emerge @preserved-rebuild

After installing an application I get this:

!!! existing preserved libs:
>>> package: sys-fs/udev-197-r4
 *  - /lib/libudev.so.0
 *  - /lib/libudev.so.0.11.5
 *      used by /lib/udev/udev-configure-printer (app-admin/system-config-printer-common-1.3.11-r1)
 *      used by /usr/lib/libatasmart.so.4.0.5 (dev-libs/libatasmart-0.19)
 *      used by /usr/lib/libva-dummy.so.1.3200.0 (x11-libs/libva-1.0.15)
 *      used by 3 other files
Use emerge @preserved-rebuild to rebuild packages using these libraries

So I finally ran: emerge @preserved-rebuild

after rebuilding:
(consolekit-0.4.5_p20120320-r1 , libatasmart-0.19)
I’m getting this:

*   CONFIG_TMPFS_POSIX_ACL:     is not set when it should be.
 * Please check to make sure these options are set correctly.
 * Failure to do so may cause unexpected problems.

How do I fix??

I had a similar question.
See http://www.calculate-linux.org/boards/15/topics/20179

Anyway, you can get this type of a message after an emerge of a package or a tree world upgrade.
Don’t necessarily use my steps below as a How To as I have only done this Twice.
However, might give you a starting point.

So, suppose you
then correct
emerge @preserved-rebuilt
probably a good idea to

After this you should have a message regarding what if any configs to update.
I used tkdiff to compare new and old configs.
_ -3_ is usually a safe choice to merge new and old Or -9 to leave untouched.
I do suggest you read up in the Gentoo Wiki

lastly I recheck sync


Anyone seeing a missed step, Please weigh in.

Update/Upgrade Portage has been a learning experience for me as well.
I have used emerge myself for years installing packages but with Sabayon the Upgrade process with entropy is different and mostly not visible to the user.