Ho provato a seguire quei consigli ma nulla di fatto:

root@giuseppe-laptop:/var/run/mysqld# kill `cat /mysql-data-directory/mysqld.pid`
cat: /mysql-data-directory/mysqld.pid: Nessun file o directory
kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ... or kill -l [sigspec]
root@giuseppe-laptop:/var/run/mysqld# ls
root@giuseppe-laptop:/var/run/mysqld# cp /home/giuseppe/mysqld.pid /var/run/mysqld/mysqld.pid
root@giuseppe-laptop:/var/run/mysqld# ls
mysqld.pid
root@giuseppe-laptop:/var/run/mysqld# mysqld_safe --init-file=mysqld.pid &
[1] 20763
root@giuseppe-laptop:/var/run/mysqld# Starting mysqld daemon with databases from /var/lib/mysql
mysqld_safe[20805]: started
STOPPING server from pid file /var/run/mysqld/mysqld.pid
mysqld_safe[20823]: ended

[1]+ Done mysqld_safe --init-file=mysqld.pid
root@giuseppe-laptop:/var/run/mysqld# mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (111)
root@giuseppe-laptop:/var/run/mysqld#

Aiuto!!