Here are ways that you can convert dmg files to iso files on Mac OSX, Windows and Linux.
Before we start, let’s download a dmg file from the public domain. I found one on Apple’s article about The XMLHttpRequest Object website while I was learning Ajax and that can be downloaded from this link. This is just a 150KB dmg file and will be handy if you want to have something to test with while you’re following this tutorial.
How to convert dmg files to iso files on Mac
Method 1: Using the Mac terminal
1. Open a terminal window from Finder > Applications > Utilities > Terminal.
2. Assuming that you have a disk image called apple.dmg in the current directory, type
hdiutil convert apple.dmg -format UDTO -o apple.iso
3. This will actually create a file called image.iso.cdr in the current directory (even though we asked for the output to be image.iso). This file can be safely renamed to image.iso, copied to a Windows server or machine, and burned with your CD/DVD burner of choice.
Generally, the command hdiutil can be used this way:
hdiutil convert /path/to/filename.dmg -format UDTO -o /path/to/savefile.iso
Method 2: Using DMGConverter (freeware)
1. DMGConverter is a disk image (.dmg, .cdr, .iso) creation and conversion tool which is simple and easy to use. It is a very useful tool for the collective processing of more than one file and every folder, and it can deal with all the fundamental processing with the drag & drop of the file/folder. For Mac Only.
How to convert dmg files to iso files on Windows
This is for Windows users who might have downloaded a dgm file and wondering how to extract the content, or not even knowing how and what to do with the dgm file. I’ve been there at a certain stage. the sharewares mentioned are fully functional and allows you to use the “convert dmg to iso” function even when it’s not registered yet.
Method 1: Using MagicISO (shareware)
1. Download MagicISO, install and run program.
2. Click 
to open dmg file.
3. Click 
to open “Properties” dialogs.
4. Uncheck Apple HFS and Apple HFS+
5. Check “ISO 9660″ “Joliet” “UDF”
6. Click OK
7. Click 
to save as to iso image, or click 
to burn to CD/DVD without saving.
Method 2: Using UltraISO (shareware)
UltraISO basically does the same thing, but it can save you time from doing step 3 to 6 compared to method 1.
Alternative Solutions: dmg2iso (freeware) and isobuster (shareware)
I’ve heard and read that some people had been able to convert dmg files into iso files using dmg2iso (freeware). I’ve tried dmg2iso, converted my dmg file to iso without problem, but the converted iso file is corrupted and can’t be open by any tools (Daemon Tools, Alcohol, MagicISO, UltraISO and ISOBuster) that I’ve tested. It might work for you, but no guarantees.
ISOBuster is pretty similar to MagicISO and UltraISO. But too bad that the function to “convert dmg to iso” is restricted and won’t be functional until you buy the software.
How to convert dmg files to iso files On Linux
Free open-source app AcetoneISO provides a great deal of disc image manipulation tools not found in the Gnome desktop. It can mount/unmount a variety of image formats (ISO, DMG, MDF, NRG, BIN, NRG), convert images, create, encrypt, and decrypt ISOs, play DVDs (with the required codecs installed), and much more. It is particularly useful for mounting proprietary formats found in Windows and Mac boot discs. AcetoneISO is a one-stop-shop for all of your CD/DVD image manipulation needs, and is a free download for Linux only. This works on all famous linux distro such as Ubuntu, SUSE, Fedora, Mandrake, and Redhat.
So there you have it, and this should get you covered no matter what operating system you’re using.
