Debian packages of the form -server-core- provide binaries for MySQL and variant server daemons only. These are intended for users who wish to manage database data directories and daemon and service configurations themselves. Debian packages of the form -server- depend on the corresponding -server-core- packages and add automatic management of database data directories and daemon and service configuration via maintainer scripts. It is possible for a -server- maintainer script to detect a local customisation that means that it cannot continue. Each known case is documented in a separate file in this directory. When such a situation arises, the -server- maintainer scripts will enter "frozen mode". We consider this preferable to the maintainer script failing with a non-zero return code, which was the previous behaviour. The previous behaviour would cause dpkg to fail, causing apt to fail, leaving system packaging in a broken state and causing a release upgrade to fail for example. This seemed excessive for what could be an intended configuration change by the user. Instead, "frozen mode" stops the -server- maintainer scripts from making changes until the user intervenes. The maintainer scripts will not start the daemon, perform database upgrades or make similar changes. When "/etc/mysql/FROZEN" exists (even if it is a broken symlink), then frozen mode is defined to be turned on. Usually a maintainer script turning frozen mode on will create a symlink at /etc/mysql/FROZEN pointing to further documentation on the specific case encountered in this directory with an explanation and suggestions for resolution. To resolve frozen mode, resolve the situation documented by /etc/mysql/FROZEN and only then remove the /etc/mysql/FROZEN symlink, and run "dpkg-reconfigure " where should usually be in the form -server-.