How to burn an ISO image

Original Document: Ross Laver
CentOS Document: Johnny Hughes

Original Document: e-smith, inc.
CentOS Document: The CentOS Project


1. What is an ISO image?

An ISO is a file that contains the complete image of a disc, from sector 0 to the end. Such files are often used when transferring CD/DVD images over the Internet, and are commonly used as a way of offering Linux distributions for download. The latest versions of CentOS, for example, are available from centos.org as ISO images. Once you have an ISO image on your hard drive, you can burn it onto a CD or DVD using one of many ISO-burning software packages.

More precisely, an ISO image is an image of an ISO 9660 CD-ROM or DVD-ROM. ISO is short for the International Organization for Standardization. (ISO is not an acronym. Instead, the name derives from the Greek word iso, which means equal.) The ISO 9660 format defines the file system used by almost all CDROMs or DVDROMs for Windows, Mac, Linux and so on.

Some ISO-burning applications create plain ISO 9660 images, while others interpret the ISO format as they like. Nero, from Ahead Software, uses the NRG suffix to name its ISO images. ISO images created by Easy CD Creator (from Roxio, Inc., which was spun off from Adaptec, Inc. in September, 2000) contain some lead-in and lead-out bytes around the core of the 2048-byte sector. This explains why ISO images created by Easy CD Creator cannot be burnt by all burning packages (for example, CDRWin complains about the file not being a multiple of the sector size). On the other hand, Easy CD Creator can burn plain ISO images written by other packages.


2. Important notes

To create a bootable CD or DVD from an ISO image, you must burn the actual ISO image onto the CD / DVD, not just copy the ISO file to the CD / DVD. For software not covered below, look for a Burn Image option to accomplish this.

Warning: Just copying the ISO file to the CD / DVD will not produce a usable disc.

Take care to download ISO images in binary mode if using FTP. By default, Netscape downloads the file in ASCII mode, which corrupts the image.

Do not operate any other programs while the CD / DVD is being written to.

Do not bump or nudge the CD / DVD burner while it is operating. Vibrations can cause the burning process to fail.

If you don't have a CD /DVD burner, find a Linux user group near you. Someone will be sure to help.

If you would rather purchase pre-made CentOS CD / DVDs, please see our Official CentOS CD / DVD Vendors


3. Using md5sum (or sha1sum) to verify the integrity of your ISO image

Before you burn your CD, it's a good idea to check the integrity of the CentOS ISO image you downloaded. You can do this quickly using md5sum or sha1sum. When you perform an md5sum (or sha1sum) check, you are comparing the unique "signature" of the file you downloaded to the signature of the file on the server you downloaded from. If the md5 (or sha1) signatures match, you have an uncorrupted file.

To perform an md5sum (or sha1) check on your downloaded file, you need two things. The first is the md5sum (or sha1sum) program, which is included in all major Linux distributions. A free version of each is also available for Windows, md5sum.exe and sha1sum.exe are available from the CentOS dostools directory (see below for instructions).

The second thing you need is the unique md5sum (or sha1sum) signature of the original file on the server from which you downloaded. This can be found in the same directory as the iso image, in the file called md5sum.txt or sha1sum.txt.


3.1. Checking the md5sum (or sha1sum) under Linux

  1. Make sure you are in the directory in which you saved the downloaded iso image.

  2. At a command prompt, enter the command (where filename is the name of the iso file):

    
 md5sum filename
    

    or

    
 sha1sum filename
    
    The calculation may take several minutes. When it's done, you should see the md5 (or sha1) signature (a 32-digit sequence of numbers and letters) of the iso image you downloaded.

  3. Compare this with the signature of the file on the server. If they are the same, you can be sure that the image on your computer is uncorrupted. If they differ, the image is corrupted and you will have to download it again.


3.2. Checking the md5sum (or sha1sum) under Windows/DOS

  1. Download md5sum.exe or sha1sum.exe from the CentOS dostools directory. If you are using Windows 95/98/Me, you should download to c:\windows\command. If you are using Windows NT/2000/XP/Vista, you should download to c:\winnt\system32 (or c:\windows\system32 ... substitute your actual drive letter for c: if required).

  2. Open an MS-DOS window and change to the directory of the file you want to check.

  3. When you are in that directory, enter the command (where filename is the name of the iso file):

    
 md5sum filename
    

    or

    
 sha1sum filename
    
    The calculation may take several minutes. When it's done, you should see the md5 signature (a 32-digit sequence of numbers and letters) of the iso image you downloaded.

  4. Compare this with the signature of the file on the server. If they are the same, you can be sure that the image on your computer is uncorrupted. If they differ, the image is corrupted and you will have to download it again.


4. How to burn your CD / DVD ISO

The method you use will depend on which CD / DVD writing software package you use. It's a good idea to consult the CD / DVD writing software's documentation before you start, because if you make a mistake you'll probably have to throw the disc out and start again.


4.1. Instructions using Easy Media Creator (Adaptec/Roxio) on Windows

  1. Insert a blank media into the writer.

  2. Start "Creator Classic"

  3. Select "Other Tasks"

  4. Select "Burn from Disc Image File"

  5. Select the ISO image file.

  6. Click on OK.

  7. Click on OK once again to burn the image.


4.2. Instructions using Nero Burning ROM (Ahead Software) On Windows

  1. Insert a blank media into the writer.

  2. Launch Nero.

  3. In the File menu, select "Burn CD image".

  4. Choose as file type: all files (*.*), since Nero expects files with the NRG suffix.

  5. Select the ISO image file.

  6. You will see a dialog box asking if you want to supply detailed image parameters. Enter the following parameters:

    • Type of image: Data Mode 1

    • Block size: 2048 bytes per sector

    • File precursor and image trailer: 0 length

    • No scrambled and no Swapped.

  7. Click on "burn". If the program complains that there are errors in the image file, click on the button "Ignore" and launch the burning.


4.3. Instructions using Nero Express (Ahead Software) On Windows

  1. Insert a blank media into the writer.

  2. Launch Nero Express.

  3. Select "Disc Image or Saved Project"

  4. An Open dialog appears. Select the ISO Image file. Click Open.

  5. The next screen allows you to select Writing Speed. The best setting is based on your actual hardware, but if you have problems, try slower speeds.

  6. Click "Next" to burn.


4.4. Instructions using WinOnCD (CeQuadrat GmbH, now part of Roxio, Inc.) on Windows

You need to create a Track Image project in WinOnCD for the image file. Please note that the program doesn't accept the ISO suffix for the image, and that you'll have to rename it with the raw suffix.


4.5. Instructions using CDRWin (Golden Hawk Technology) on Windows

Open the icon labeled "File Backup and Tools". In the listbox named "Backup/Tool Operation", select "Record an ISO 9660 Image File". In the box "ISO 9660 Image File", click on the button labeled "..." (Browse) and select the ISO image file. At the bottom of the dialog box, select CD-ROM and Mode 1. Then click the button labelled "START".


4.6. Instructions using ISO Recorder V2 Power Toy on Windows

  1. Obtain and install the ISO Recorder power toy from the web site.

  2. Insert a blank media into the writer.

  3. In Windows Explorer, right click on the first ISO image file that you want to burn.

  4. In the context menu, select "Copy image to CD".

  5. Follow the steps given by the "CD Recording Wizard" pop-up.


4.7. Instructions using k3b on CentOS

  1. Insert a blank media into the writer.

  2. Launch k3b (Menu -> Sound & Video -> K3b).

  3. From the "Tools" Menu, Select "Burn CD Image" or "Burn DVD ISO Image" as applicable.

  4. An Open dialog appears. Click on the "Folder Icon", then select the ISO Image file. Click Open.

  5. Click the "Start Button" to burn the image.


4.8. Instructions using cdrecord or growisofs on CentOS

  1. cdrecord example

    cdrecord -v dev=ATA:1,0,0 driveropts=burnfree -dao filename

    Detailed cdrecord information

  2. growisofs example

    growisofs -dvd-compat -Z /dev/hdc=filename

    Detailed growisofs information


5. Links

TLDP CD Writing HowTo (tldp.org)

Andy McFadden's CD-Recordable FAQ (www.cdrfaq.org)

Roxio, Inc. (www.roxio.com)

Ahead Software (www.ahead.de)

CeQuadrat (www.roxio.de)

Golden Hawk Technology (www.goldenhawk.com)

ISO Recorder power toy (isorecorder.alexfeinman.com)


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