What should be done to connect to Oracle DB as SYSDBA?

Question

Oracle

Hello. Guys, please show "on your fingers" how to enter sqlPlus as SYSDBA and start a database instance? I can't get past the ora-01031 error. The database is on Ubuntu.
Thanks in advance!

Answer 1

export ORACLE_SID=<database instance name>
sqlplus / as sysdba
It must be executed from under the user who is in the dba group, or from under the one from under which they were set.
PS Strongly recommend - learn materiel. Start with the guides on the vendor's website.

Answer 2

in the classic example
su - oracle
env | grep ORA_
check that ORACLE_HOME is in the place where your database you want to run
ps -elf | grep ORA
and make sure that the instance is not started
sqlplus / as sysdba
get into the database and read the first lines
should be the word idle
startup
PROFIT +)