Oracle 11g/12c automatically start /stop on Linux  after server reboot 

cat /etc/oratab

#

# This file is used by ORACLE utilities.  It is created by root.sh

# and updated by either Database Configuration Assistant while creating

# a database or ASM Configuration Assistant while creating ASM instance.

# A colon, ':', is used as the field terminator.  A new line terminates

# the entry.  Lines beginning with a pound sign, '#', are comments.

#

# Entries are of the form:

#   $ORACLE_SID:$ORACLE_HOME:<N|Y>:

#

# The first and second fields are the system identifier and home

# directory of the database respectively.  The third field indicates

# to the dbstart utility that the database should , "Y", or should not,

# "N", be brought up at system boot time.

#

# Multiple entries with the same $ORACLE_SID are not allowed.

#

#

ORAL12:/u01/app/oracle/product/12.1.0/db_1:Y   <<<<<-- for autostart set to Y

create following file on this dir as oracle  

[oracle@ora12c scripts]$ pwd

/home/oracle/scripts

[oracle@ora12c scripts]$ ls -ltr

total 8

-rwxr--r--. 1 oracle oinstall 266 May 21 19:52 ora_start.sh

-rwxr--r--. 1 oracle oinstall 261 May 21 19:53 ora_stop.sh

[oracle@ora12c scripts]$ cat ora_start.sh

#!/bin/bash

# script to start the Oracle database, listener and dbconsole

. ~/.bash_profile

# start the listener and the database

$ORACLE_HOME/bin/dbstart $ORACLE_HOME

# start the Enterprise Manager db console --- Change based on your requirement 

#$ORACLE_HOME/bin/emctl start dbconsole

exit 0

[oracle@ora12c scripts]$ cat ora_stop.sh

#!/bin/bash

# script to stop the Oracle database, listener and dbconsole

. ~/.bash_profile

# stop the Enterprise Manager db console   --- Change based on your requirement 

# $ORACLE_HOME/bin/emctl stop dbconsole

# stop the listener and the database

#$ORACLE_HOME/bin/dbshut $ORACLE_HOME

exit 0

give execute rights to the scripts:

chmod u+x ora_start.sh ora_stop.sh

create this file as root !!!

create "oracle" file in  /etc/init.d/

[root@ora12c ~]# cat  /etc/init.d/oracle

#!/bin/bash

# chkconfig: 345 99 10

# description: Oracle auto start-stop script.

# Set ORA_OWNER to the user id of the owner of the

# Oracle database in ORA_HOME.

ORA_OWNER=oracle

RETVAL=0

case "$1" in

    'start')

        # Start the Oracle databases:

        # The following command assumes that the oracle login

        # will not prompt the user for any values

        su - $ORA_OWNER -c "/home/oracle/scripts/ora_start.sh"

        touch /var/lock/subsys/oracle

        ;;

    'stop')

        # Stop the Oracle databases:

        # The following command assumes that the oracle login

        # will not prompt the user for any values

        su - $ORA_OWNER -c "/home/oracle/scripts/ora_stop.sh"

        rm -f /var/lock/subsys/oracle

        ;;

    *)

        echo $"Usage: $0 {start|stop}"

        RETVAL=1

esac

exit $RETVAL

as root 

chmod 750 /etc/init.d/oracle

then as a root add service 

chkconfig --add oracle

[root@ora12c ~]# chkconfig --list|grep -i oracle

oracle          0:off   1:off   2:off   3:on    4:on    5:on    6:off

chkconfig --list | grep '3:on\|4:on\|5:on'  |awk '{print $1}' | sort

Then check start and stop as a root 

[root@ora12c ~]# service oracle start

Processing Database instance "ORAL12": log file /u01/app/oracle/product/12.1.0/db_1/startup.log

ps -ef|egrep -i 'tns|smon'

oracle    9981     1  0 11:46 ?        00:00:00 /u01/app/oracle/product/12.1.0/db_1/bin/tnslsnr LISTENER -inherit

oracle   10102     1  0 11:46 ?        00:00:00 ora_smon_ORAL12

root     10435  7926  0 11:53 pts/1    00:00:00 grep -E -i tns|smon

service oracle stop

Processing Database instance "ORAL12": log file /u01/app/oracle/product/12.1.0/db_1/shutdown.log

now checking  on reboot

[root@ora12c ~]# init 6 ;

[root@ora12c ~]# ps -ef|egrep -i 'tns|smon'

root        15     2  0 12:47 ?        00:00:00 [netns]

oracle    4191     1  1 12:48 ?        00:00:01 /u01/app/oracle/product/12.1.0/db_1/bin/tnslsnr LISTENER -inherit

oracle    4341     1  0 12:49 ?        00:00:00 ora_smon_ORAL12

root      4603  4283  0 12:50 pts/1    00:00:00 grep -E -i tns|smon

listener.ora File

LISTENER=

  (DESCRIPTION=

    (ADDRESS_LIST=

      (ADDRESS=(PROTOCOL=tcp)(HOST=192.XXX.0.36)(PORT=1521))

      (ADDRESS=(PROTOCOL=ipc)(KEY=extproc))))

SID_LIST_LISTENER=

  (SID_LIST=

    (SID_DESC=

      (GLOBAL_DBNAME=ORAL12)

      (ORACLE_HOME=/u01/app/oracle/product/12.1.0/db_1)

      (SID_NAME=ORAL12))

    (SID_DESC=

      (SID_NAME=plsextproc)

      (ORACLE_HOME=/u01/app/oracle/product/12.1.0/db_1)

      (PROGRAM=extproc)))

=======

or

[root@vbgeneric init.d]# pwd

/etc/init.d

[root@vbgeneric init.d]# ls -ltr oracle

-rwxr-xr-x 1 root root 1957 Jun  2  2016 oracle

 cat oracle

#!/bin/sh

#

# chkconfig: 2345 99 99

#

export ORACLE_BASE=/u01/app/oracle

export ORACLE_HOME=$ORACLE_BASE/product/12.1.0.2/db_1

export ORACLE_HOME_LISTENER=$ORACLE_HOME

export LD_LIBRARY_PATH=$ORACLE_HOME/lib

#export JAVA_HOME=$ORACLE_HOME/jdk

export PATH=$PATH:$ORACLE_HOME/bin:$JAVA_HOME/bin

export ORACLE_SID=orcl12c

#export ORACLE_TRACE=Y

export PATH=$JAVA_HOME/bin:$ORACLE_HOME/bin:$PATH

# Source function library.

. /etc/rc.d/init.d/functions

# See how we were called.

case "$1" in

  start)

        echo "1" > /proc/sys/net/ipv4/ip_forward

        # Route 80 -> 8888 for XDB

        iptables -t nat -A PREROUTING -m tcp  -p tcp --dport 80 -j REDIRECT --to-port 8888

        iptables -t nat -A PREROUTING -m tcp  -p tcp --dport 21 -j REDIRECT --to-port 2121

        su  oracle -c "$ORACLE_HOME/bin/lsnrctl start"

        su  oracle -c "$ORACLE_HOME/bin/dbstart $ORACLE_HOME"

        su  oracle -c "echo alter pluggable database all open';'|$ORACLE_HOME/bin/sqlplus / as sysdba"

        su  oracle -c "/home/oracle/bin/ords.sh start /home/oracle/ords/ords.war"

        ;;

  stop)

        su  oracle -c "$ORACLE_HOME/bin/dbshut $ORACLE_HOME"

        su  oracle -c "$ORACLE_HOME/bin/lsnrctl stop"

        su  oracle -c "/home/oracle/bin/ords.sh stop /home/oracle/ords/ords.war"

        ;;

  restart|reload)

        su  oracle -c "$ORACLE_HOME/bin/dbshut $ORACLE_HOME"

        su  oracle -c "$ORACLE_HOME/bin/lsnrctl stop"

        su  oracle -c "/home/oracle/bin/ords.sh stop /home/oracle/ords/ords.war"

        su  oracle -c "$ORACLE_HOME/bin/lsnrctl start"

        su  oracle -c "$ORACLE_HOME/bin/dbstart $ORACLE_HOME"

        su  oracle -c "echo alter pluggable database all open';'|$ORACLE_HOME/bin/sqlplus / as sysdba"

        su  oracle -c "/home/oracle/bin/ords.sh start /home/oracle/ords/ords.war"

        ;;

  status)

        $ORACLE_HOME/bin/lsnrctl status

        ;;

  *)

        echo $"Usage: $0 {start|stop|restart|reload}"

        exit 1

esac

exit 0