ORA-01034: ORACLE not available, ORA-27101: shared memory realm does not exist

I share solution the next error:

ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Process ID: 0
Session ID: 0 Serial number: 0

Steps:

Step 1:

Connect user from linux or unix.

*oracle is my user.

sudo su - oracle

* set your password.

* if you don't remmeber your password change password with the next command.

sudo passwd oracle

Step 2:

Use the lsnrctl command to start service

lsnrctl start

Step 3:

Start database:

dbstart

* Try connect your database.

* if you have the next error: try with the step 4.

Step 4:

* Try to login sysdba user:

sqlplus '/ as sysdba'

Step 5:

* Type startup command:

startup.

* Try connect your database

Check image below with commands:

Great :).

References: https://www.cyberciti.biz/faq/how-do-i-start-oracle-service-in-unix/