DDon’t You Love ISOs?

(No, that's not a typo....)

I do, especially when they’re used with virtualization. Though one problem I’ve had with ISO files -- those that need to be bootable -- is finding an ISO creation application that consistently creates one that works.

Tools like WinISO and Nero can create ISO files out of existing CD and DVD media. But I’ve had issues with consistently getting their ISOs to boot inside my virtual machines. One tool that consistently works, though, is the Unix command, “dd.”

The dd command has been around in Unix since 1975, and was originally used for low-level copying and conversion of files as well as reading and writing to block-based media like tape drives. For our purposes, we can use it to do a block-level transfer from a mounted CD-ROM into an ISO file.

Most Linux distributions include dd as part of the native command set. So, use of this tool will require a Unix or Linux server in your environment. If you’re using VMware ESX, its Linux-based operating system already includes the tool.

To use dd, do the following:

Put the CD in the drive.

Enter less /etc/fstab and check the results for the path to your CD-ROM drive. Depending on the configuration of your server, that path may resemble “/dev/cdroms/cdrom0”.

Type mount /dev/cdroms2/cdrom0 /mnt/cdrom to mount the drive. You’ll need to do this if you’ve not configured the server to automount the CD-ROM device as its inserted.

Enter dd if=/dev/cdrom of={Name of ISO} to create the ISO file.

Using dd, the process of ripping even DVDs to ISOs is remarkably quick, taking only a few minutes to complete. The extra bonus of using this command directly on your ESX server is that you can save the extra step of having to copy the resulting file to its target location.

About the Author

Greg Shields is Author Evangelist with PluralSight, and is a globally-recognized expert on systems management, virtualization, and cloud technologies. A multiple-year recipient of the Microsoft MVP, VMware vExpert, and Citrix CTP awards, Greg is a contributing editor for Redmond Magazine and Virtualization Review Magazine, and is a frequent speaker at IT conferences worldwide. Reach him on Twitter at @concentratedgreg.


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