ISO files offer an advantage to virtual machines (VMs), chiefly as a means of loading operating systems and applications on virtual servers without the hassle of using physical media. Many tools for creating, editing and mounting ISOs are readily available and if you haven’t been creating ISOs already, keep reading.
An ISO file is an archive file format (ISO 9660), typically an image of a CD-ROM or DVD-ROM, similar to a .ZIP file but without file compression. An ISO can be any size, from a few megabytes to several gigabytes. Reading an ISO file is much faster than reading from physical media like CD-ROMs. Free from physical imperfections, ISO files are easy to mount on VMs and don’t require looking for a CD when it is needed.
I’ve created dozens of ISO files for different operating systems and applications. For my Windows servers, I no longer copy the I386 directory to the server since I can easily mount it as an ISO file on my virtual machines as needed, saving disk space on the VM. I also create ISO files with troubleshooting tools like the Sysinternals utilities, so I can mount them quickly to troubleshoot problems on my VMs. Once an ISO library is created, a central repository on a host datastore or remote server can be made using NFS or Samba to provide access to all VMs.
A number of applications are available to mount ISO files on a physical system by creating a virtual CD-ROM drive. Once mounted, contents of an ISO file can be accessed just like a physical CD-ROM drive. Linux and ESX systems can use the mount command to do this, while Microsoft provides for a little-known virtual CD-ROM driver that you can be downloaded for free. ISO files can be created and edited with other tools. Linux and ESX systems come installed with a command called dd that creates an ISO file from an input device like a CD-ROM or DVD-ROM. Microsoft provides a tool called cdburn in their downloadable Resource Kits. For your convenience, I’ve created a short list of some of the many tools available for creating, editing and mounting ISO files.
Tools to create and edit ISO files:
- cdburn.exe (available in Windows XP and Server 2000/2003 Resource Kits)
- dd.exe (Linux utility)
- ISO recorder
Tools to mount ISO files:
- Microsoft Virtual CD-ROM Control Panel
- Alcohol 52%(requires browser toolbar installation)
- Daemon Tools Basic (ad driven)
- mount.exe (Linux utility)
A more complete list of ISO resources can be found here.