MySQL Cluster - mysql api nodes are failing to start

I am trying to start mysqld(API) nodes as a part of my mysql cluster setup and now it is always failing to start with below error -

Command used to start mysql API is -

 mysqld &

Error that I am getting -

2015-12-14 11:58:26 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2015-12-14 11:58:27 26964 [Note] Plugin 'FEDERATED' is disabled.
2015-12-14 11:58:27 26964 [Note] InnoDB: Using atomics to ref count buffer pool pages
2015-12-14 11:58:27 26964 [Note] InnoDB: The InnoDB memory heap is disabled
2015-12-14 11:58:27 26964 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2015-12-14 11:58:27 26964 [Note] InnoDB: Memory barrier is not used
2015-12-14 11:58:27 26964 [Note] InnoDB: Compressed tables use zlib 1.2.3
2015-12-14 11:58:27 26964 [Note] InnoDB: Using Linux native AIO
2015-12-14 11:58:27 26964 [Note] InnoDB: Not using CPU crc32 instructions
2015-12-14 11:58:27 26964 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2015-12-14 11:58:28 26964 [Note] InnoDB: Completed initialization of buffer pool
2015-12-14 11:58:28 26964 [Note] InnoDB: Highest supported file format is Barracuda.
2015-12-14 11:58:28 26964 [Note] InnoDB: The log sequence numbers 5061242 and 5061242 in ibdata files do not match the log sequence number 5572962 in the ib_logfiles!
2015-12-14 11:58:28 26964 [Note] InnoDB: Database was not shutdown normally!
2015-12-14 11:58:28 26964 [Note] InnoDB: Starting crash recovery.
2015-12-14 11:58:28 26964 [Note] InnoDB: Reading tablespace information from the .ibd files...
2015-12-14 11:58:28 26964 [Note] InnoDB: Restoring possible half-written data pages
2015-12-14 11:58:28 26964 [Note] InnoDB: from the doublewrite buffer...
2015-12-14 11:58:29 26964 [Note] InnoDB: 128 rollback segment(s) are active.
2015-12-14 11:58:29 26964 [Note] InnoDB: Waiting for purge to start
2015-12-14 11:58:29 26964 [Note] InnoDB: 5.6.23 started; log sequence number 5572962
2015-12-14 11:58:29 26964 [Note] NDB: Changed global value of binlog_format from STATEMENT to MIXED
2015-12-14 11:58:30 26964 [Note] NDB: NodeID is 51, management server '10.55.14.153:1186'
2015-12-14 11:58:59 26964 [Note] NDB[0]: NodeID: 51, some storage nodes connected
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Starting...
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Started
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Setting up
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Created schema Ndb object, reference: 0x80040033, name: 'Ndb Binlog schema change monitoring'
2015-12-14 11:58:59 26964 [Note] NDB Util: Starting...
2015-12-14 11:58:59 26964 [Note] NDB Util: Wait for server start completed
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Created injector Ndb object, reference: 0x80050033, name: 'Ndb Binlog data change monitoring'
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Setup completed
2015-12-14 11:58:59 26964 [Note] NDB Binlog: Wait for server start completed
2015-12-14 11:58:59 26964 [Note] NDB Index Stat: Starting...
2015-12-14 11:58:59 26964 [Note] NDB Index Stat: Wait for server start completed
2015-12-14 11:58:59 26964 [Note] RSA private key file not found: /var/lib/mysql//private_key.pem. Some authentication plugins will not work.
2015-12-14 11:58:59 26964 [Note] RSA public key file not found: /var/lib/mysql//public_key.pem. Some authentication plugins will not work.
2015-12-14 11:58:59 26964 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
2015-12-14 11:58:59 26964 [Note]   - '0.0.0.0' resolves to '0.0.0.0';
2015-12-14 11:58:59 26964 [Note] Server socket created on IP: '0.0.0.0'.
2015-12-14 11:58:59 26964 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.user' doesn't exist

Can anyone please tell me what is the problem here ?

Do I have to perform below steps?

https://dev.mysql.com/doc/mysql-security-excerpt/5.6/en/sha256-authentication-plugin.html

Thanks,

Possibly already answered here

Also, like @R.M.D said, you should start mysql as a service.