First of all Debian jessi (Debian 8.0) is out (released April 25th).
But as we know it will take a bit until all software especially non-free will be ready anf who would do an upgrade of all their servers within the first weeks? As a good admin of your servers you may update your servers regularly. In my case most my server install their updates nightly automatically via the unattended-upgrades. Config file most commonly found at /etc/apt/apt.conf.d/50unattended-upgrades .
After a weekend not receiving any notifications about about updates, I had a look around.
Digging through logs, spam filters, and mail queues I could not find a reason. Usually I am not updating the servers manually via apt-get upgrade or dist-upgrade as this may bring more updates as I need and/or instability or worst a reboot. Furthermore would no one configure their automatic updates to do more the necessary updates like security. By executing the commands manually I came closer to the problem, the keys are not valid any more.
apt-get clean && apt-get update; Hit http://ftp.nz.debian.org wheezy-updates Release.gpg Hit http://ftp.nz.debian.org wheezy Release.gpg Hit http://ftp.nz.debian.org wheezy-updates Release Hit http://ftp.nz.debian.org wheezy Release ... Reading package lists... Done W: There is no public key available for the following key IDs: 7638D0442B90D010 W: There is no public key available for the following key IDs: 7638D0442B90D010 W: There is no public key available for the following key IDs: 9D6D8F6BC857C906
A look where we are on the server:
xyz-web4:~# lsb_release -a Distributor ID: Debian Description: Debian GNU/Linux 7.7 (wheezy) Release: 7.7 Codename: wheezy
As mentioned before, you would never do a dist-upgrade automatic at night. To solve the problem we can ether upgrade manually the one trouble package or the entire system to the latest wheezy packages via apt-get dist-upgrade.
If you do not want to upgrade the whole system, you can upgrade the trouble package via
aptitude upgrade debian-archive-keyring
Full upgrade of all packages to latest wheezy version:
xyz-web4:~# apt-get dist-upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages will be upgraded: apache2 apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common apt apt-utils base-files debian-archive-keyring libapt-inst1.5 libapt-pkg4.12 libruby1.8 libruby1.9.1 linux-image-3.2.0-4-amd64 linux-libc-dev mercurial mercurial-common ruby1.8 ruby1.9.1 tzdata 20 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 38.3 MB of archives. After this operation, 2,500 kB of additional disk space will be used. Do you want to continue [Y/n]?
A look where we are now:
xyz-web4:~# lsb_release -a Distributor ID: Debian Description: Debian GNU/Linux 7.8 (wheezy) Release: 7.8 Codename: wheezy
And guess what, if you execute now apt-get update everything is fine.