You can mount DVD / CD iso images using loop module under Linux (Sun Solaris UNIX user can try out lofiadm command) . It would be good idea to increase the number of loop filesystems allowed to be mounted simultaneously by adding the following line to /etc/modprobe.conf file:

Task: Set maximum number of loop devices

Open Linux kernel module configuration file using text editor:
# vi /etc/modprobe.conf

Append loop module configuration parameter:
options loop max_loop=256

Where,
=> loop : module name

=> max_loop=256: Maximum number of loop devices (1-256)

This is useful on dedicated installation server. For example internally we have over 5 Linux distro ISO downloaded with new and old version number. We use iso for HTTP or FTP installation over LAN. By increasing limit to max you can avoid problems.