Where can I find mysqld error logs? I am trying to run mysql but I get this errors and I don't know what to do. Are there any more error logs where I can find more information?

/usr/local/mysql/bin# ./mysqld

150321 15:35:20 [ERROR] Can't find messagefile '/usr/share/mysql/english/errmsg.sys'
150321 15:35:20 [Note] Plugin 'FEDERATED' is disabled.
./mysqld: Unknown error 1146
150321 15:35:20 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
150321 15:35:20 InnoDB: The InnoDB memory heap is disabled
150321 15:35:20 InnoDB: Mutexes and rw_locks use GCC atomic builtins
150321 15:35:20 InnoDB: Compressed tables use zlib 1.2.3
150321 15:35:20 InnoDB: Using Linux native AIO
150321 15:35:20 InnoDB: Initializing buffer pool, size = 128.0M
150321 15:35:20 InnoDB: Completed initialization of buffer pool
150321 15:35:20 InnoDB: highest supported file format is Barracuda.
150321 15:35:20  InnoDB: Waiting for the background threads to start
150321 15:35:21 InnoDB: 1.1.5 started; log sequence number 1595675
150321 15:35:21 [ERROR] Aborting

150321 15:35:21  InnoDB: Starting shutdown...
150321 15:35:22  InnoDB: Shutdown completed; log sequence number 1595675
I have no idea how it happened, but:
1) mysqld was not using /etc/mysql/my.cnf file.

2) I could not find any other my.cnf files on the machine.

3) So i changed /etc/mysql/my.cnf to point to my data files

4) And I created a symlink for socket:

ln -s /var/run/mysqld/mysqld.sock /tmp/mysql.sock

5) And then I run the deamon:

/usr/local/mysql/bin/mysqld_safe --defaults-file=/etc/mysql/my.cnf