$ su root
$ mkdir /oracleInstall
$ cd /oracleInstall
$ curl -o oracle-database-preinstall-18c-1.0-1.el7.x86_64.rpm https://yum.oracle.com/repo/OracleLinux/OL7/latest/x86_64/getPackage/oracle-database-preinstall-18c-1.0-1.el7.x86_64.rpm
$ yum -y localinstall oracle-database-preinstall-18c-1.0-1.el7.x86_64.rpm
$ wget https://download.oracle.com/otn-pub/otn_software/db-express/oracle-database-xe-18c-1.0-1.x86_64.rpm
$ yum -y localinstall oracle-database-xe-18c-1.0-1.x86_64.rpm
$ /etc/init.d/oracle-xe-18c configure
# Linux 6
$ /etc/init.d/oracle-xe-18c start
$ /etc/init.d/oracle-xe-18c stop
$ /etc/init.d/oracle-xe-18c restart
# Linux 7
$ systemctl start oracle-xe-18c
$ systemctl stop oracle-xe-18c
$ systemctl restart oracle-xe-18c
$ su oracle
# vi ~/.bash_profile
export ORACLE_HOME=/opt/oracle/product/18c/dbhomeXE
export TNS_ADMIN=$ORACLE_HOME/network/admin
export ORACLE_SID=XE
export ORAENV_ASK=NO
export PATH=$PATH:$ORACLE_HOME/bin
## 한글 깨질시 추가
export NLS_LANG=KOREAN_KOREA.AL32UTF8
$ source ~/.bash_profile
$ cd /opt/oracle/product/18c/dbhomeXE/bin/
$ sqlplus "/as sysdba"
$ su root
$ rm -rf /oracleInstall
$ su root
$ ./etc/init.d/oracle-xe-18c/lsnrctl stop
$ ./etc/init.d/oracle-xe-18c/lsnrctl start
$ su oracle
$ sqlplus "/as sysdba"
SQL> SHUTDOWN IMMEDIATE
SQL> STARTUP
SQL> ALTER PLUGGABLE DATABASE ALL OPEN;

sqlplus "/as sysdba"
SQL> ALTER session set "_ORACLE_SCRIPT"=true;
# 유저 생성
SQL> CREATE USER 유저명 IDENTIFIED BY 비밀번호;
# 권한 부여
SQL> GRANT RESOURCE,CONNECT,DBA TO 유저명;
SQL> COMMIT;