rhgb boot -> monitor losing signal (sometimes)

[Adam Jackson]

On Sun, 2011-10-09 at 17:26 +0200, Michael Schwendt wrote:

> Shortly before the Plymouth LUKS passphrase prompt, the screen turns black,
> the monitor reports "No signal" and enters power-saving mode. The system
> hasn't crashed, because instead of pressing Ctrl+Alt+Del I can also enter
> the passphrase blindly for the boot procedure to continue. However,
> nothing "wakes up" the monitor afterwards. Switching to a virtual console
> causes the signal to return, and what is displayed on the screen is not
> GDM but the gray background with the central animation having reached
> 100% or nearly that. There is no virtual console available, and one cannot
> return to GDM either.

Plymouth is just a KMS client like the X server.  Normally it tries to
avoid setting a video mode if it can (so boot flickers less) but it will
do in some cases.  So this sounds like it's a bug in the kernel driver.

Much of the info from the Xorg debugging guide:

http://fedoraproject.org/wiki/How_to_debug_Xorg_problems

is relevant here, although obviously the X log and etc aren't.  In
addition, booting with "plymouth:debug" on the kernel command line will
dump debugging output to /var/log/plymouth-debug.log, which should show
the mode setup that plymouth is trying for.  Boot with that flag set
once, then either boot again without plymouth.debug or rhgb set, or
simply ssh into the machine and copy the log file aside.

- ajax
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