Recovering when di misleads Synaptic et al.

[Richard Owlett <rowlett@cloud85.net>]

This is *NOT* a bug report.

I have a _USED_ laptop set aside for learning and experimentation.
It has had as many as a half dozen clean installs in a single day ;/
The CD drive has finally died [no plans to replace].

With dd I have copied DVD 1 of Jessie to a USB flash drive.
Install from the flash work fine.

To add additional packages I must:

richard@debian-jessie:~$ su -l
Password:
root@debian-jessie:~# gsettings set org.mate.media-handling 
automount false
root@debian-jessie:~# mount -t iso9660 /dev/sdb /media/cdrom

Any simplifications, perhaps with preseeding?
TIA