This is an old, old bug that I just tripped over for the second time. Hopefully this'll save someone else...
In September 2010, I had a problem with Ocsinventory, the inventory software we use to track hour hardware: I kept getting 500 errors when running the OCS client on a machine. I filed a bug, but I wanted to show how I tracked it down.
First off, Apache logs for Ocs can be found at
/var/log/httpd/access_log and /var/log/httpd/error_log. Ocs itself
logs at /var/log/ocsinventory-server (-client too, but that's not as
interesting). However, by default Ocs doesn't log very much -- so
let's change that. Logging can be twiddled by editing the Ocs/Apache
config file at /etc/httpd/conf.d/ocsinventory-server.conf. Pay
attention to this setting: PerlSetEnv OCS_OPT_DBI_PRINT_ERROR. It's
set to 0 by default, so set it to 1 to turn it on. Also, note that
you have to fully restart Apache in order to make changes to this
file take effect
After that, I see this error in /var/log/httpd/error_log:
DBD::mysql::db do failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '|CHECKSUM|1),
NAME='server23',
WORKGROUP='example.com',
USERDOMAIN=NU' at line 4 at/usr/lib/perl5/vendor_perl/5.8.8/Apache/Ocsinventory/Server/Inventory/Update/Hardware.pm line 35.
So the fix? Edit Hardware.pm and look for these lines at the top:
package Apache::Ocsinventory::Server::Inventory::Update::Hardware;
use strict;
require Exporter;
our @ISA = qw /Exporter/;
our @EXPORT = qw / _hardware /;
use Apache::Ocsinventory::Server::Constants;
use Apache::Ocsinventory::Server::System qw / :server /;
Add this line right afterward:
use constant CHECKSUM_MAX_VALUE => 262143;
and restart Apache. After that, I see this in httpd/error_log:
Constant subroutine Apache::Ocsinventory::Server::Inventory::Update::Hardware::CHECKSUM_MAX_VALUE redefined at /usr/lib/perl5/5.8.8/constant.pm line 103.
However, it doesn't appear to affect things, and I can now run the client on the machine. Bletcherous hack, but it gets the job done.