Mysql server won't start - no logs

This message comes from the service script, not from mysql. So you have to look at the script and figure where/why it fails.

Do that by calling sh -x /etc/init.d/mysqld start.

note: on some questions, like this one, I don't see any "add comment". I only have the option to add an answer. How can I just add a comment ?

Same issue here, for me the reason was, that the my.cnf file has been moved from /etc/my.cnf to /etc/mysql/my.cnf, but there still was a "dead" symlink pointing to /etc/my.cnf.

Check if /etc/mysql/my.cnf is a symlink:

user@machine:~ $ ls -l /etc/mysql/my.cnf
lrwxrwxrwx 1 root root 9 Jan 11  2011 /etc/mysql/my.cnf -> ../my.cnf

If it is a symlink, check if the target file exists. If not, remove the symlink and create /etc/mysql/my.cnf from /etc/mysql/my.cnf.dpkg-new or something like that... if you have it.

sudo unlink /etc/mysql/my.cnf
sudo mv /etc/mysql/my.cnf.dpkg-new /etc/mysql/my.cnf

P.S: If the symlink's target is existing, you might want to check dmesg | grep cnf for apparmor error messages.

This problem can occur if the pid file still exists, such as after a crash. Check for that and delete it if it does exist.

The pid file location defaults to /var/run/mysqld/mysqld.pid but a different location may be set in the config file.