fix(qemu): fix terminal mess up in qemu based deployment

[ishaanxgupta]

Description

With QEMU, -nographic doesn’t just “disable graphics”; it also redirects the emulated VGA/serial output to the controlling terminal (stdio) and can multiplex the QEMU monitor/serial on the same stream. That output often contains control characters / escape sequences and QEMU can leave your terminal in a weird state when it exits (so you need reset / stty sane).

Replaced -nographic with:

• display none (or -vga none -display none)
• serial stdio
• monitor none

Related issues

• Fixes Fix terminal mess up in Qemu based deployments #440

LLM usage

N/A

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

[netlify]

✅ Deploy Preview for urunc ready!

Name	Link
🔨 Latest commit	d471664
🔍 Latest deploy log	https://app.netlify.com/projects/urunc/deploys/69935b679d50f400085bcd51
😎 Deploy Preview	https://deploy-preview-459--urunc.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[ishaanxgupta]

as per discussion in #440 (comment)
@cmainas please have a look

[spline2hg]

Hi @ishaanxgupta, thanks for working on this.
Would it be possible to add screen recordings showing the behavior before and after the change?
That would make the change easier to understand.

Also, u need to format the code with go fmt.

[ishaanxgupta]

Sure @spline2hg

[ishaanxgupta]

@cmainas please have a look, the tests should pass this time

[cmainas]

Hello @ishaanxgupta ,

you will need to rebase over urunc's main branch so we can merge this.

[cmainas]

Hello @ishaanxgupta ,

it seems there is an issue with docker. For example:

$ sudo docker run --rm -it --runtime io.containerd.urunc.v2 harbor.nbfc.io/nubificus/urunc/redis-qemu-linux-raw:latest
Unable to find image 'harbor.nbfc.io/nubificus/urunc/redis-qemu-linux-raw:latest' locally
latest: Pulling from nubificus/urunc/redis-qemu-linux-raw
f18232174bc9: Pull complete 
9826632aa5dd: Pull complete 
2e7279224f08: Pull complete 
b782747b1d52: Pull complete 
878a56611471: Pull complete 
4f4fb700ef54: Pull complete 
64136cebabc3: Pull complete 
3eab733900b0: Pull complete 
e3a1471f3424: Pull complete 
2d0ac744b2c2: Pull complete 
Digest: sha256:2b350986ba047f80fca90f28868c0d3c5f290f7b1922e67a5fddcb7438dac72e
Status: Downloaded newer image for harbor.nbfc.io/nubificus/urunc/redis-qemu-linux-raw:latest
[2026-02-16T18:18:01Z INFO  virtiofsd] Waiting for vhost-user socket connection...
[2026-02-16T18:18:01Z INFO  virtiofsd] Client connected, servicing requests
qemu-system-x86_64: -serial stdio: cannot use stdio by multiple character devices
qemu-system-x86_64: -serial stdio: could not connect serial device to character backend 'stdio'
[2026-02-16T18:18:01Z INFO  virtiofsd] Client disconnected, shutting down

[ishaanxgupta]

@cmainas sorry, the issue is a duplicate -serial stdio flag. This PR changed qemu.go from -nographic to -display none -vga none -serial stdio -monitor null, but linux.go - MonitorCli() also appends -serial stdio -nodefaults as extra args. QEMU rejects two character devices bound to the same stdio backend.

[cmainas]

@cmainas sorry, the issue is a duplicate -serial stdio flag. This PR changed qemu.go from -nographic to -display none -vga none -serial stdio -monitor null, but linux.go - MonitorCli() also appends -serial stdio -nodefaults as extra args. QEMU rejects two character devices bound to the same stdio backend.

Yeah that is totally correct. You can remove it from Linux then.

[cmainas]

Also, please squash your commits.