[Qemu-devel] How to get target system display with qemu -nographic option?

[Qemu-devel] How to get target system display with qemu -nographic option?

[Atoosah]

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I would like to run my fedora core image using Qemu in nographic mode.
Currently I am able to get qemu's serial console, but not the login
prompt/"target system display". So, far I am able to the Qemu's serial
console (i.e. the graphical emulations Ctrl-Alt-3 output) if I use the
option -serial pty or -serial vc, but the option -serial stdio does not give
me the (qemu) prompt.

1. Is the system display available, hidden? If so, what options are missing
below to enable this?

2. Do I need to make changes to host? I've tried adding the entry
"7:2345:respawn:/sbin/mgetty ttyS0 9600 vt100-nav" to the /etc/inittab file.
Also, /dev/ttyS0 does exists.

I have tried running qemu with both ways below, which have the same effect.
The append option currently seems to have no effect.
$ qemu -hda mydisk.img -m 512 -append "root=/dev/hda console=ttyS0"
-nographic -serial vc

$ qemu -hda mydisk.img -m 512 -nographic -serial vc

3. Why does qemu just start with the serial output, but does not allow me to
switch to neither the console output nor the target output? i.e. No Ctrl
keys work (Ctrl-a c, Ctrl-a x, ...)

Thank you in advance.

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Re: [Qemu-devel] How to get target system display with qemu -nographic option?

[David Barrett]

When -nographic is specified, no graphical window is created.  The only 
way to see the graphics window is using the VNC option.

Furthermore, when -nographic is specified, I think "-monitor" defaults 
to "serial", meaning the actual serial output is overridden by the qemu 
monitor.  To change this, look at "-monitor" and direct it somewhere 
else (such as to a TCP stream).

Does this help?

-david

Atoosah wrote:
> I would like to run my fedora core image using Qemu in nographic mode. 
> Currently I am able to get qemu's serial console, but not the login 
> prompt/"target system display". So, far I am able to the Qemu's serial 
> console (i.e. the graphical emulations Ctrl-Alt-3 output) if I use the 
> option -serial pty or -serial vc, but the option -serial stdio does not 
> give me the (qemu) prompt.
> 
> 1. Is the system display available, hidden? If so, what options are 
> missing below to enable this?
> 
> 2. Do I need to make changes to host? I've tried adding the entry 
> "7:2345:respawn:/sbin/mgetty ttyS0 9600 vt100-nav" to the /etc/inittab 
> file. Also, /dev/ttyS0 does exists.
> 
> I have tried running qemu with both ways below, which have the same 
> effect. The append option currently seems to have no effect.
> $ qemu -hda mydisk.img -m 512 -append "root=/dev/hda console=ttyS0" 
> -nographic -serial vc
> 
> $ qemu -hda mydisk.img -m 512 -nographic -serial vc
> 
> 3. Why does qemu just start with the serial output, but does not allow 
> me to switch to neither the console output nor the target output? i.e. 
> No Ctrl keys work (Ctrl-a c, Ctrl-a x, ...)
> 
> Thank you in advance.

[Qemu-devel] How to get target system display with qemu -nographic option?

[Atoosah]

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>
> When -nographic is specified, no graphical window is created.  The only
> way to see the graphics window is using the VNC option.
>

If I run the program with graphics enabled (i.e. no -nographic option) I get
the login prompt and then the password. From then on, the display is in
shell prompt mode. So, does -nographic mean that I won't be able to access
this display? If so, it seems very limiting without being able to run
experiments on our guest machine.


>
> Furthermore, when -nographic is specified, I think "-monitor" defaults
> to "serial", meaning the actual serial output is overridden by the qemu
> monitor.  To change this, look at "-monitor" and direct it somewhere
> else (such as to a TCP stream).
>

I'd appreciate if you'd explain a bit more what you mean by "serial output
is overridden by the qemu
monitor"..


>
> Does this help?
>

Thank you. I'm still looking at the vnc option. Just to make sure the
/etc/inittab that is modified (with 7:2345:respawn:/sbin/mgetty ttyS0 9600
vt100-nav) should be the guests or the hosts? I'm a newbie in this area, so
any help would be appreciated.


>
> -david
>

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Re: [Qemu-devel] How to get target system display with qemu -nographic option?

[David Barrett]

Atoosah wrote:
>     When -nographic is specified, no graphical window is created.  The only
>     way to see the graphics window is using the VNC option.
> 
> If I run the program with graphics enabled (i.e. no -nographic option) I 
> get the login prompt and then the password. From then on, the display is 
> in shell prompt mode. So, does -nographic mean that I won't be able to 
> access this display? If so, it seems very limiting without being able to 
> run experiments on our guest machine.

Ah, "graphics" means "display" -- it doesn't matter whether your guest 
VM is running X or using a simple terminal, it all looks like one big 
graphic to qemu.

Said another way, "-nographic" disables the display entirely, whether 
that display is used for graphics or text.


>     Furthermore, when -nographic is specified, I think "-monitor" defaults
>     to "serial", meaning the actual serial output is overridden by the qemu
>     monitor.  To change this, look at "-monitor" and direct it somewhere
>     else (such as to a TCP stream).
> 
> I'd appreciate if you'd explain a bit more what you mean by "serial 
> output is overridden by the qemu
> monitor"..

The "monitor" is the command-line interface to control qemu (start and 
stop the VM, snapshots, etc).  Normally, you can get to it with the 
Control-Alt key combination: the display window switches to a terminal 
showing the qemu monitor.

However, when "-nographic" is specified, there is no display window. 
So, it pretends you specified "-monitor serial", which enables access to 
the qemu monitor via the virtual serial cable.  Unfortunately, that 
means that you can no longer access the *real* virtual serial cable.

So, when you specify -nographic, I think if you just also specify 
"-monitor none" then it'll disable the qemu monitor entirely and leave 
the virtual serial port alone, letting you log on to your VM through the 
virtual serial cable as you expect.


I *think* this is accurate, but I honestly haven't logged on to a qemu 
vm via the serial port before (I just set up SSH), so there's some 
guesswork involved.  Take a look at the documentation for "-serial" and 
"-monitor" and that should shed some light.



>     Does this help?
> 
> 
> Thank you. I'm still looking at the vnc option. Just to make sure the 
> /etc/inittab that is modified (with 7:2345:respawn:/sbin/mgetty ttyS0 
> 9600 vt100-nav) should be the guests or the hosts? I'm a newbie in this 
> area, so any help would be appreciated.

I don't know what you're trying to do with /etc/inittab.  That doesn't 
mean it's wrong, it just means I've never found it necessary to go that 
route.  I'm guessing you should probably undo all your changes there and 
just stick with whatever was the default, and then use the "-nographic 
-monitor none" option I mention above.

-david

Re: [Qemu-devel] How to get target system display with qemu -nographic option?

[andrzej zaborowski]

2008/7/18 Atoosah <atoosaah@gmail.com>:
>
>>
>> When -nographic is specified, no graphical window is created.  The only
>> way to see the graphics window is using the VNC option.
>
> If I run the program with graphics enabled (i.e. no -nographic option) I get
> the login prompt and then the password. From then on, the display is in
> shell prompt mode. So, does -nographic mean that I won't be able to access
> this display? If so, it seems very limiting without being able to run
> experiments on our guest machine.
>
>>
>> Furthermore, when -nographic is specified, I think "-monitor" defaults
>> to "serial", meaning the actual serial output is overridden by the qemu
>> monitor.  To change this, look at "-monitor" and direct it somewhere
>> else (such as to a TCP stream).
>
> I'd appreciate if you'd explain a bit more what you mean by "serial output
> is overridden by the qemu
> monitor"..
>
>>
>> Does this help?
>
> Thank you. I'm still looking at the vnc option. Just to make sure the
> /etc/inittab that is modified (with 7:2345:respawn:/sbin/mgetty ttyS0 9600
> vt100-nav) should be the guests or the hosts? I'm a newbie in this area, so
> any help would be appreciated.

On the guest. When you use -nographic, you get a (vritual) pc without
a monitor, but with a serial port. If your Fedora is not set up to
have a login on the serial port, you will see nothing when you connect
a serial cable to the port. You can have login prompts both on serial
and on screen.

You could also ssh into the guest instead.