Unless the issue is already known/documented, it should be reported so it can be further investigated.
There are two possible reasons why this could happen, either there is an issue with the repository that the maintainers have to fix, or you are victim of a Man-in-the-middle_attacks. Just make sure, you never install unsigned packages as explained above. Otherwise anonymity/privacy/security settings deployed with Whonix might get lost.
Thus, when installing software with apt-get, you typically type simply makes sure your list of packages from all repositories and PPA's is up to date.
If you do not run this command, you could be getting older versions of various packages you are installing, or worse, dependency issues.
Your computer has a list (like a catalog) that contains all the available software that the Ubuntu servers have available.
But the available software and versions might change, so a "update" will hit the server and see what software is available in order to update its local lists (or catalogs). This is the step that actually retrieves information about what packages can be installed, including what updates to currently installed packages packages are available, from Internet sources.
These are not installed with an upgrade, as this command only updates the packages you already have installed.
W: Failed to fetch 404 Not Found W: Failed to fetch 404 Not Found E: Some index files failed to download. Err Could not resolve 'debian.org' Err Could not resolve 'deb.torproject.org' Err Could not resolve 'security.debian.org' Reading package lists... If not, something is broken or it’s a Man in the middle attack, which isn’t that unlikely, since we are updating over Tor exit relays and some of them are malicious. The repository is not updated and the previous index files will be used.
Done W: Failed to fetch not resolve 'security.debian.org' W: Failed to fetch not resolve 'debian.org' W: Failed to fetch not resolve 'deb.torproject.org' W: Some index files failed to download. GPG error: Release: The following signatures were invalid: KEYEXPIRED 1409325681 KEYEXPIRED 1409325681 KEYEXPIRED 1409325681 KEYEXPIRED 1409325681 will automatically ignore repositories with expired keys or signatures, you will not receive upgrades from that repository.
This version change requires several adjustments to configuration files, and can break an existing website.
Please follow our Upgrading Apache guide before continuing.
To update software in Raspbian, you'll need to use the apt tool in a terminal window.