Well, still don't know what it means. However, to get it to go away, I followed the instructions here and added the option nomodeset
to grub. Now those errors are gone as well as a few other things which I thought looked odd, like:
vga16fb: not registering due to another framebuffer present
and others. Hope this helps others... I'm not going to award myself the answer. If someone could explain this error, and (?perhaps?) how it's related to Xorg's compositing, then I'll happily award points (or bounties -- if I ever get enough points to do so). ~ m
Please note, that I did at a minimum add the Xorg extension to disable compositing and this only made one of the five lines which read composite sync not supported
go away. So I undid this change and kept searching until I found the above grub option which removed all of the errors.
For what I can understand it means that a query from the Bios/Firmware related to the ACPI (If you are running a laptop it means the battery, if you are running a Desktop PC it means a UPS or similar) is not recognized.
What Ubuntu did there was ignore the query to not cause problems. Some of the stuff you might see because of this are:
Ubuntu battery state does not detect when the battery has been disconnected. Showing you still the same "Battery Connected" symbol.
Battery charging notification is not updated correctly.
This does not mean the battery will not charge correctly, or that it did not detect the state of the battery correctly, it just means that in the Desktop you will not see it correctly. This does not even mean it will not show correctly to you.
For performance related stuff, you will not suffer any performance problems. It will be running the same as always.
Basically this comes from a BIOS, first assuming that the OS is Windows and then doing a query to it to confirm some information.
Anyway don't worry about it, Ubuntu and any other Linux distro can effectively just tell the BIOS that it is in fact Windows and get the correct query from it. Dmesg and the booting system just post that message there to notify you about the BIOS asking something to the OS (Remember, it is assuming is Windows) and Linux trying to fake it so the BIOS sends the complete query. This is a reason why BIOS manufacturers should not assume that the only hardware they will work on is Windows.
Best Answer
Usually
kernel
's operation related messages are stored in a fixed sized memory called theKernel Ring Buffer
. It's location is/proc/kmsg
.dmesg
usually prints the entries of theKernel Ring Buffer
in a human readable format. As it is a buffer (a temporary storage) mounted under/proc
, you can imagine that it will not survive a reboot i.e. it will just show all the Kernel logs after being powered On. If you want to check all the previous Kernel logs you need to check/var/log/kern.log
, as it is being stored on the disk it will survive the reboots.