See issue 719:

  * Check whether rebuild of ISO is needed even though the ISO exists already.
    [Closes: issue719]

Closing therefore.

I'm not sure whether using the -q option (skip mksquashfs) should really skip 
all the other checks as well. Especially the FAI part could be executed anyway 
so rebuilding e.g. the initramfs happens.

# grml-live -a i386 -s squeeze -c GRMLBASE,GRML_MEDIUM,RELEASE,I386 -o /grml-
live/grml-squeeze -v 2009.08.10 -g grml-squeeze -r squeeze-test -V -q

grml-live [0.9.20]: check your configuration (or use -F to force execution):

  FAI classes:       GRMLBASE,GRML_MEDIUM,RELEASE,I386
  local config:      /etc/grml/grml-live.local
  main directory:    /grml-live/grml-squeeze
  chroot target:     /grml-live/grml-squeeze/grml_chroot
  build target:      /grml-live/grml-squeeze/grml_cd
  ISO target:        /grml-live/grml-squeeze/grml_isos
  grml name:         grml-squeeze
  release name:      squeeze-test
  grml version:      2009.08.10
  Debian suite:      squeeze
  Architecture:      i386
  Boot method:       isolinux
  Logging to file:   /var/log/grml-live.log
  Using VERBOSE mode.
  Skipping creation of SQUASHFS file.

Is this ok for you? [y/N] y

 * Logging actions to logfile /var/log/grml-live.log
 * /grml-live/grml-squeeze/grml_chroot exists already, skipping stage 'fai 
dirinstall'                                                                                     [ ok ]
 * /grml-live/grml-squeeze/grml_cd/boot exists already, skipping stage 
'boot'                                                                                              [ ok ]
 * /grml-live/grml-squeeze/grml_cd/live exists already, skipping stage 
'squashfs'                                                                                          [ ok ]
 * /grml-live/grml-squeeze/grml_isos exists already, skipping stage 'iso 
build'                                                                                            [ ok ]
 * Successfully finished execution of grml-live [running 2 seconds]