Today I installed (again) Oracle XE on Debian (Lenny) and got the following error:
ORA-01034: ORACLE not available ORA-27123: unable to attach to shared memory segment SVR4 Error: 13: Permission denied
I suspected problem was caused by errant ORACLE_HOME / ORACLE_SID values bug got the answer:
chmod 6751 $ORACLE_HOME/bin/oracle
That gives "
-rwsr-s--x". Why permissions were not set properly on installation – have no idea. Any clues?