install perl DBD::Oracle (Lesson learned: CPAN and yum don't mix)

From the many tales of woe on the web about installing perl DBD::Oracle, from "invalid lvalue in assignment" to mysterious make errors, and the pages of intricate instructions doubtfully translated from the French, I assumed that it was a long and difficult process and it was natural that I was having problems installing on 64-bit CentOS. WRONG! It can actually be easy for lazy and dumb people like me.

First, just use yum and hand-compiling. Don't add CPAN to the mix.

1. Add the rpmforge repo and the EPEL repo (see links for instructions) so that you can install perl-DBD and perl-DBI via yum.
2. Install perl-DBD and perl-DBI via yum.
3. Download and install the OCI client "basic" and "sdk/devel" packages from Oracle. Note that you might need an older version if you're connecting to an older version of Oracle. Note also that Oracle makes you log in to download this. Note also that you need both the SDK and the Basic package. I recommend getting the rpms - install with a simple rpm -Uvh .
4. Oracle puts the libraries in a wacky place, e.g. /usr/lib/oracle/11.2/client64/lib if you're using the 64-bit version of 11.2. Therefore, create a new file, e.g. oci.conf, in /etc/ld.so.conf.d/, with the library location in it, and then run (as root) ldconfig -v to add it.
5. Download the DBD::Oracle source from cpan and extract it someplace. 
6. Set some environment variables:
   

   export ORACLE_HOME=/usr/lib/oracle/11.2/client64
   export PATH=$PATH:$ORACLE_HOME/bin
   export LD_LIBRARY_PATH=$ORACLE_HOME/lib

7. Run "perl Makefile.PL -V 11.2.0" in the directory where the OCI client was extracted. Change the version number to whatever the correct version is. This avoids the "I could not determine Oracle client version so I'll just default to version 8.0.0.0" issue.
8. Run "make install".
9. You should be done!

The latest versions of the Oracle Instant Client default to making incredibly verbose logs in the user's home directories - how to disable default oradiag_user instant client logging.

RHEL 5 - postfix suddenly can't send mail

As described in this RedHat bug, selinux-policy-2.4.6-255.el5_4.3 (1/7/2010) breaks postfix sendmail.

You'll see messages like:

fatal: username(1002): unable to execute /usr/sbin/postdrop -r: Success
postfix/sendmail[19202]: warning: premature end-of-input on /usr/sbin/postdrop -r while reading input attribute name

in /var/log/maillog.

You have a couple of options for dealing with this issue.

1. You can roll back to an earlier policy version and wait for a patched version to come out.
2. You can update the policy manually as described in the bug.
3. You can temporarily change selinux to permissive mode using "echo 0 > /selinux/enforce" until RHEL produces the patch. Then you can switch to enforcing again using "echo 1 > /selinux/enforce".

TIMTOWDI and all that, so perhaps you can think of others.