After successful installation of oracle database on Linux follow below procedure to autostart the oracle database after server reboot

_{Auto Start Oracle 11g Database on Linux}

Step 1 – Login as root user, edit oratab file and modify the letter N to Y

vi /etc/oratab
ORCL:/u01/app/oracle/product/11.2.0/dbhome_1:Y

Step 2 – Create Init script for autostart and stop service

[root@~]# cd /etc/init.d
[root@init.d]# vi dbora
!/bin/sh
ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_1
ORACLE_OWNER=oracle
case "$1" in
'start') # Start the Oracle databases and listeners
su - $ORACLE_OWNER -c "$ORACLE_HOME/bin/dbstart $ORACLE_HOME"
;;
'stop') # Stop the Oracle databases and listeners
su - $ORACLE_OWNER -c "$ORACLE_HOME/bin/dbshut $ORACLE_HOME"
;;
esac

Step 3 -Add init script created to the run level

[root@ init.d]# 
chgrp dba dbora
chmod 750 dbora
ln -s /etc/init.d/dbora /etc/rc.d/rc0.d/K01dbora
ln -s /etc/init.d/dbora /etc/rc.d/rc3.d/S99dbora
ln -s /etc/init.d/dbora /etc/rc.d/rc5.d/S99dbora

Step 4 – Reboot and test database service and listner service is starting automatically

[oracle@dbbackup]$ ps -ef|grep smon
oracle 13095 1 0 08:49 ? 00:00:00 ora_smon_orcl
[oracle@dbbackup]$ ps -ef|grep tns
oracle 8415 1 0 08:48 ? 00:00:00 /u01/app/oracle/product/11.2.0/dbhome_1/bin/tnslsnr LISTENER -inherit

_{Auto Start Oracle 12c Database on Linux}

mkdir /home/oracle/scripts