pveversion -v
qm config VMID
(VMID of your opnsense)root@pve:~# pveversion -v proxmox-ve: 7.1-1 (running kernel: 5.15.19-2-pve) pve-manager: 7.1-10 (running version: 7.1-10/6ddebafe) pve-kernel-helper: 7.1-12 pve-kernel-5.15: 7.1-11 pve-kernel-5.13: 7.1-8 pve-kernel-5.15.19-2-pve: 5.15.19-2 pve-kernel-5.13.19-5-pve: 5.13.19-10 pve-kernel-5.13.19-4-pve: 5.13.19-9 ceph: 15.2.15-pve1 ceph-fuse: 15.2.15-pve1 corosync: 3.1.5-pve2 criu: 3.15-1+pve-1 glusterfs-client: 9.2-1 ifupdown: residual config ifupdown2: 3.1.0-1+pmx3 ksm-control-daemon: 1.4-1 libjs-extjs: 7.0.0-1 libknet1: 1.22-pve2 libproxmox-acme-perl: 1.4.1 libproxmox-backup-qemu0: 1.2.0-1 libpve-access-control: 7.1-6 libpve-apiclient-perl: 3.2-1 libpve-common-perl: 7.1-3 libpve-guest-common-perl: 4.1-1 libpve-http-server-perl: 4.1-1 libpve-network-perl: 0.7.0 libpve-storage-perl: 7.1-1 libqb0: 1.0.5-1 libspice-server1: 0.14.3-2.1 lvm2: 2.03.11-2.1 lxc-pve: 4.0.11-1 lxcfs: 4.0.11-pve1 novnc-pve: 1.3.0-2 openvswitch-switch: 2.15.0+ds1-2 proxmox-backup-client: 2.1.5-1 proxmox-backup-file-restore: 2.1.5-1 proxmox-mini-journalreader: 1.3-1 proxmox-widget-toolkit: 3.4-7 pve-cluster: 7.1-3 pve-container: 4.1-4 pve-docs: 7.1-2 pve-edk2-firmware: 3.20210831-2 pve-firewall: 4.2-5 pve-firmware: 3.3-5 pve-ha-manager: 3.3-3 pve-i18n: 2.6-2 pve-qemu-kvm: 6.2.0-1 pve-xtermjs: 4.16.0-1 qemu-server: 7.1-4 smartmontools: 7.2-pve2 spiceterm: 3.2-2 swtpm: 0.7.1~bpo11+1 vncterm: 1.7-1 zfsutils-linux: 2.1.2-pve1
root@pve:~# qm config 100 agent: 1 bios: ovmf boot: c bootdisk: scsi0 cores: 2 cpu: host,flags=+md-clear;+spec-ctrl;+ssbd;+pdpe1gb;+aes cpulimit: 2 efidisk0: Raid0:vm-100-disk-0,size=1M hotplug: disk,network,usb ide2: none,media=cdrom machine: q35 memory: 4096 name: OPNsense net0: virtio=76:003:AC:E3:04,bridge=vmbr99,queues=2,tag=222 net1: virtio=E6:AF:0A:65:25:09,bridge=vmbr0,queues=2,tag=21 net10: virtio=C6:57:71:70:0B:02,bridge=vmbr0,queues=2,tag=31 net11: virtio=5A:CB:FC:43:7A:B1,bridge=vmbr0,queues=2,tag=32 net12: virtio=EE:30:3D:AE:80:F8,bridge=vmbr0,queues=2,tag=33 net13: virtio=72:5D:10:86:681,bridge=vmbr0,queues=2,tag=41 net14: virtio=B6:53:C9:59:FE:F4,bridge=vmbr0,queues=2,tag=51 net2: virtio=FA:6C:B6:55:B2:56,bridge=vmbr0,queues=2,tag=50 net3: virtio=12:0C:1B:0A:E0:EC,bridge=vmbr2,queues=2,tag=10 net4: virtio=8A:BB:62:AD:9E:E4,bridge=vmbr2,queues=2 net5: virtio=96:AD:AF:E6B:6F,bridge=vmbr3,queues=2,tag=90 net6: virtio=C2:84:18:EA:63:84,bridge=vmbr3,queues=2,tag=15 net7: virtio=6E:8C:3D:70:09:0B,bridge=vmbr0,queues=2,tag=61 net8: virtio=0A:CC:F8:90:FF:0F,bridge=vmbr0,queues=2,tag=20 net9: virtio=42:BE:1A:13:62:59,bridge=vmbr0,queues=2,tag=30 numa: 1 ostype: other scsi0: Raid0:vm-100-disk-1,iothread=1,size=64G scsihw: virtio-scsi-pci smbios1: uuid=7c01ff41-246f-4631-8ef6-e37a7ad89082 sockets: 1 startup: order=1,down=300 tablet: 0 usb0: host=1-14 vmgenid: 5cd0205a-78f6-4e4b-bf0f-ed2eeb8d5a2e root@pve:~#
shutdown now
inside the guest or ACPI/Qemu-Guest-Agent from the PVE WebUI.