Two different MYSQl instances on same machine? I have MySQL 5.6 installed (Linux). 

/var/lib/mysql
/etc/my.cnf


I have a cold backup that I am recovering:

/var/lib/mysql_backup
/etc/mybackup.cnf


In April I was able to get the backup started and it had been running fine until I had to reboot my machine 2 days ago to release an unmount that wouldn't succeed.

Now, I attempt to restart that second instance and I get an error that doesn't make sense given that it was working for nearly 6 months nonstop before and simultaneous/in parallel with the other instance.

root@VENUS:/var/lib/mysql_backup# mysqld --defaults-file=/etc/mysql/mybackup.cnf --pid-file=/var/run/mysqld/mysqld_backup.pid
2013-10-19 15:48:07 22026 [Note] Plugin 'FEDERATED' is disabled.
mysqld: Can't find file: 'plugin' (errno: 2 - No such file or directory)
2013-10-19 15:48:07 22026 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
2013-10-19 15:48:07 22026 [Note] InnoDB: The InnoDB memory heap is disabled
2013-10-19 15:48:07 22026 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2013-10-19 15:48:07 22026 [Note] InnoDB: Compressed tables use zlib 1.2.3
2013-10-19 15:48:07 22026 [Note] InnoDB: CPU does not support crc32 instructions
2013-10-19 15:48:07 22026 [Note] InnoDB: Using Linux native AIO
2013-10-19 15:48:07 22026 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2013-10-19 15:48:07 22026 [Note] InnoDB: Completed initialization of buffer pool
2013-10-19 15:48:07 22026 [Note] InnoDB: Highest supported file format is Barracuda.
2013-10-19 15:48:07 22026 [Note] InnoDB: 128 rollback segment(s) are active.
2013-10-19 15:48:07 22026 [Note] InnoDB: Waiting for purge to start
2013-10-19 15:48:07 22026 [Note] InnoDB: 1.2.10 started; log sequence number 1642375387
2013-10-19 15:48:07 22026 [Note] Recovering after a crash using /var/log/mysql_backup/mysql-bin
2013-10-19 15:48:07 22026 [Note] Starting crash recovery...
2013-10-19 15:48:07 22026 [Note] Crash recovery finished.
2013-10-19 15:48:07 22026 [Note] Server hostname (bind-address): '192.168.1.70'; port: 3310
2013-10-19 15:48:07 22026 [Note]   - '192.168.1.70' resolves to '192.168.1.70';
2013-10-19 15:48:07 22026 [Note] Server socket created on IP: '192.168.1.70'.
2013-10-19 15:48:07 22026 [ERROR] Fatal error: Can't open and lock privilege tables: Can't find file: 'user' (errno: 2 - No such file or directory)


What am I missing here? Nothing has change from the first time it was running.
Since I am doing partial recovery on a damaged database (I did an iso image cold backup, but did not give the iso maker the proper options and ended up with DOS 8.1 filenames, when they should have been Joliet Long names) I must have previously used the option --skip-grant .

i used the command 
    mysqld_safe --defaults-file=/etc/mysql/mybackup.cnf --skip-grant
and the database started up fine.

Now to continue recovering what I can.