I wanted to point my sources to "unstable" so that I could get the latest updates without waiting for a long time.

So I changed the mirrors in "sources.list" file to point to the "unstable" branch and then I did an apt-get update so that I could load the software on unstable (sid) branch.

But after the apt-get update synaptic does not show any packages to upgrade and the list doesn't show any of the packages as "available for upgrade". Instead it shows all packages present on my system as being up to date. Also many of the existing packages are shown as being "local or obsolete".

How do I convert my "testing" to "unstable" seamlessly and without losing any package upgrades available?

I'm sure there are a few more steps involved, but I'd be glad if somebody could help me with this.

Try using apt itself by using apt-get dist-upgrade or if there is an option in synaptic for it then dist-upgrade from it. If it still wants to keep you at testing then make sure you have a line like this in your /etc/apt/apt.conf.

My idea was to continue having "testing" for the base packages but still have the option of installing specific packages from "unstable" if needed. Is that a dangerous combination? I read that this is possible in the documentation, but I am wary of doing this.

Currently I have reverted all repositories back to testing.

No not really dangerous at all I have been doing that for a couple of years. You need to edit the /etc/apt/apt.conf and /etc/apt/preferences files and have them look like this.

The Default-Release line tells apt you want packages from testing, Show-Versions line shows you where the packages will be coming from when using apt-get and Cache-Limit increases the package cache limit so you can have more than one repository cached.

This tells apt that you want packages from testing over unstable during a normal install/upgrade. If you want to install packages from unstable then you use apt-get install -t unstable package_name and it will install the package you want. If you get errors saying that the package cannot be install because another package(s) is at a lower version than the unstable one you want needs then add the package(s) to the end of the line until it will install without the errors. You may want to look into using the -s option of apt-get to simulate the command then when every thing installs without errors remove the -s from the line and do the actual install, this allows you to check and make sure nothing you want from your install will get removed accidently because of conflicts. And of course you will need to have lines for both testing and unstable in your sources list like this changing the lines to reflect the mirror you are using.

Thanks HappyTux. I'll bookmark this thread and follow your instructions when I get the opportunity.

I've been wanting some packages from unstable, but I've really been quite wary of doing this. Now that you have shown the correct way, I'll follow this and tell you how I get on.

There is no file in my system named /etc/apt/apt.conf.

Just create the file then with the contents above and apt will use it.

Just wanted to add that I went to unstable and boy am I a happy camper. Everything is for the first time running as fast or faster than my best Xp machine.

System specs:
Rambus 1800mhz P4 system