By relling on Jan 20, 2005
I have been known to rant about /etc/system viruses. These occur when people blindly copy /etc/system tunables to different systems or carry them forward during OS upgrades. FYI, each Solaris release contains a document called the Solaris Tunable Parameters Guide which is intended to document /etc/system (and other) tunables and makes recommendations as to their use. While this has cut down the myths about the tunables, they still have viral characteristics.
In Solaris 10 there is another type of similar conundrum that is similar. I'll call these /etc/vfstab viruses. We do some clever things with Solaris 10 to implement some of the cool new features. Some of these need /etc/vfstab entries, specifically the contract file system (ctfs) and the kernel object file system (objfs). This means that if you install a Solaris 10 system, copy over your old /etc/vfstab (this propagating it like a virus), then you can render your Solaris 10 partially inoperative.
The lesson: you should always review changes to configuration files during OS upgrades, especially /etc/system and /etc/vfstab. Do not simply copy previous versions of these files onto the new OS. If you don't understand what the files are or what should go in them, please take some time to look at the supplied documentation.