What is meant by an ISO image of a Operating System? How can I make an ISO of an OS? When would you use ISO images of an OS?


Most of the time, People often say ISO when referring to installation disk (images) of of either Officially released Microsoft or Linux Operating Systems. (The other times, it usually refers to a pirate version of any software available on disk).

For example, what a ZIP file is to a folder/files, an ISO file is to CD... an ISO file maintains all files and folders along with the entire disk structure (to a limit) and a few other bits of information.

This makes it the best way to transfer a CD across the internet. For Example, on Technet or MSDN (both require membership), Microsoft give their Operating Systems (and many other pieces of software) away as ISO disk images. After downloading, using a third party tool such as CDBurnerXP (or native now in Windows 7), you simply point the ISO file to a real disk, and it will burn.

Alternatively, you can mount an ISO file to a Virtual Drive using a tool such as Virtual Clone Drive or extract files from it using 7-Zip or Winrar.

If you have any CD file burning software installed, you may want to take a look as some allow you to create an ISO file during the last step where you would target an optical drive.

  • i just downloaded CDBurnerXP, didn't work. Note: CDBurnerXP (despite its confusing name) does NOT work natively in XP, it requires to install dotnet framework. thanks, but no thanks. :) – Molly7244 Dec 6 '09 at 19:14
  • Download the older version from their site - it doesn't require the .net framework... but many many people do have it - but it does work on xp!... – William Hilsum Dec 6 '09 at 19:27
  • will check that ... and i'm sure it does work (IF .net is present). – Molly7244 Dec 6 '09 at 19:33

Wikipedia has a good definition. The short answer is an ISO is a way to send a CD or DVD as a single file that can then be burnt to a disk as a complete file system. The most common use of an OS ISO is to distribute a Linux OS.

  1. What do we mean by ISO image of a Operating system?

    (If we're only concerned with their uses for operating systems,) an ISO image is a binary file representing the entire filesystem of one of the following:

    1. Install CD: These are not capable of running an OS, only installing it.
    2. Live CD: You can run an OS from these, or install the OS (generally)
  2. How do we make a ISO of any OS?

  3. When do we use ISO image of OS?

    • When you want to download an install CD or a live CD from the internet and burn it to a CD yourself.
    • When you want to distribute your own custom CD over the internet

So short answer: Downloading an ISO is the digital way of picking up a CD.

  • Besides install CD and Live CD, you can have an ISO of a fully installed OS. – jiggunjer Dec 31 '15 at 3:38

The term "ISO" refers to the International Organization for Standardization. (The natural abbreviation in English would be IOS, but other languages were apparently influential.) Specifically, ISO is an organization that creates many specifications, which are often called standards. One of these specifications was "ISO 9660", which described how data is stored on a disc like a "CD-ROM". Later, some DVDs were written using the ISO 9660 standard.

Shorter filenames can be nicer to work with. In particular, MS-DOS which was the most popular/dominant operating system around 1993-1994 as CDs started to become popular, and MS-DOS limited file extensions to being no longer than 3 characters. So instead of a fuller extension like “.iso9660”, people typically used the extension of “.iso”. Unsurprisingly, people started to call these files “ISO files” (just as files with a “.zip” extension are often called “ZIP files”).

For optical discs (CDs, and later DVDs), people would frequently use a CD-ROM that they created. This can be true when an organization is using Microsoft's Volume Licensing, but is especially common when using an "open source" operating system. The typical way that people would create such CDs is to download a "CD image", using a file in the "ISO 9660" file format (which is typically a file that ends with “.iso”), and then use some software to “burn” a CD, which is vernacular that just refers to writing to a CD. (Commercially pressed CDs were created by a process that actually burned small holes, or at least "pits", into a layer of the disc.)

Sometimes people use the term "ISO image" to refer to a copy of an operating system's installer. This is simply because so many operating systems have been installed from an optical disc that was created using a file in the ISO 9660 file format. Before USB storage devices were sufficiently large and cheap, many people used removable and easily re-writable media (such as USB or floppy disks) for small collections of data, like a word processing document (or a few), while they used ISO 9660 images to write to CDs when using a larger amount of data, such as the data that an operating system installer used.

To create an ISO image, people can use software such as "mkisofs" for Unix-type operating systems, or support that is built into Windows XP SP2 and newer (using Windows Explorer). Before Microsoft started including such capabilities built into Windows, people often acquired third party software, such as "Nero Burning ROM". Today, there are also additional options that are freely available for Microsoft Windows users, such as InfraRecorder or ImgBurn.

Very often, people want to use the ISO image to have a computer run code from a disc when the computer is starting up. This means that the ISO image needs to be "bootable". Back in the day, this traditionally involved creating a "bootable" image of a floppy disk. Then, software could use that bootable disk image, and combine that data with other data that is desired to be part of an ISO image, and the end result would be a bootable ISO image. A common method for doing this was to use a standard called "El Torito". Other discs have been known to use other methods. Compatibility could vary based on factors like what system startup software ("BIOS") a computer used.

The most common way that ISO images are used is to write them to removable media. With newer versions of Microsoft Windows, there is an "ISOBURN.EXE" built into the operating system. If that software is undesirable for any reason (such as being unavailable on other platforms, including older versions of Microsoft Windows), people can often other software that is bundled with an operating system, or installed separately. (For instance, Unix may have "cdrecord" or clones/successors like cdrkit.)

Additionally, some software can extract files from an ISO image. 7-Zip is a great example (available for Unix and also Microsoft Windows).

One peculiarity of the ISO 9660 image is that it is relatively easy to create an ISO 9660 image, but there is very little support to do much to modify data that is in an ISO 9660 image. Instead, people typically just acquire all of the desired contents of an ISO 9660 image, and create a new ISO 9660 image (if an updated image is desired). The downside to this approach is that it takes more disk space, and might take longer. Presumably the upside is lessened complexity for the software that handles the image. If people want to use an image on an optical disc, and they want to be able to update the image, people typically choose a different file format (such as UDF. UDF on DVDs is more common than UDF on CDs).

  • Very helpful explanation, thank you! When you say: "use the ISO image to have a computer run code from a disc when the computer is starting up" is there a particular location or name for this code? I'm trying to imagine the very first few lines a computer utilizes when booting from an ISO. – Robert Houghton Feb 3 '20 at 15:06
  • 1
    @RobertHoughton : "boot code". Although, some people might consider any code in the boot process to be "boot code". The entire disc may also be described as a "boot image". With the "El Torito" design, part of the CD image would be data similar to what went onto a floppy disk, so the "boot image" could refer to just data from that part of the entire CD image. The "first few lines" a computer runs is in ROM chips, and called the firmware (historically BIOS was common, now (U)EFI is more common). Such firmware runs "boot code" that, typically, then finds the rest of the operating system. – TOOGAM Feb 3 '20 at 18:09

This may take awhile. I won't get into "the weeds" since this is a process you have to feel you way through.

  1. In the beginning "read here just after the age when mainframes" roamed the corporate hinterlands" I saved operating systems to disk (5-1/4 and 3 1/2 disks) and the world was bright and full of hope.

  2. Then came the era of large PC operating systems and disks and I used Iomega drives to save backup images of my systems.

3.Next came ghost a wonderful imaging program to save my 95-NT 4 systems. I even created a way to use it with XP.

Now we are in the age of massive drives and operating systems.

This is what I do. 1. Yes, I do backups frequently of my files. But, when I got a new PC it came with a disk image on a CD. then the CD was removed and I had to cast around for another solution. Yes, MS has backup utilities in the OS, but I found it lacking. Gizmo's site has a list of utilities.

My goal was to get a system on self-booting and installing disks.

I have tried everything from Drive Image XML to Acronis i.e. Paragon, AOMEI, Macrium etc. They all work and unfortunately break sporadically and silently every so often. And you will never know until you try them or test them. Be warned!

2 So right out of the box (brand new computer) I pick one of the afore mentioned products and create an image to disk and test install it to a secondary or portable hard drive. If that works I save this as my final "when all fails" go to. I also go to the manufacturer's site and save off all the drivers etc. to CD.

3.Then I take my system and remove all the crapware, add my "stuff" i.e. customized boot screen, desktop manager, software etc.

  1. When I get a fall back customized setup I like I make another image and test it. IF everything is a go, I setup a backup plan for saving any new drivers, programs etc. and other changes so I can re-install my customized image and add the ongoing "stuff" until it becomes a hassle and then create a new customized image. Repeating as needed.

  2. Recently, I have been using Linux tools, so far they are a pain in the "you know what", but they are more reliable and give me the option of saving dual boot machines with a little more work, but better results. This is one of the many junctures that makes setting up a step by step "how to" problematic.

You will have to "experiment" with the level of pain you are willing to take and the results you want i.e. which tool you like after a test drive or two. unfortunately, like most of life this isn't simple or easy, especially the first few times. Yes, it is not easy initially, yes it is a pain, yes you should read all the "how to" and help files you can get. I had to luxury to grow along with the technology, but if I was going to start doing this now from scratch I would use an older computer to "practice" with first.

But if you are willing to dare greatly, the reward is worth it. Like, late some Friday night when your PC goes belly up and you are on deadline. With this method, system? You just get something to drink, install from your DVDs and in about an hour or so you will be good to go.

  • What... in the world are you talking about? The user is asking about what an ISO is, not on how to backup your system. – Nelson Jan 9 '16 at 2:54
  • Horrible history lesson about Windows. This does not explain in detail what an .ISO is beyond what has already been provided by existing answers. Statements like "My goal was to get a system on self-booting and installing disks." don't belong in answers. – Ramhound Jan 9 '16 at 6:05

When you would like to copy your OS disk into another disk / HDD you can create an .iso format image.You can run it by using virtual cd tools like Daemon Tools / Power ISO or write your ISO file to an other cd/dvd to use it later.

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