mysql works, mysqldump doesn't

I have mysql 5.5 on my ubuntu 12.04 server. This command:

mysql -u root -p

works perfectly, but this gives me error:

mysqldump -u root -p mydb_name > a.sql
mysqldump: Got error: 2002: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) when trying to connect

In my.cnf file, the socket is set to:

socket = /home/mysql/mysql.sock

so I have no idea where /var/run/mysqld/mysqld.sock is coming from. Thanks.

When reading the configuration file, the mysql command line client only reads configuration directives found in the [client] and [mysql] sections, while mysqldump only uses configuration directives found in the [client] and [mysqldump] sections.

If your socket directive in the config file is in the [mysql] section but not the [mysqldump] section then you should move it to the [client] section, and this should solve your problem.

So where does /var/run/mysqld/mysqld.sock come from? I remember very distinctly, once upon a time, beating my head against the wall repeatedly over that one.

It turns out, Ubuntu compiles their MySQL components from source, and when they do that, they compile them to use /var/run/mysqld/mysqld.sock unless the configuration file specifies otherwise or the socket is overridden on the command line... so if your socket directive isn't in [client] that would be one explanation of this behavior.

StackExchange Database Administrators Q#46296, answer score: 9