MySQL startup script only works if you have installed MySQL server using binary method such as apt-get, rpm command or up2date/yum tools etc.
All you need to do is use mysqld_safe command to start the mysqld daemon on Unix or Linux oses. So to start MySQL just type following command:
# /usr/bin/mysqld_safe &
Usually mysqld_safe located at /usr/bin/ directory. However, if you custom compiled MySQL then it will be available in your custom directory (specified using â€“prefix=/path/to/dir option to ./configure command). For example if you installed MySQL in /server/mysql directory then you need to pass this option to mysqld_safe command:
# /usr/bin/mysqld_safe --basedir=/server/mysql --datadir=/data/mysql --log=/var/log/mysql.log &
Read man page of mysqld_safe for more information.