"/etc/init.d/mysql start" fails, so package can't be configured

[Bogdan Butnaru]

Up to date Jaunty, on amd64:

$ dpkg -C
The following packages are only half configured, probably due to problems
configuring them the first time. The configuration should be retried using
dpkg --configure <package> or the configure menu option in dselect:
 mysql-server-5.1 MySQL database server binaries

bogdanb@mabelode:/var/cache/pbuilder/result$ sudo dpkg --configure mysql-server-5.1
Setting up mysql-server-5.1 (5.1.30-2ubuntu2) ...
 * Stopping MySQL database server mysqld [ OK ]
 * Starting MySQL database server mysqld dpkg: error processing mysql-server-5.1 (--configure):
 subprocess post-installation script returned error exit status 255
Errors were encountered while processing:
 mysql-server-5.1

bogdanb@mabelode:/etc/init.d$ sudo mysql start
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

ProblemType: Package
Architecture: amd64
DistroRelease: Ubuntu 9.04
ErrorMessage: subprocess post-installation script returned error exit status 1
Package: mysql-server-5.1 5.1.30-2ubuntu2
SourcePackage: mysql-dfsg-5.1
Title: package mysql-server-5.1 5.1.30-2ubuntu2 failed to install/upgrade: subprocess post-installation script returned error exit status 1
Uname: Linux 2.6.28-4-generic x86_64