mysql@darkstar:/usr/local/mysql/libexec$ ./mysqld
080916 21:44:51 [Warning] option 'max_join_size': unsigned value 18446744073709551615 adjusted to 4294967295
080916 21:44:51 [Warning] option 'max_join_size': unsigned value 18446744073709551615 adjusted to 4294967295
080916 21:44:51 InnoDB: Started; log sequence number 0 43655
080916 21:44:51 [ERROR] Can't start server : Bind on unix socket: Permission denied
080916 21:44:51 [ERROR] Do you already have another mysqld server running on socket: /var/run/mysql/mysql.sock ?
080916 21:44:51 [ERROR] Aborting

080916 21:44:51 InnoDB: Starting shutdown...
080916 21:44:52 InnoDB: Shutdown completed; log sequence number 0 43655
080916 21:44:52 [Note] ./mysqld: Shutdown complete

mysql@darkstar:/usr/local/mysql/libexec$

??

Sure you don't have another instance of mysqld running? Do you have permission to create a file of that name for the UNIX socket?

what does ps -ef | grep mysql give you? This lists your currently running processes, so look at that and see if you have two instances of mysql running.

how can i create it ? im new on linux

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mysql@darkstar:/usr/local/mysql/libexec$ ps -ef |grep mysql
mysql 3740 3736 0 14:00 pts/3 00:00:00 sh
mysql 3744 3740 0 14:00 pts/3 00:00:00 ps -ef
mysql 3745 3740 0 14:00 pts/3 00:00:00 grep mysql
mysql@darkstar:/usr/local/mysql/libexec$
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What does ls -l /var/run/mysql/mysql.sock give you? Also, ls -ld /var/run/mysql. MySQL will create the socket for you, if the user starting MySQL has the necessary permissions.