Tips
DDon’t You Love ISOs?
(No, that's not a typo....)
- By Greg Shields
- 08/27/2007
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 is an independent author, speaker, and IT consultant, as well as a Founding Partner with Concentrated Technology. With nearly 15 years in information technology, Greg has developed extensive experience in systems administration, engineering, and architecture specializing in Microsoft OS, remote application, and virtualization technologies. Greg is a Contributing Editor and columnist for TechNet Magazine, a former columnist for Redmond Magazine and Virtualization Review Magazine, and has authored or contributed to ten books and countless white papers and webcasts. His writing is regularly seen in publications like TechTarget online, e-books from Realtime Publishers, and the UK-based IT EXPERT Magazine. He has also produced numerous video training series for CBT Nuggets.