DBT-00007 User does not have the appropiate write privilege when starting dbca

At the moment I am preparing some virtualboxes to create the live demos for my presentation about "Single Tenancy is only more complexity!?" at the DOAG Conference 2018.

For this, I have setup a fresh new Linux and installed 18c Grid Infrastructure into it (using role separation, so GI is installed with the grid user, the databases should be installed with the oracle user).

After I have created my 2 ORACLE_HOMEs with the Standard Edition 2 and the Enterprise Edition database (Software only) I wanted to set up the first databases, but unfortunately the dbca (Database configuration assistant) struggled with "a [DBT-00007] User does not have the appropriate write privilege when starting dbca" error. Since I NEVER have seen that error before, I really was wondering, what happens (and I don't think I have missed some steps). And no, I don't want to check this with the Oracle support, like mentioned at the popup window details.

I have setup my ORACLE_BASE and ORACLE_HOME before I have started dbca, so this isn't the cause for this error. As the popup window does not shown anything in addition, I tried to check the log of the dbca at $ORACLE_BASE/cfgtoollogs/dbca - but there wasn't any.
So the problem seemed to by correlated to this directory.

The owner of $ORACLE_BASE/cfgtoollogs was grid (group oinstall) and the rights set were 755 - so only the grid user was allowed to write, group members weren't.

To change this I have first changed the owner of the cfgtoollogs directory:

chown -hR oracle:oinstall /u01/app/oracle/cfgtoollogs
and afterwards I have given write rights to all subdirectories, so also the grid user would still be able to add his stuff to the log directory:

chmod 775 /u01/app/oracle/cfgtoollogs/
chmod 770 /u01/app/oracle/cfgtoollogs/dbca
chmod 770 /u01/app/oracle/cfgtoollogs/asmca
chmod 770 /u01/app/oracle/cfgtoollogs/netca

That's it folks, the dbca started after I have made these changes.