How to add an iso file as APT source

Question

Say I have this line in "/etc/fstab":

/iso/apt.iso /mnt/apt iso9660 loop 0 0

And I run these commands as root:

mount --all
apt-cdrom add --no-mount --cdrom /mnt/apt

I expected the disk to be added as APT source, but nothing happens. What's missing?

UPDATE:

I followed this advice and now I'm getting this:

Using CD-ROM mount point /media/cdrom/
Identifying.. [61c5dd7c11a32dc999e655c235cd698e-2]
Scanning disc for index files..
Found 0 package indexes, 0 source indexes, 0 translation indexes and 0 signatures
W: Failed to mount '/dev/sr0' to '/media/cdrom/'
E: Unable to locate any package files, perhaps this is not a Debian Disc or the wrong architecture?

This happens with or without "/etc/apt/apt.conf" changes.

Answer 1

here's what worked for me:

first, the line in /etc/fstab should look like this:

/iso/apt.iso /mnt/apt iso9660 user,loop 0 0

then, with the mount-point mounted, run apt-cdrom like this:

apt-cdrom -m -d=/mnt/apt add

if apt still asks you to insert the disk, add these lines to apt.conf

Acquire::cdrom::mount "/mnt/apt";
APT::CDROM::NoMount;

I think you should find this will work for you too :)

Answer 2

Mounting iso image to directory

mkdir /mnt/hp
mount -o loop /root/HPE_ProLiant_Value_Add_Software-10.80-1.iso /mnt/hp

apt-cdrom examines dir contents and generates entries in /etc/apt/sources.list

apt-cdrom --no-auto-detect --no-mount --cdrom /mnt/hp/ add

Entries looks like this

deb cdrom:[HP Management Component Pack 10.80]/ bionic 10.80/non-free
deb cdrom:[HP Management Component Pack 10.80]/ stretch 10.80/non-free
deb cdrom:[HP Management Component Pack 10.80]/ xenial 10.80/non-free

Replace cdrom-stuff in entries with link to mountpoint, also i had to add [trusted=yes] to evade outdated keys issues

deb [trusted=yes] file:/mnt/hp/ bionic 10.80/non-free
deb [trusted=yes] file:/mnt/hp/ stretch 10.80/non-free
deb [trusted=yes] file:/mnt/hp/ xenial 10.80/non-free

Make sure your iso is still mounted when using apt.