An illustrated example of how not to do package updates
I spent a greater part of today discovering how and why
not monitoring our disks on several of our Red Hat Enterprise 5 based
iSCSI backends. The quick summary is that if your
RHEL 5 machine was installed some time ago (or installed recently from
an old installer disk) and upgraded since then,
smartd may not be
monitoring all of your disks; this is all but certain if you've recently
added new disks.
What happened to cause this is a badly considered package update. In
the beginning of RHEL 5, Red Hat's version of the
shipped with an
/etc/smartd.conf and a system that defaulted to
auto-generating the list of disks to monitor every time you started
smartd. Later, RHEL updated
smartmontools and stopped doing this;
instead the new version of
smartd to do the
scan for disks itself. However, applying the update does not re-do
/etc/smartd.conf files, which now have a static list of disks
to monitor that never gets updated. If your list of disks changes after
the package update is applied, you lose.
We normally update our iSCSI backends immediately when they're installed, before we connect them to the enclosure with their data disks. The net result is that several backends were left silently monitoring only the system disks, which is what you could call not desirable.
(The problem does not occur with recent RHEL 5 install images, which
have the updated
smartmontools RPM rolled into the base OS.)
To be blunt, this is a badly done package update, especially for a theoretically 'enterprise' operating system. You should never create a situation where a sysadmin installs a package without changing its configuration files, installs an upgrade, and the package stops working, partly because creating such situations is a great way to persuade sysadmins to never install package updates.
(What RHEL should have done is keep the auto-generation system but
change the default
/etc/smartd.conf to not use it. Then everyone would
have been happy; people with the old configuration would have had it
keep updating their list of disks, and people with the new configuration
would have their disks auto-detected by