Well, well, Arnulf
I am happy to say thank you to you and iamystic
for giving me this opportunity, and solving my actual problem as well, as I have thought quite a while about what would be an appropriate contribution for my 500ths post in this forum. And I think helping a fellow lagooner is
an adequate contribution. Therefore: here it is!On CDs, DVDs and ISO images
In case you just need a quick solution, jump directly to chapter 3.1. What it is
Files ending in [font=Courier New].iso
[/font] or [font=Courier New].cdr
[/font] or [font=Courier New].img
[/font] usually denote a certain data format suitable for data CD-ROMs, as standardized by the International Organization for Standardization (ISO) under the number 9660. It is usually referred to as ISO-9660 or ECMA-119. Some popular extensions of this format are known under the name Joliet, Rock Ridge, UDF, and El Torito (for bootable CDs). I only speak about data CDs here, as e.g. audio CDs have a very different file format.
Usually data storage memory as e.g. hard disk, CD-ROM, DVD-ROM, (Backup) Tapes allows the storage of bit patterns of any kind. For applications to be able to read what another application has written onto a specific storage device, it is helpful to organize the data on this storage device in a certain form that is publicly documented and that most applications adhere to. This is called a standard.
Our data is usually organized in chunks that we call "files", and these files are organized in folders which can contain other folders as well, and folders and files are all together stored into one big data structure that we call "The file system". File systems can be categorized by their purpose: there are disk file systems, network file systems, and file systems for special purposes. Some popular examples for disk file systems:
[*]On Windows operating systems, today we usually use the NTFS file system, in older days we also had the FAT file system.
[*]Mac users know the HFS and the HFS+ file system,
[*]Unix users know a huge bunch of file systems like BSD, SysV, ext2, ext3, xfs, Reiser, ...2. How to create it
If you want to store files and folders from (the harddisk of) your computer onto a CD-ROM or a DVD-ROM, you have to organize these files and folders in a different way than it is stored in your file system on your disk. The most popular file format that is suitable for CD burning is what we call in a short form the "ISO" file system. If you use any CD burning software, it usually performs the following steps:
It allows you to collect the files and folders from your computer that you want to burn on your CD.
It compiles them together according to the ISO-9660 file system standard (usually plus some extensions) and produces one single temporary file which is structured internally according to ISO and contains all the files and folders that should be burned on your CD-ROM. This temporary file is often called an ISO image file.
It asks you to insert a blank disk into your CD-R/W device and burns the image file onto your CD.
Depending on your CD burning software, some programs allow you to just stop after step 2, or they burn the whole CD and forget to delete the image file created in step 2. Then you have to do some search on your computer to find it, if you want to have the image file.
In reverse order, if you "read" the content of a data CD, usually the device driver of your operating system is capable of understanding the ISO file format on your CD and extracts individual files form your CD. There is also the possibility to read the CD as a whole and produce one single file which contains the ISO file format. On Windows you need special software for that; some burning software offers this capability. In Linux, it is very simple, just type in a command like
[font=Courier New]# dd if= of=/tmp/myCD.iso[/font]
and that's all.
Now you can also understand, what happens, if you just burn an iso image file like an ordinary file: Your burning software takes this image file into step 1., wraps it into another image file in step 2 and then burns the CD. Then, if you read this CD, the device driver of your operating system unpacks the file on the CD, and you get back your ISO image file, but not the files and folders that are already packed inside.
3. What to do if I have an iso image file?
If you have got an iso image file and you want to access the files and folders inside it, there are basically 2 possibilities to achieve this.
1. Burn a CD
Some CD burning programs, such as Nero (and there are others as well) allow you to burn an image directly to a file or in other words: they allow you to start at Step 3 above. Search through all your options and menues, you might find a place where it offers this possibility. On windows systems, this is the easiest way to access the content of an image file, and a very cheap one, as a CD-ROM only costs a couple of cents nowadays.
2. Read the content of the ISO image without burning a CD
In case your CD burning software does not allow this, or you want to access the content of an iso image directly without burning, you need to do a bit more.
[*]On Linux systems, you can just mount this image with a commmand line like [font=Courier New]# mount imagefile.iso /mnt/iso/ -t iso9660 -o ro,loop=/dev/loop0[/font] and then you find the content of your image file on [font=Courier New]/mnt/iso/...[/font]
[*]On windows you need some special software to do this. On possibility is to use the freely available Software daemon lite. Here is a short summary on how to mount an iso image file in seven [no]days[/no] steps.
1. Download the daemon software from http://www.disc-soft.com/download/daemon/free
2. Start the exe file, accept the license, install it, and reboot your system (hey, it's Windows )
3. Continue the installation (accept the license a second time). During this installation phase you will get a window with options to choose. You only need to select the last option on the bottom of the window "Startmenüverknüpfungen", deselect the others. On the next page, deselect the option "Startseite des Browsers".
4. Then "Installieren" and "Fertigstellen" (Complete installation).
5. After the installation is completed, the scrïpt usually starts your browser with the starting page of the software company: close the browser, it is not important.
6. Now the installation is completed, the application starts. Click on the icon "Virtuelle Laufwerke" and choose from the menu "Laufwerk 0" -> "Image einbinden". Now browse to your image file. To see all files, change the option to "*.*".
7. After pressing "OK" you should see you image file as an additional drive with a separate drive letter, as if you would have just installed a new CD-ROM drive into your computer and have inserted a CD with the corresponding iso image on it.
That's it, basically. And if after reading this post you still have more detailed technical questions, you can regard yourself as a technical expert now and start your own expedition through studying the ISO 9660 standard on your own.
And as there are also numerous other ways to get around this problem, most probably some fellow lagooners would add a descrïption of their most favorite way to deal with an iso image file.