[CentOS-virt] What is the purpose setting console=hvc0 in the dom0 grub config?
Konrad Rzeszutek Wilk
konrad.wilk at oracle.com
Wed May 17 15:43:48 UTC 2017
On Wed, May 17, 2017 at 08:37:13AM -0700, Jerry wrote:
> On Wed, May 17, 2017 at 8:25 AM, Konrad Rzeszutek Wilk <
> konrad.wilk at oracle.com> wrote:
> > > This is what's defined in /etc/default/grub following the install of the
> > > Xen:
> > >
> > > GRUB_CMDLINE_XEN_DEFAULT="dom0_mem=1024M,max:1024M cpuinfo
> > com1=115200,8n1
> > > console=com1,tty loglvl=all guest_loglvl=all"
> > > GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT="console=hvc0 earlyprintk=xen
> > > nomodeset"
> > >
> > > I didn't set these myself, this is what the xen package (or one of its
> > > dependencies) is doing.
> > >
> > > I'm still not clear on why hvc0 is needed, or why it's being set, but
> > what
> > > I do know for sure is it was causing the boot messages to be suppressed.
> > So the hvc0 is to use the PV console driver to pipe all the messages to
> > the Xen one.
> > And Xen is configured to use the serial console (com1=115200,8n1).
> > Which means that all you Linux bootup info should be piped to that.
> So how would I properly configure it to still write to tty without
> disabling hvc0? Perhaps something like this?
> GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT="console=hvc0,tty earlyprintk=xen
And that should do it.
> Looks like I have some learning to do. Do you happen to know of a good
> article explaining how console redirection works?
You add the 'console' and it will pipe date to it.
If you add more, then it will duplicate it to those.
> > But Linux is pretty quiet unless you add 'loglevel=10' or 'debug' on the
> > Linux command line.
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