ISO image

From openSUSE

How this works

• User downloads ISO image,
• check is download correct using included md5 sums,
• then burn it to empty medium (CD-R, CD-RW, DVD-R, DVD+R, DVD-RW, DVD+RW)
• that creates installation DVD or Live CD, and
• reboot (restart) computer with medium in the optical drive.

Most of today's computers are set to boot from optical drive first, then from the hard disk, so computer will "wake up" using programs written on DVD or CD instead of usual way using similar kind of programs on hard disk.

Format

• As with any other archive, an ISO image includes all the data of files contained on the archived CD/DVD, or any other disc format. They are stored in an uncompressed format. In addition to data of the files it also contains all the file system metadata, including boot code, structures, and attributes. ISO images do not support multi-track, thus they cannot be used for audio CDs, VCD, and hybrid audio CDs, which are usually ripped as audio files. However, for disks that contain a single track of data followed by tracks of audio, such as video game disks, the first track can be ripped as an ISO, and the rest as audio files.

• These properties make it an attractive alternative to physical media for the distribution of software as it is simple to transfer over the Internet or via a LAN connection.

• A valid ISO image is an uncompressed collection of various files merged into one single resulting file, according to definite and standard formatting.

• The most important feature of an ISO image is that it can be easily rendered or "burned" to a DVD or CD by using media "authoring" or disc "burning" software. It can also be opened using archival applications such as 7-Zip file manager or the WinRAR shareware archiver or the Ark(Linux Platform).ISO burning is now typically a native feature of modern home and business computer operating systems.

What to watch

First check so called MD5SUM. It is checksum used to verify that downloaded file has no errors. The MD5SUM file containing md5 sums for all ISO is usually in the same directory as the ISO files. If you already have Linux installed program that will check md5 sum must be part of installation. <TODO- find md5 checker for windows>.

1) First time users, of this method to acquire and install software, have to watch to use proper option in burning software. Usually it is called something like "Burn ISO image".

1.1) Just moving file to the list of files that has to be burned will burn ISO image on disk as a file. That means iso image will be on wrong place on a disk, and it will be impossible to boot from that disk. If that is the case looking in Explorer you will see listed one file ending with .iso instead of many files and folders like this http://download.opensuse.org/distribution/11.0/repo/oss/ .

1.2) Opening iso image file using some viewer program, and then burning all files to the disk will produce disk that is not bootable. While you can see many files as on http://download.opensuse.org/distribution/11.0/repo/oss/ it will miss boot sector, which contains the very first program needed to boot from optical media.

2) Burning speed is usually handled by burning program, but due to differences in manufacturing raw media, automatic selection will sometimes select speed that is too high and DVD or CD will contain errors. If result of burning is CD or DVD that works to some point, it might be this case. Cure is to select manually burning speed. To be sure that this will work use some speed that is close to the half of the maximum.

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