Changing source for packages: lines in sources.list apt.conf.d 00knoppix

[rajibando]

I wish to change the default source for Synaptic. I changed the line in:

/etc/apt/apt.conf.d/00knoppix

From:

APT::Default-Release "wheezy";

To:

APT::Default-Release "squeeze-backports";

and

/etc/apt/sources.list

From:

deb http://ftp.de.debian.org/debian stable main contrib non-free

and other lines
To:

deb http://ftp.de.debian.org/debian-backports/ squeeze-backports main non-free

The original files have been renamed and kept, and can be restored.
Synaptic gives this error message

E: The value 'squeeze-backports' is invalid for APT::Default-Release as such a release is not available in the sources
E: _cache->open() failed, please report.

and closes.
What more needs to be done?
The change is required to clean reinstall nvidia drivers and repair the following error codes as Output:
Synaptic_Changes_Applied_terminal.txt
For nvidia drivers the following errors are known to the system:

ERROR: The conflicting library '/usr/lib/i386-linux-gnu/libGL.so.1.2.0' is known to dpkg.

[rajibando]

Backport is deprecated, I read in the instructions http://backports.debian.org/Instructions/
So, when I write squeeze-backports in 00knoppix in

/etc/apt/apt.conf.d

I get the following errors.

aptitude update
E: The value 'squeeze' is invalid for APT::Default-Release as such a release is not available in the sources
E: The value 'squeeze' is invalid for APT::Default-Release as such a release is not available in the sources
Hit http://download.jitsi.org unstable/ Release.gpg
Hit http://download.jitsi.org unstable/ Release   
Ign http://ftp.debian.org squeeze-backports Release.gpg
Hit http://download.jitsi.org unstable/ Packages
Ign http://ftp.debian.org squeeze-backports Release
Ign http://download.jitsi.org unstable/ Translation-en_US
Ign http://download.jitsi.org unstable/ Translation-en
Err http://ftp.debian.org squeeze-backports/main i386 Packages
  404  Not Found [IP: 130.89.148.12 80]
Err http://ftp.debian.org squeeze-backports/contrib i386 Packages
  404  Not Found [IP: 130.89.148.12 80]
Err http://ftp.debian.org squeeze-backports/non-free i386 Packages
  404  Not Found [IP: 130.89.148.12 80]
Ign http://ftp.debian.org squeeze-backports/contrib Translation-en_US
Ign http://ftp.debian.org squeeze-backports/contrib Translation-en
Ign http://ftp.debian.org squeeze-backports/main Translation-en_US
Ign http://ftp.debian.org squeeze-backports/main Translation-en
Ign http://ftp.debian.org squeeze-backports/non-free Translation-en_US
Ign http://ftp.debian.org squeeze-backports/non-free Translation-en
80% [Working]W: Failed to fetch http://ftp.debian.org/debian/dists/squeeze-backports/main/binary-i386/Packages: 404  Not Found [IP: 130.89.148.12 80]
W: Failed to fetch http://ftp.debian.org/debian/dists/squeeze-backports/contrib/binary-i386/Packages: 404  Not Found [IP: 130.89.148.12 80]
W: Failed to fetch http://ftp.debian.org/debian/dists/squeeze-backports/non-free/binary-i386/Packages: 404  Not Found [IP: 130.89.148.12 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
E: Couldn't rebuild package cache
E: The value 'squeeze' is invalid for APT::Default-Release as such a release is not available in the sources
E: The value 'squeeze' is invalid for APT::Default-Release as such a release is not available in the sources

I read the page on backport and the section on Installation from backport

Install a package from backports
All backports are deactivated by default (i.e. the packages are pinned to 100 by using ButAutomaticUpgrades: yes in the Release files. If you want to install something from backports run:

apt-get -t squeeze-backports install "package"

of course you can use aptitude as well:

aptitude -t squeeze-backports install "package"

After necessary amendments, when I type aptitude update, I get the following error message:

aptitude update
E: The value 'squeeze-backports' is invalid for APT::Default-Release as such a release is not available in the sources
E: The value 'squeeze-backports' is invalid for APT::Default-Release as such a release is not available in the sources
Hit http://download.jitsi.org unstable/ Release.gpg
Hit http://download.jitsi.org unstable/ Release
Hit http://download.jitsi.org unstable/ Packages
Ign http://http.debian.net squeeze-backports(-sloppy) Release.gpg
Ign http://http.debian.net squeeze-backports(-sloppy) Release
Ign http://download.jitsi.org unstable/ Translation-en_US
Ign http://download.jitsi.org unstable/ Translation-en
Err http://http.debian.net squeeze-backports(-sloppy)/main i386 Packages
  404  Not Found
Ign http://http.debian.net squeeze-backports(-sloppy)/main Translation-en_US
Ign http://http.debian.net squeeze-backports(-sloppy)/main Translation-en
83% [Working]W: Failed to fetch http://http.debian.net/debian-backports/dists/squeeze-backports(-sloppy)/main/binary-i386/Packages: 404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
E: Couldn't rebuild package cache
E: The value 'squeeze-backports' is invalid for APT::Default-Release as such a release is not available in the sources

E: The value 'squeeze-backports' is invalid for APT::Default-Release as such a release is not available in the sources

What is my mistake?

[rajibando]

There is an error in the file /etc/apt/apt.conf.d/00knoppix in declaring the stable package. Discussed in post: Flash Player no longer Directly Supports Linux .

...the second line sets ... default release ...Wheezy in Knoppix 7.2.0 ... prevents a sizeable number of packages from being marked as upgradable ... Before commenting out this line ...

The default apt line needs to be hashed. I will now try the next step: changing my nvidia drivers...

[Werner P. Schulz]

There is an error in the file /etc/apt/apt.conf.d/00knoppix in declaring the stable package.

Why do you think so?

Please read more about solving problems
Administrators Handbook => 6.2
Debian Reference => 2.7

[rajibando]

From the Debian Manual :

A cache is a temporary storage system used to speed up frequent data access when the usual access method is expensive (performance-wise). This concept can be applied in numerous situations and at different scales, from the core of microprocessors up to high-end storage systems.
In the case of APT, the reference Packages files are those located on Debian mirrors. That said, it would be very ineffective to go through the network for every search that we might want to do in the database of available packages. That is why APT stores a copy of those files (in /var/lib/apt/lists/) and searches are done within those local files

I changed /etc/apt/sources.list and /etc/apt/apt.conf.d/00knoppix (double-slashing '//), as pasted below;

// Debian/squeeze is the "stable" release for this version of KNOPPIX
// APT::Default-Release "wheezy";
Apt::Get::Purge;
APT::Force-LoopBreak 1;
APT::Cache-Limit 80000000;
// Acquire::http::timeout 36000;
// Acquire::http { Proxy "http://localhost:9999"; };

and removed the list database from /var/lib/apt/lists but synaptic still responds like it did when those changes were not included, and reports:

E: The value 'wheezy' is invalid for APT::default-Release as such a release is not available in the sources
E: _cache->open() failed, please report.

D replaced by ::d as the system is converting the characters into a smiley.

[rajibando]

Apt is obedient.
only Synaptic is creating all sorts of problems...

[rajibando]

Correction! apt-get update is obedient when synaptic is not. apt-get install *nvidia* is showing the error line once. Synaptic shows the error line when invoked, and when ok is pressed, it exits. Tasksel, when invoked, shows the error line numerous times and exits. The error lines, as stated earlier, are displayed despite the 2nd line in /etc/apt/apt.conf.d/00knoppix has been silenced.
So apt must be accessing another configuration file from somewhere.
The maintainers of Apt appear to be oblivious of the fact that while apt.conf is nowhere to be found, apt still has the file mentioned in its list of files.

[rajibando]

This reason is this: Apt is the culprit

APT's Default Priority Assignments
If there is no preferences file or if there is no entry in the file
that applies to a particular version then the priority assigned to that
version is the priority of the distribution to which that version
belongs.

[rajibando]

Ultimately, I saw reason and installed the latest downloaded Unix/Linux driver from nvidia and resolved the conflicts rather than an uneasy living with a conflicted, debian reconfigured nvidia.