apt-cdrom on iso mount

[Nick Wright <nick@lsd.net.nz>]

I'm having some trouble getting apt to use a mounted .iso image on my
hdd.

I've set it up in my /etc/fstab as:

/root/debian-31r2-i386-binary-1.iso /mnt/deb_iso1 iso9660 loop,ro 0 0

and then ran the following

# apt-cdrom -d /mnt/deb_iso1 -m add
Using CD-ROM mount point /mnt/deb_iso1/
Identifying.. [bc7d47aca21b2972f0aaf5a21ff1fbd4-2]
Scanning Disc for index files..  Found 2 package indexes and 0 source indexes.
This Disc is called:
 'Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)'
Reading Package Indexes... Done
Wrote 7051 records.
Writing new source list
Source List entries for this Disc are:
deb cdrom:[Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)]/ unstable contrib main
Repeat this process for the rest of the CDs in your set.

no problem so far..

I now have this in my /etc/apt/sources.list:

deb cdrom:[Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)]/ unstable contrib main

and this in my /var/lib/apt/cdroms.list

CD::bc7d47aca21b2972f0aaf5a21ff1fbd4-2 "Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)";
CD::bc7d47aca21b2972f0aaf5a21ff1fbd4-2::Label "Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)";


aptitude update runs fine..

finally, I go to install a package:

# apt-get install apt-howto
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
  apt-howto-ca apt-howto-common apt-howto-de apt-howto-el apt-howto-en
  apt-howto-es apt-howto-fr apt-howto-it apt-howto-ja apt-howto-ko
  apt-howto-pl apt-howto-pt-br apt-howto-ru apt-howto-tr
The following NEW packages will be installed:
  apt-howto apt-howto-ca apt-howto-common apt-howto-de apt-howto-el
  apt-howto-en apt-howto-es apt-howto-fr apt-howto-it apt-howto-ja
  apt-howto-ko apt-howto-pl apt-howto-pt-br apt-howto-ru apt-howto-tr
0 upgraded, 15 newly installed, 0 to remove and 0 not upgraded.
Need to get 0B/3894kB of archives.
After unpacking 6078kB of additional disk space will be used.
Do you want to continue? [Y/n] 
Media Change: Please insert the disc labeled
 'Debian GNU/Linux 3.1 r2 _Sarge_ - Official i386 Binary-1 (20060419)'
in the drive '/cdrom/' and press enter

And there's the problem -- why does it want to use /cdrom/ when I told
it the cdrom mount point was /mnt/deb_iso1?

Can I edit the sources.list file to override the cdrom mount point for
each .iso I want to use?

Thanks,

Nick