title: Mysql problem: no mysql.sock
body: <p>Yesterday I was working using MySQL installed on my computer.<br>
  I downloaded xampp, so I have I changed on <code>my.cnf</code> file the path to the socket:  </p>
  
  <pre><code> /opt/lampp/var/mysql/mysql.sock  
  </code></pre>
  
  <p>That file was just there. Today I wanted to keep working on it, and I found that file is not there anymore, so I am getting the following error while I am starting mysql server:  </p>
  
  <pre><code>ERROR 2002 (HY000): 
  Can't connect to local MySQL server through socket 
  '/opt/lampp/var/mysql/mysql.sock' (2)
  </code></pre>
  
  <p>Here are some tests I made:</p>
  
  <pre><code>mujeresponja@ubuntu:~$ ps -fea | grep mysqld
  1000     15707 15615  0 16:28 pts/1    00:00:00 grep --color=auto mysqld
  mujeresponja@ubuntu:~$ ps -fea | grep mysql 
  1000     15709 15615  0 16:29 pts/1    00:00:00 grep --color=auto mysql
  </code></pre>
  
  <p>As a possible solution I uninstalled xampp and reinstall it, and also a new MySQL server, just in case. Anyway, that file is not there anymore.  </p>
  
  <p><strong>EDIT</strong>
  Where the mysql.sock should be, instead there are two files mysql_upgrade_info (Which contains just 5.5.8) and another binary file called ubuntu.err:</p>
  
  <pre><code>mujeresponja@ubuntu:/opt/lampp/var/mysql$ sudo cat ubuntu.err 
  110403 17:28:52 mysqld_safe Starting mysqld daemon with databases from /opt/lampp/var/mysql
  110403 17:28:52 [Note] Plugin 'FEDERATED' is disabled.
  /opt/lampp/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
  110403 17:28:52 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
  InnoDB: The InnoDB memory heap is disabled
  InnoDB: Mutexes and rw_locks use InnoDB's own implementation
  InnoDB: Compressed tables use zlib 1.2.3
  110403 17:28:52  InnoDB: Initializing buffer pool, size = 16.0M
  110403 17:28:52  InnoDB: Completed initialization of buffer pool
  110403 17:28:52  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 /opt/lampp/var/mysql/ibdata1
  InnoDB: File operation call: 'create'.
  InnoDB: Cannot continue operation.
  110403 17:28:52 mysqld_safe mysqld from pid file /opt/lampp/var/mysql/ubuntu.pid ended
  110403 17:29:22 mysqld_safe Starting mysqld daemon with databases from /opt/lampp/var/mysql
  110403 17:29:22 [Note] Plugin 'FEDERATED' is disabled.
  /opt/lampp/sbin/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
  110403 17:29:22 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
  InnoDB: The InnoDB memory heap is disabled
  InnoDB: Mutexes and rw_locks use InnoDB's own implementation
  InnoDB: Compressed tables use zlib 1.2.3
  110403 17:29:22  InnoDB: Initializing buffer pool, size = 16.0M
  110403 17:29:22  InnoDB: Completed initialization of buffer pool
  110403 17:29:22  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 /opt/lampp/var/mysql/ibdata1
  InnoDB: File operation call: 'create'.
  InnoDB: Cannot continue operation.
  110403 17:29:22 mysqld_safe mysqld from pid file /opt/lampp/var/mysql/ubuntu.pid ended
  </code></pre>
  
  <p>(Sorry, I don't know how to show terminal messages in an appropiuate way)
   Can anybody help me on this? Thanks in advance!</p>