How to get a new pid file of Mysql and restart Mysql Successfully? Due to lost of pid file of my server, I can't stop mysql using normal commands like

service mysql stop


which will show

ERROR! MySQL server PID file could not be found!


So I try to stop all mysql processes and restart mysql mannually

I've searched the Internet and found one solution, but it doesn't work for me.

I run

ps aux | grep mysql


and the result shows

root      6490  0.0  0.2 112720  2332 pts/0    S+   03:48   0:00 grep --color=auto mysql


So I type 

kill -9 6490


but the result is

-bash: kill: (6490) - No such process


It seems every time I try to kill it, the pid changes.

How can I really stop all mysql processes? Then be able to get a new pid file? New to linux and mysql, thank you in advance!


Update:

Thanks to Henryk Gerlach's answer, it seems I have shut down all Mysql processes, but after I restart my server the pid file doesn't auto-generate. How should I do to really make my Mysql back to normal??
The result you are showing:

root      6490  0.0  0.2 112720  2332 pts/0    S+   03:48   0:00 grep --color=auto mysql


is actually the pid and process for the  ps aux | grep mysql command. It is not actually a process for MySQL.

A running process for MySQL would look similar to this:

mysql     1894  0.8  9.8 1865804 1192032 ?     Sl   Jul01 300:53 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/DBNAME.err --pid-file=/var/lib/mysql/DBNAME.pid


You can use the command pkill to kill the running MySQL processes by name. However, it's not recommended to kill MySQL in a forceful manner. 

 pkill -f mysql


This will match the filename pattern for any part of the command line

To start/stop the MySQL services, you can run:

service mysqld start 
service mysqld stop 
service mysqld restart


or 

service mysql start
service mysql stop
service mysql restart