Issue in installing oracle 18cxe on ubuntu 18.04

Thanks to alexsander-perusso's answer above, the correct answer for oracle-xe-18c on Ubuntu 16.04 is to edit /etc/init.d/oracle-xe-18c by adding

-J-Doracle.assistants.dbca.validate.ConfigurationParams=false

on the line directly below echo "Configuring Oracle Database $ORACLE_SID." after $PDB_NAME.

Here is what the line looks like after the edit:

$SU -s /bin/bash  $ORACLE_OWNER -c "(echo '$ORACLE_PASSWORD'; echo '$ORACLE_PASSWORD'; echo '$ORACLE_PASSWORD') | $DBCA -silent -createDatabase -gdbName $ORACLE_SID -templateName $TEMPLATE_NAME -characterSet $CHARSET -createAsContainerDatabase $CREATE_AS_CDB -numberOfPDBs $NUMBER_OF_PDBS -pdbName $PDB_NAME -J-Doracle.assistants.dbca.validate.ConfigurationParams=false -sid $ORACLE_SID -emConfiguration DBEXPRESS -emExpressPort $EM_EXPRESS_PORT -J-Doracle.assistants.dbca.validate.DBCredentials=false -sampleSchema true $SQLSCRIPT_CONSTRUCT $DBFILE_CONSTRUCT $MEMORY_CONSTRUCT" 

Reference: http://www.eygle.com/archives/2018/11/oracle_18c_19c_dbt_50000.html

I was following the instructions here: https://tec600.wordpress.com/2017/06/29/oracle-installation-on-ubuntu-16-04/ with changes for 18c XE

Results after the above changes:

$sudo /etc/init.d/oracle-xe-18c configure/bin/df: unrecognized option '--direct'Try '/bin/df --help' for more information.Specify a password to be used for database accounts. Oracle recommends that the password entered should be at least 8 characters in length, contain at least 1 uppercase character, 1 lower case character and 1 digit [0-9]. Note that the same password will be used for SYS, SYSTEM and PDBADMIN accounts:Confirm the password:Configuring Oracle Listener.Listener configuration succeeded.Configuring Oracle Database XE.Enter SYS user password: *******Enter SYSTEM user password: *******Enter PDBADMIN User Password: *********Prepare for db operation7% completeCopying database files29% completeCreating and starting Oracle instance30% complete31% complete34% complete38% complete41% complete43% completeCompleting Database Creation47% complete50% completeCreating Pluggable Databases54% complete71% completeExecuting Post Configuration Actions93% completeRunning Custom Scripts100% completeDatabase creation complete. For details check the logfiles at: /opt/oracle/cfgtoollogs/dbca/XE.Database Information:Global Database Name:XESystem Identifier(SID):XELook at the log file "/opt/oracle/cfgtoollogs/dbca/XE/XE.log" for further details.Connect to Oracle Database using one of the connect strings:     Pluggable database: SERVERNAME:1539/XEPDB1     Multitenant container database: SERVERNAME:1539Use https://localhost:5500/em to access Oracle Enterprise Manager for Oracle Database XE

Basically you need to edit the script file with:

sudo nano /etc/init.d/oracle-xe-18c  

And add the Java class:

-JDoracle.assistants.dbca.validade.ConfigurationParams=false

See: https://www.youtube.com/watch?v=RcZLD2l6WTw