Re: qemu: How to detach / reattach to console in -nographic mode?

[Ottavio Caruso <ottavio2006-usenet2012%yahoo.com@localhost>]

On 13/11/2020 03:12, Mayuresh wrote:
> I am looking for something like tmux/screen to attach and detach from qemu
> guest's console (not qemu's console) when qemu is started in -nographic
> mode.
>
> Well I can use tmux/screen itself to keep one dedicated terminal, but
> that's the last resort.
>
> I tried adding a telnet monitor, but it gives me qemu console, not the
> guest OS console. (Can I switch to OS console from qemu console?)
>
> Also quitting from qemu console kills the guest. Is there way to just
> detach leaving the guest running?
>
> Also the CLI options given here [1] for graphics support do not work for
> me when running an armv7 guest. vnc session comes up but hangs during the
> boot. Instead of these options, if I just add a telnet monitor vnc session
> works fine. Don't know the relation between the two, it looks strange to
> me.
>
> [1] http://wiki.netbsd.org/ports/evbarm/qemu_arm/

I am not sure if this is what you want, and I haven't tried it on an arm 
guest, but this is how I launch my NetBSD 9.0 x86_64 guest:

qemu-system-x86_64 \
-drive if=virtio,file=/home/oc/VM/img/netbsd.image,index=0,media=disk \
-M q35,accel=kvm -m 250M -cpu host -smp $(nproc) \
-nic user,hostfwd=tcp:127.0.0.1:5555-:22,model=virtio-net-pci,ipv6=off  \
-daemonize -display none  -vga none \
-serial mon:telnet:127.0.0.1:6665,server,nowait \
-pidfile /home/oc/VM/pid/netbsd-pid \

telnet 127.0.0.1 6665


When I telnet to port 6665, I get the OS serial console and I can switch 
to the qemu serial console by pressing CRTL-C CTRL-A. Killing the 
session doesn't kill the guest. This assumes you have installed the 
serial bootblocks. I'm not sure how this fits into the arm ecosystem, 
though.

There are also security implications. The qemu docs mention using unix 
domain sockets instead of telnet.


--
Ottavio Caruso