IMGMOUNT

(excerpt from official DOSBox Readme)

IMGMOUNT

 A utility to mount disk images and CD-ROM images in DOSBox.
 
 IMGMOUNT DRIVE [imagefile] -t [image_type] -fs [image_format] 
           -size [sectorsbytesize, sectorsperhead, heads, cylinders]

 imagefile
     Location of the image files to mount in DOSBox. The location can
     be on a mounted drive inside DOSBox, or on your real disk. It is
     possible to mount CD-ROM images (ISOs or CUE/BIN) as well, if you
     need CD swapping capabilities specify all images in succession.
     The CDs can be swapped with CTRL-F4 at any time.
  
 -t 
     The following are valid image types:
       floppy: Specifies a floppy image or images.  DOSBox will automatically 
               identify the disk geometry ( 360K, 1.2MB, 720K, 1.44MB, etc).
       iso:    Specifies a CD-ROM iso image.  The geometry is automatic and 
               set for this size. This can be an iso or a cue/bin.
       hdd:    Specifies a harddrive image. The proper CHS geometry 
               must be set for this to work.

 -fs 
     The following are valid file system formats:
       iso:  Specifies the ISO 9660 CD-ROM format.
       fat:  Specifies that the image uses the FAT file system. DOSBox will attempt
             to mount this image as a drive in DOSBox and make the files 
             available from inside DOSBox.
       none: DOSBox will make no attempt to read the file system on the disk.
             This is useful if you need to format it or if you want to boot 
             the disk using the BOOT command.  When using the "none" 
             filesystem, you must specify the drive number (2 or 3, 
             where 2 = master, 3 = slave) rather than a drive letter.  
             For example, to mount a 70MB image as the slave drive device, 
             you would type:
               "imgmount 3 d:\test.img -size 512,63,16,142 -fs none" 
               (without the quotes)  Compare this with a mount to read the 
               drive in DOSBox, which would read as: 
               "imgmount e: d:\test.img -size 512,63,16,142"

 -size 
    The Cylinders, Heads and Sectors specification of the drive.
    Required to mount hard drive images.
    
 An example how to mount CD-ROM images:
   1a. mount c /tmp
   1b. imgmount d c:\myiso.iso -t iso
 or (which also works):
   2. imgmount d /tmp/myiso.iso -t iso

(excerpt from official DOSBox Readme)