTO also gives some information on using multi-platter CD-ROM drives with Linux.

CD-Writing HOWTO by: Winfried Trümper, winni (at) xpilot.org. Part of the Linux Documentation Project. This document explains how to write CD-ROMs under Linux. This HOWTO also includes information on making 1:1 image copies of CD-ROMs.

## 1.4. Copyright and License

CDServer-HOWTO, Copyright © 2000-2002, by Randolph J. Tata, All Rights Reserved

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in Appendix A entitled "GNU Free Documentation License".

## 1.5. Disclaimer

Use the information in this document at your own risk. I disavow any potential liability for the contents of this document. Use of the concepts, examples, and/or other content of this document is entirely at your own risk.

All copyrights are owned by their owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting the validity of any trademark or service mark.

Naming of particular products or brands should not be seen as endorsements.

You are strongly recommended to make a backup of your system before major installation and should make backups at regular intervals.

## 1.6. News

As always, check the revision history at the top of this document.

DocBook XML source for this document is available. Any additions/changes should be made to the DocBook XML source, not derivative formats.

This documents home page is at the CDServer-HOWTO site page in case you need the latest version, or there is a problem with the page format you are viewing.

## 1.7. Credits

My thanks go the readers of this HOWTO and those willing to share their experiences and knowledge with me. I have the pleasure of acknowledging:

Mark F. Komarinski | markk (at) linuxdoc.org | LDP Author Guide
Jorge Godoy | godoy (at) metalab.unc.edu | LDP Author Guide
David C. Merrill | dcmerrill (at) mindspring.com | LDP Author Guide
Stein Gjoen | sgjoen (at) nyx.net | HOWTO-Template
Gregory Leblanc | gleblanc (at) cu-portland.edu | HOWTO-Template
Greg Ferguson | gferg (at) sgi.com | HOWTO-Template
Amar Chaouche | achaouche (at) linbox.com | mount unhide option
Giblhauser Carl Michael | mike (at) bawb.bmlf.gv.at | runoutblock i/o errors
Monte Milanuk | milanuk (at) yahoo.com | nfs help
Paul A. Sand | pas (at) unh.edu | loop module option max_loop
Tony Melia | Tony.Melia (at) downsmicro.com.au | max_loop kernel boot parameter
Richard Black | Richard.Black (at) compaq.com | more info and mknod script
Bradley Wendelboe | krakken (at) icehouse.2y.net | cdtower shell script
James Mumm | dart (at) windeath.2y.net | cdtower shell script

## 1.8. Translations

- Korean (html and sgml) at http://www.ibiblio.org/pub/Linux/docs/HOWTO/translations/korean/

If you have the capacity it would be nice to make the CDServer-HOWTO available in a number of formats and languages.

If you've translated this document, please send to me:

- Your name, email address, the language and URL to the translated document (preferred).

- Or an email attachment of the work.

Please send either to my email address at Talcon Information Systems: `<randy@talcon.com>`.

# 2. Procedure

Summary of Steps

- Create a large partition to hold the CD Image Files.

- Copy the CD to an image file using the dd command.

- Mount the CD image file within the directory tree.

- Share the directory on the network using Samba, NFS, etc.

Also, make sure you've read Section 1 and Section 1.2.

## 2.1. Creating the ISO Images

Choose (or create) a file system with the largest available disk space on it. Keep in mind that CD-ROM's can hold around 640MB of data, so if you want to share 8 full CD's on your network, you'll need 5.1GB of space available.

Login as root or "su" to root.

    bash# df -h

    Filesystem            Size  Used Avail Use% Mounted on
    /dev/hda5             1.4G   82M  1.3G   6% /
    /dev/hda1              15M  827k   14M   6% /boot
    /dev/hda7             2.4G 1008M  1.3G  43% /usr
    /dev/hda8            23.6G 11.7G 11.7G  50% /home

Here the `/home` filesystem has the most available space, so it is the most suitable filesystem to use for dumping the CD images to.

    bash# cd /home
    bash# mkdir image
    bash# cd image

Now, copy the CD to an ISO image. You must know the device name of your CD-ROM drive (usually `/dev/cdrom`, it could be `/dev/scd0` for SCSI CD-ROM's) I'll use the Mandrake distribution CD-ROM as an Example:

    bash# dd if=/dev/cdrom of=mndrk81.iso

Note

  The "if=" is the input file, the "of=" is the output file. You should see a message stating the number of records in and number of records out.

  If you see i/o errors, they will most likely be due to the lead-in and lead-out runoutblocks on the CD. If the number of records in and number of records out do not match you may have a problem, otherwise the image will most likely be alright, but you can never know if the errors happened while reading the ISO part of the CD or not (due to dust or scratches on the CD).

  Other utilities to read CD's exist, like readcd or sdd.

  More information about making 1:1 copies of CD's exists in the [CD-Writing-HOWTO], see Section 1.3.

My thanks to Giblhauser Carl Michael for the runoutblock information.

## 2.2. Mounting the ISO Images

The next step is to mount the ISO image file. Let's create a directory under `/mnt` to place the mounted file.

    bash# cd /mnt
    bash# mkdir iso
    bash# cd iso
    bash# mkdir mndrk81

Now mount the ISO image file to this newly created directory

    bash# mount -o loop,unhide -t iso9660 -r /home/image/mndrk81.iso /mnt/iso/mndrk81

Note

  The "-o loop" means use the option that mounts a file as a block device. The unhide option shows hidden files. The "-t iso9660" means that the file is in the iso9660 CD-ROM format. The "-r" means to mount read-only.

Thanks to Amar Chaouche for pointing out the unhide option for the mount command.

Now you can:

    bash# cd mndrk81
    bash# ls -al

You should see a listing (ls) of the files and directories that are on the actual CD (only now they're inside the ISO image file, and that's what you're currently looking at!)

## 2.3. Mounting the Image upon System Restart

Now that we've manually mounted the image, and made sure it works, an entry needs to made in the `/etc/fstab` file so that the image is remounted on the next system startup. It's important to make the entry AFTER the entry for the parent filesystem, e.g. `/home` (I use vim, but emacs, joe, pico or jed will work just as well):

    bash# vim /etc/fstab

After the line that looks like the following (or whichever filesystem you've placed your images):

    /dev/hda8 /home ext2 defaults 1 2

Insert the following line with your text editor:

    /home/image/mndrk81.iso /mnt/iso/mndrk81 iso9660 ro,loop,auto,unhide 0 0

## 2.4. Sharing it on a Windows Network using Samba

You'll need to have Samba installed and working to perform the next steps (that's outside the scope of this instruction, see Section 1.3). If it's not yet installed, consult your Linux distribution's instructions for installing the Samba package. Or you can visit the Samba website at http://us1.samba.org/samba/samba.html for installation instructions, binaries, and/or the source code.

To share your mounted CD's on a windows network, simply create a stanza in the `/etc/smb.conf` file similar to the following:

    [cdimages]
      comment = All Shared CD Images
      path = /mnt/iso
      public = yes
      writable = no

This will share all the subdirectories under the `/mnt/iso` directory on the network. To mount the share to a local drive (in this case the I: drive), bring up an MS-DOS Prompt on the Windows machine and type the following:

    C:\> net use I: \\yourlinuxmachine\cdimages

Each CD image will now appear as a subdirectory on the I: drive of your Windows machine.

To mount ONLY the Mandrake CD image to a drive letter (we'll use M:, the root drive of which, will correspond exactly to the CD as if it was just inserted in the CD-ROM drive), create the following stanza in the `/etc/smb.conf` file.

    [mndrk81]
      comment = Mandrake Linux 8.1
      path = /mnt/iso/mndrk81
      public = yes
      writable = no

Then, at your MS-DOS Prompt, mount it with the following command:

    C:\> net use m: \\yourlinuxmachine\mndrk81

Warning

  The Samba smb.conf file stanzas presented here are simplified, and not secure. Many more options exist for a Samba share which limit who can mount the shares, control how user authentication is performed, and whether the share is even browseable through Network Neighborhood on the Windows machines.

## 2.5. Sharing the Images on a Unix network using NFS

Make sure that NFS is running and configured correctly on your Linux machine, then add the following to the `/etc/exports` file using your own preferred options:

    # sample /etc/exports file
           /mnt/iso            (ro,insecure,nohide,all_squash)

Note

  The nohide option will allow you to mount a parent directory, without explicitly mounting all exported subdirectories beneath it.

Now try running:

    bash# exportfs -r

This should re-export everything in your `/etc/exports` file.

Now, when typing "showmount -e `yourlinuxmachine`" you should see that the `/mnt/iso` directory is included in the exports list.

# 3. Adding Support for More Loop Devices

Newer Linux kernels (2.4) allow you to add more loop devices easily by editing `/etc/modules.conf` or through the use of a boot parameter.

Older kernels (2.2 ?) only had support for 8 loop devices compiled into the kernel. In short, you were only able to share 8 CD's on a network with this default value. In order to support more than that default, you needed to modify the kernel source and recompile a new kernel.

Use the following methods to determine which version of the kernel you are running.

    bash# uname -a

or

    bash# cat /proc/version

## 3.1. Adding the Loop Module Option

Current kernels allow you to set the number of loop devices supported without recompiling the kernel. One of these methods is to add an options line to `/etc/modules.conf`. This method will only work if your loop support has been configured as a loadable kernel module (which is how most major Linux distributions come preconfigured now).

Edit `/etc/modules.conf` and add the following line.

    options loop max_loop=64

After making the above change, simply reboot. Or you can try to use rmmod and insmod to make the change on the fly - but this will not work if you currently have any loop devices mounted (you'll get an error saying loop: Device or resource busy).

Note

  If you do not have an `/etc/modules.conf` file, your module configuration file may be called `/etc/conf.modules` (this name is now deprecated).

Continue with Section 3.4.

Thanks to Paul A. Sand for pointing out the /etc/modules.conf option.

## 3.2. Appending to the Boot Prompt

If your loop support has been compiled directly into the kernel (in other words, it is not loaded as a module), you can append the number of loop devices you would like to support at the linux boot prompt.

    boot:  linux max_loop=64

Or, if you are using LILO, you can edit your linux boot stanza in `/etc/lilo.conf` and add/modify the `append=` line. Here is an example stanza showing `append=` (note: only add or modify the append line, don't change your whole stanza to look like this one or your system may not boot). For more information about LILO, consult the LILO mini-HOWTO at http://www.linuxdoc.org/HOWTO/mini/LILO.html.

    image=/boot/vmlinuz
            label=linux
            root=/dev/hdb5
            initrd=/boot/initrd.img

    	append=" max_loop=64"

            vga=788
            read-only

After changing `/etc/lilo.conf`, you need to run the lilo command for your changes to take effect.

    bash# lilo

    Added linux *
    Added linux-nonfb
    Added failsafe
    Added windows
    Added floppy

Next restart your system. After your system restarts, you can check your boot command line by typing the following:

    bash# cat /proc/cmdline

Note

  I am not sure if the loop module (compiled as a module) reads `/proc/cmdline` when the module is loaded, and therefore may not need an options line `/etc/modules.conf`. It's possible that it can (and if it doesn't, it should). To summarize: I have not tested this.

Continue with Section 3.4.

Thanks to Tony Melia for the boot prompt info.

## 3.3. Tweaking the Kernel

If you have an older kernel (v. 2.2) or if you are completely comfortable recompiling the kernel, you can increase the number of loop devices supported by editing the `/usr/src/linux/drivers/block/loop.c` file.

Note

  If you find that the kernel sources are not installed on your machine, you'll need to consult your Linux Distribution's documentation on how to install them (the Kernel Sources come with all distributions - it's part of the GNU GPL licensing).

Change the number in the following line to however many loop devices you'll need.

    #define MAX_LOOP 16

Compile the new kernel or module as the case may be. If you need some help getting started with this, read `/usr/src/linux/README` or consult The Linux Kernel HOWTO.

Continue with Section 3.4.

## 3.4. Creating the Loop Devices in /dev

You should check how many `/dev` entries you have for loop devices.

    bash# ls -l /dev/loop*

The mknod command creates the devices in the `/dev` directory. The loop devices have a major number of "7", and the minor numbers begin at "0". If your `MAX_LOOP` was defined as "8" in `/usr/src/linux/drivers/block/loop.c`, you should have `/dev/loop0` through `/dev/loop7`. To create the `/dev/loop8` device, use the following command (subsitute the appropriate number you need for both the "8's" in the example below).

    bash# mknod -m660 /dev/loop8 b 7 8

Check Owner/Group & Permissions on the new file (using ls -l). You can change the owner and group with the following command:

    bash# chown root.disk /dev/loop8

You can change the permissions using the following command:

    bash# chmod 666 /dev/loop8

# 4. More Information

Be sure to check the suggested reading in Section 1.3.

## 4.1. Frequently Asked Questions

I finally had to create this section - Frequently Asked Questions. Although, I sometimes think it should be called Frequently Answered Questions (at least I try to answer them all).

Q: Can I copy CD contents to a directory and share it with SAMBA?
Q: Do any scripts or programs exist that automate this process?
Q: Do any web interfaces exist that automate this process?
Q: Can copy-protected CD's (e.g. laserlok) be shared in this way?

Q: Can I copy CD contents to a directory and share it with SAMBA?

A: In a word - Yes.

> There is nothing to keep you from doing that. However I'm not sure which arguments you would have to use with tar and which options to include in the SAMBA stanzas. Also, there could be problems with file name mangling (case sensitivity, spaces in file names), file attributes (read-only), etc. If anyone is doing this successfully, please send me examples of the commands you used for copying the contents of the CD, and your SAMBA stanzas for the shares.

> Here's some commands you can use to copy the contents:

>     bash# cd /home
>     bash# mkdir image
>     bash# cd image
>     bash# mkdir mndrk81
>     bash# mount /mnt/cdrom
>     bash# cd /mnt/cdrom
>     bash# tar cvf - . | (cd /home/image/mndrk81; tar xvf -)

> Thanks to Giblhauser Carl Michael for this info

Q: Do any scripts or programs exist that automate this process?

A: Yes:

- Bradley Wendelboe and James Mumm wrote a shell script called CDTower - see Section 4.2.2 to download it.

  I have no independent test results of this script - use at your own risk.

Q: Do any web interfaces exist that automate this process?

A: Not yet. However there is much interest in this.

- Tony Melia [Tony.Melia (at) downsmicro.com.au] has announced that he is 60% complete with a web interface, i.e. sucking CD's in, creating extra `/dev/loop` entries and seeing what space the CD's are taking up.

- I am planning on writing a module for Webmin to automate this process. That project is currently hosted on SourceForge at http://sourceforge.net/projects/opencdserver

Q: Can copy-protected CD's (e.g. laserlok) be shared in this way?

A: To the best of my knowledge, No.

> Others have reported problems to me trying to share ISO images made from copy-protected CD's. It seems that even when using the "unhide" option with mount that files will remain hidden.

## 4.2. Other Instructions Available on the Web

This section is devoted to instructional materials that others have written or have sent to me.

### 4.2.1. Saving a CD-ROM to a File and Mounting it

Richard Black (Compaq) has some good pages about Saving CD-ROM's to files and mounting them in Red Hat Linux.

- Saving a CD-ROM to a File and Mounting it

- Linux Loop Devices - This page also includes the script below for creating many loop device nodes at once in `/dev`.

    Device nodes are required to access the loop devices. You already have loop0 - loop7.
    You can run the following loop to create the rest of the nodes (loop8 - loop255).
    You can type all of the following lines of code on one single line if you leave off
    the trailing "\" characters.

    C=8; echo; echo "Creating loop device nodes."; \
       while [ $C -lt 256 ]; do mknod /dev/loop$C b 7 $C; \
       echo -n .; C=`expr $C + 1`; done; echo;

    Note: the quoting around the expr section are called backtick's and they are located
    with the tilde character ("~") in the upper left hand corner of the keyboard. The
    character is not a single quote.

Thanks to Richard Black for permission to add this info and for linking back to this document.

### 4.2.2. CDTower v.06

A script to automate the creation of ISO images and share them via Samba

by Bradley Wendelboe [krakken (at) icehouse.2y.net] and James Mumm [dart (at) windeath.2y.net]

This software is covered under the GPL See http://www.gnu.org/copyleft/gpl.html for details.

To view/download this script:

  http://www.talcon.com/projects/CDServer-HOWTO/scripts/cdtower_v0.06.sh.txt

Caution

  I have no independent test results of this script - use at your own risk.

Thanks to Bradley Wendelboe for forwarding this script to me.

## 4.3. Under Future Consideration

These are things I'm currently looking into, trying to figure out, or planning to get done.

- Make more scripts available that others have sent to me, either within this howto, or by hosting them and linking to them from this document.

- Sharing CD's to Apple and Netware clients (Appletalk and IPX).

- Compressed ISO Images.

- Changing CD Shares on the fly (hopefully transparent to users).

- Adding a module to Webmin to automate the CDServer process.

- Distribution specific instructions.

- I have a volunteer for a German translation, hopefully it will be done soon.

# A. GNU Free Documentation License

Version 1.1, March 2000

> Copyright (C) 2000 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

# 0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other written document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

# 1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you".

A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.

A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

# 2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

# 3. COPYING IN QUANTITY

If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

# 4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).

3. State on the Title page the name of the publisher of the Modified Version, as the publisher.

4. Preserve all the copyright notices of the Document.

5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.

8. Include an unaltered copy of this License.

9. Preserve the section entitled "History", and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

11. In any section entitled "Acknowledgements" or "Dedications", preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

13. Delete any section entitled "Endorsements". Such a section may not be included in the Modified Version.

14. Do not retitle any existing section as "Endorsements" or to conflict in title with any Invariant Section.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

You may add a section entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

# 5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections entitled "History" in the various original documents, forming one section entitled "History"; likewise combine any sections entitled "Acknowledgements", and any sections entitled "Dedications". You must delete all sections entitled "Endorsements."

# 6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

# 7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an "aggregate", and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

# 8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

# 9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

# 10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

# How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

> Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. A copy of the license is included in the section entitled "GNU Free Documentation License".

If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.