I'm at the linux prompt of a computer running Oracle 11.
Without connecting to the database, how can I determine what is the instance name of the Oracle server running on this box?
If the DB is running, you can look for the pmon process:
ps auxww | grep pmon | grep -v grep
You'll see one
pmon process for each database that is up. For example
YOURDB is the instance name.
You can also ask the listener which services it is serving connections for, with:
(Channeling for a_horse_with_no_name, who left a good answer in a comment.)
In most Linux distributions you can check the instances by looking at
# Entries are of the form: # $ORACLE_SID:$ORACLE_HOME:<N|Y>: orcl:/data/oracle/software:N
if you've installed Oracle with the installer, you can try with this: