ISO images may be mounted in the file system similar to a physical cd or dvd. This is done in the same way as you mount any other device, '''mount''' only needs a few directions: 

{{{
mount -o loop -t iso9660 <source iso> <target dir>
}}}

for example: 

{{{
mount -o loop -t iso9660 ubuntu.iso /media/myiso
}}}

If you are frequently using ISOs it may be more convenient to apply a Nautilus script for the task, see [[http://doc.gwos.org/index.php/Mount_ISO_script]]

You can apply this to dist-upgrading from an image file without burning a CD.  When you do {{{apt-cdrom}}} or {{{synaptic}}} or how ever you want to add the CD, run 
{{{
sudo mount -o loop /path/to/cd/image.iso /cdrom
}}}
when it asks for you to insert the CD.  The package utilities like to unmount /cdrom when they see there is no physical disk in the CDROM drive, so you have to run the command only after it fails to find a physical CD.


See also: specification for ImageMounting