MySQL service won't start

Question

I've just rebooted my Ubuntu server and MySQL just won't start for some reason! I'm using:

/etc/init.d/mysql start

I just get this:

 * Starting MySQL database server mysqld                         [fail]

Why might this be happening? Apache is running and my site works OK apart from the database connection. MySQL server is installed normally via synaptic.

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I ran:

sh -x /etc/init.d/mysql start

Which listed this among the output:

+ echo -e 0 processes alive and '/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf ping' resulted in\n/usr/bin/mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)'
Check that mysqld is running and that the socket: '/var/run/mysqld/mysqld.sock' exists!\n

I followed the advice here for creating the .sock file but no luck.

(Let me know any more information you need me to provide.)

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Update: I ran mysqld since the output above mentioned it, and got this error:

100516 17:37:57  InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name ./ibdata1
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.

Any idea what it means, or what file it refers to?

Answer 1

Success! As mentioned in the question update, running mysqld gave some errors. I found the files and realized that the entire /var/lib/mysql directory had the wrong owner (root instead of mysql). This was due to the partition swap and file moving I did.

So I ran:

chown -R mysql /var/lib/mysql/

Then running mysqld followed by the regular MySQL start command fixed everything.

Thanks to everyone who helped!

Answer 2

while restarting mysql run

tail -f /var/log/syslog

and observe what's going on there. maybe you've run out of disk space on data / log partitions.