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Re: rhgb and video drivers [was kernel-2.6.11-1.14_FC3 kernel and new nvidia driver]



John DeDourek wrote:

Eric Tanguy wrote:

After that the things went worse and worse. In rhgb mode the system
hanged just after the devices initialization and without rhgb the system
hanged at swap activation. No mean to boot.

[clip...]


I am NOT expert in this and am trying to learn how things work by reading this group,
reading bugzilla, etc. I have been following a bit of a discussion on the rhgb thing, and
will try to summarize:


The rhgb thing was introduced to show a "prettier" view while booting, perhaps thus being
less intimidating to non-technical users. Probably a good thing to increase "market share"
of Linux vs. some of those "other" OS's geared to the vast majority of users (who are
NOT intending to become highly computer literate; but introduction to Linux may
change that...sorry, editorial comment...).


Apparently the rhgb provides the pretty image by firing up an X server early in the boot
process, or in any case switching to graphical mode on the display adapter. However,
the "full desktop" can't be introduced that early in the boot process. If using the default
login style (known as run level 5) then at some point the "early X server" must be shut
down and the "real X server" fired up during the boot process. Prior to FC3, it was
done in the order just stated, i.e. stop X, start X. Unfortunately, this leaves a fraction
of a second where the display has gone from graphical mode to text mode and then
back to graphical mode, causing an annoying flicker in the screen.


Apparently, starting with FC3 (or some update of it), the order was reversed. The
"early X server" is started on one "virtual console". Then later in the boot process,
the "real X server" is started on another "virtual console". Then the screen is switched
from the early to the late console; this results in very little flicker because both of these
consoles are in graphical mode. Then the "early X server" is stopped.


This, unfortunately results in a brief period when two graphical mode X servers are
running in parallel on separate virtual consoles. Apparently this is no problem for
some video card drivers. On the other hand, some programmers of video card
drivers never considered that the driver might be called on to maintain two virtual
consoles simultaneously.


Two workarounds appear for those having trouble with the video card driver handling
the new rhgb scheme:
-- edit grub.conf to remove the rhgb and live with the "technical output" during boot
-- change to using a text mode login (i.e. boot to run level 3); login in text mode and
type "startx" if you want to use graphical mode. (Is there an official way to change
the boot run level after installation?)


So that's my summary of the problem about rhgb as I understand it. I would
appreciate any corrections to the above posted as a followup. (Note that the
original poster had a further problem after eliminating the rhgb. I don't have any
insight into that one.) I hope that the above might be useful to others.


John D.


This is a pretty good summary of the current status of rhgb . It is planned to be removed for FC4 and start the GNOME display manager (Login screen) early. Here is the bugzilla URL for more details and discussions


https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=151952

regards
Rahul


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