This question already has an answer here:
I use Kubuntu and recently upgraded to Raring directly from Precise.
Until Precise, I always installed the OS using the alternate CD and not the desktop CD, because I could later on mount the image and use it as an offline package repo. For instance if I remove a package installed by the default installer and later I want to install it again, I can just install it from the ISO without needing to download it again.
However, since Quantal the alternate CD no longer exists, so I am not sure how to set up the installed image as a local repo. I mean, doing find . -name "*.deb" inside the ISO tree after loopmounting it only shows a few packages like libc6 gcc and such and not the full set of packages that are actually installed -- I presume they are included in pre-installed form inside casper/filesystem.squashfs.
Given this situation, is it or is it not possible to use the Raring install images as offline repos? If yes, how?
Edit: Quite a few people marked this as a dup of: How to use a .iso image as a CD-ROM Repository? but the steps outlined there (that thread is from 2010) do not work with the Raring image. IIUC they would work only with the alternate images and they are not available any more. So anyway I tried those instructions and did:
$ mount | grep loop
/mnt/sda8/samjnaa/ai/ubuntu/raring/kubuntu-13.04-desktop-amd64.iso on /mnt/loop0 type iso9660 (ro)
$ sudo apt-cdrom -d /mnt/loop0/ add
Using CD-ROM mount point /mnt/loop0/
Waiting for disc...
Please insert a Disc in the drive and press enter
E: Failed to mount the cdrom.