>A package version pin is probably the way to go on this.
>
>Here's what I have in /etc/apt/preferences:
>
>========
>Package: iceweasel
>Pin: version 24.*
>Pin-Priority: 1001
>========
>
>I used something similar with 17.* until I was ready to upgrade (having
>tested first in a VM to make sure I knew how to fix anything that would
>break), and I expect to do it again with 31.* when the time comes.
>
>I used to use holds ("echo 'NAME hold' | dpkg --set-selections"), but
>that led to held-packages dependency breakage when dist-upgrading
>sometimes. I find that package version pinning works much better.
OK I can now to work on /etc/apt/preferences not apt.conf. Thanks.