How to disable QEMU quest-agent channel in UTM 5.0.8?

[aprilffools1411-blip]

For UTM 5.0.8 (build 128), using QEMU ARM64/virt and local SPICE, is there a supported configuration option to prevent generation of the virtserialport named org.qemu.guest_agent.0?

We have disabled clipboard sharing, directory sharing, dynamic resolution and host USB sharing, but the generated QEMU arguments still include the guest-agent channel.

We require a VM for isolated, offline Python testing without host–guest agent communication. We do not want to modify UTM source or use unsupported QEMU argument overrides.

Is disabling this channel supported, and if so, which documented setting should be used?

[vectornguyen76]

Short answer: no, there's no setting for it in UTM 5.0.8.

In Configuration/UTMQemuConfiguration+Arguments.swift (same on the v5.0.8 tag), sharingArguments adds the virtio-serial device and virtserialport,…,name=org.qemu.guest_agent.0 whenever system.architecture.hasAgentSupport && system.target.hasAgentSupport is true. That covers ARM64 + virt. Only the SPICE vdagent part is gated by your sharing options (isSpiceAgentUsed: clipboard sharing, WebDAV directory sharing, dynamic resolution). That's why turning those off removed vdagent, but the guest-agent port stays.

Ways to get the isolation you want without patching UTM or using QEMU argument overrides:

1. Don't run an agent in the guest. The port is just a virtio serial channel; nothing talks over it unless qemu-guest-agent runs inside the VM. For a Debian/Ubuntu guest:

   sudo systemctl disable --now qemu-guest-agent
   sudo apt purge qemu-guest-agent

   (On Windows guests, uninstall the QEMU Guest Agent service.) With no agent, host-to-guest commands over that channel just time out.
2. If you also want the device itself gone, the only options are a feature request ("option to disable guest agent channel"), or the argument override you'd rather avoid.

For an offline Python test VM, option 1, plus removing the network device (Network → None), gives you no host–guest agent communication.