In summary, install Oracle Instant Client and try to run sqlplus. If sqlplus connects to the oracle sid then go ahead and install the rails adapters for oracle. What is important to note here, is to install the oracle-instantclient for the architecture of your machine.. I have tested this on Debian Lenny (i386) and CentOS5 (x64)

  1. Download from http://www.oracle.com/technology/software/tech/oci/instantclient/

a. oracle-instantclient-basic-10.2.0.4-1.i386
b. oracle-instantclient-devel-10.2.0.4-1.i386
c. oracle-instantclient-sqlplus-10.2.0.4-1.i386

  1. Unzip everything to /opt/oracle/instantclient . You should have something like the ff:
[root@csapp1 instantclient]# ls -la
total 102704
drwxr-xr-x 3 root root     4096 Dec 10 21:54 .
drwxr-xr-x 3 root root     4096 Dec 10 22:03 ..
-rw-r--r-- 1 root root      228 Dec 10 21:52 BASIC_README
-r--r--r-- 1 root root  1609607 Dec 10 21:52 classes12.jar
-rwxr-xr-x 1 root root    67542 Dec 10 21:52 genezi
-r--r--r-- 1 root root     1525 Dec 10 21:52 glogin.sql
lrwxrwxrwx 1 root root       17 Dec 10 21:54 libclntsh.so -> libclntsh.so.10.1
-rwxr-xr-x 1 root root 21038613 Dec 10 21:52 libclntsh.so.10.1
-r-xr-xr-x 1 root root  3796601 Dec 10 21:52 libnnz10.so
-rwxr-xr-x 1 root root  1664116 Dec 10 21:52 libocci.so.10.1
-rwxr-xr-x 1 root root 72674185 Dec 10 21:52 libociei.so
-r-xr-xr-x 1 root root   138033 Dec 10 21:52 libocijdbc10.so
-r-xr-xr-x 1 root root  1435561 Dec 10 21:52 libsqlplusic.so
-r-xr-xr-x 1 root root   997409 Dec 10 21:52 libsqlplus.so
-r--r--r-- 1 root root  1555682 Dec 10 21:52 ojdbc14.jar
drwxr-xr-x 4 root root     4096 Dec 10 21:52 sdk
-r-xr-xr-x 1 root root     7773 Dec 10 21:52 sqlplus
-rw-r--r-- 1 root root      232 Dec 10 21:52 SQLPLUS_README
-rw-r--r-- 1 root root      516 Dec 10 21:53 tnsnames.ora
[root@csapp1 instantclient]#

  1. Make a symbolic link for libclntsh.so.10.1 as shown above.

  2. Create the Oracle Environment variables

export ORACLE_HOME=/opt/oracle/instantclient
export TNS_ADMIN=$ORACLE_HOME
export LD_LIBRARY_PATH=$ORACLE_HOME:$LD_LIBRARY_PATH
export DYLD_LIBRARY_PATH=$ORACLE_HOME
export PATH=$PATH:$ORACLE_HOME
  1. At this point, you should have oracle-instantclient properly installed. You can test by running sqlplus.
[root@csapp1 instantclient]# sqlplus
 
SQL*Plus: Release 10.2.0.4.0 - Production on Thu Dec 11 11:47:40 2008
 
Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

NOTE: Sometimes you will get a SEGMENTATION FAULT. If so, try to open a new shell with the environment variables loaded and do an sqlplus in a directory which is not /opt/oracle/instantclient.

  1. Install the oracle adapter for rails

  2. gem install ruby-oci8

  3. gem install oracle_enhanced-adapter –source=”http://gems.rubyonrails.org/”

activerecord-oracle-adapter (1.0.0.9250)
activerecord-oracle_enhanced-adapter (1.1.8)

NOTE: Try to look for the latest gems, the source above is at the time of this writing so it might change.

  1. Test using irb
[root@csapp1 instantclient]# irb
irb(main):001:> require 'rubygems'
=> true
irb(main):002:> require 'oci8'
=> true
irb(main):003:>