For any virtualization platform, there is always a client software that communicates with the host, such as vmware’s vmtools. Under KVM, it is qemu-guest-agent. Because PVE is based on KVM, the client is still qemu-guest-agent.

What is the QEMU Guest Agent?

The QEMU Guest Agent is a daemon that runs inside the guest operating system, providing various services to the host. These services facilitate communication between the host and the guest OS, enabling better management and control of the VM. The agent is particularly useful for tasks that require interaction with the guest OS without necessitating direct user intervention.

Key Features of the QEMU Guest Agent

1. Improved VM Management

The QEMU Guest Agent significantly enhances VM management capabilities. It allows the host to execute commands within the guest OS, enabling a range of administrative tasks such as file system freeze and thaw operations, user login details retrieval, and execution of scripts.

2. Efficient Backup and Restore Operations

One of the standout features of the QEMU Guest Agent is its role in improving the efficiency of backup and restore processes. By using the agent, Proxmox can ensure that the guest file system is in a consistent state before initiating a backup, thereby preventing data corruption and ensuring reliable restoration.

3. Accurate Resource Usage Reporting

The QEMU Guest Agent provides precise data on resource usage within the VM, including CPU and memory utilization, which is invaluable for administrators seeking to optimize resource allocation and ensure balanced workload distribution across the virtualized environment.

4. Enhanced Networking Capabilities

Networking configurations can be complex in virtualized environments. The QEMU Guest Agent simplifies network management by allowing the host to modify network settings within the guest OS dynamically. This feature is particularly useful in scenarios where VMs need to adapt to changing network conditions or requirements.

QEMU Agent Installation and Configuration

To leverage the benefits of the QEMU Guest Agent, it must first be installed and configured properly. Here’s a basic outline:

Install the QEMU Guest Agent Package:

For Debian-based systems:

apt install qemu-guest-agent -y

For Red Hat-based systems:

yum install qemu-guest-agent -y

For Windows:

Use the virtio driver CD to install directly. If it is win7/xp, you need to manually enter the CD, find the agent directory, and select 32-bit and 64-bit.

After the installation is complete, in the virtual machine options, check QEMU Guest Agent

How to Use QEMU Guest Agent?

For VMs with agent installed, the VM network card information will be displayed in its overview interface.

For more comprehensive usage, you need to use the qm agent command. The syntax is as follows

qm agent <vmid> <cmd>

Here vmid is the id of the VM. cmd is the command. I will list them here.

fsfreeze-freeze

fsfreeze-status

fsfreeze-thaw

# View ssd——trim

fstrim

# View disk information

get-fsinfo

# View host name

get-host-name

# View memory block information

get-memory-block-info

# View your memory

get-memory-blocks

# View system information

get-osinfo

# View time

get-time

# View time zone

get-timezone

# Users

get-users

# View the number of CPUs

get-vcpus

# View supported commands

info

# View network

network-get-interfaces

# Unknown

ping

# Shutdown

shutdown

# Hibernate, save to hard disk

suspend-disk

# Hibernate, hybrid

suspend-hybrid

# Suspend/hibernate memory

suspend-ram

All the above commands support TAB key auto-completion.

For example

# View the network card information of the VM

qm agent 101 network-get-interfaces

# View the host name

root@pve:~# qm agent 105 get-host-name

qm guest command set

qm agent is qm guest. There are four main qm guest commands:

qm guest cmd

qm guest exec

qm guest exec-status

qm guest passwd

1. qm guset cmd

This item is equivalent to qm agent

2. qm guest exec (create process)

This item is the command passed to the VM

qm guest exec <vmid> <vmcmd> --<option>

<vmid>=vmid

<vmcmd>=command in the VM. For example, ip link /docker ps, etc. The command cannot have "-", because if "-" is added, it will be set to the following <option>

<option>=A special operation, with 3 options

pass-stdin=<0/1> Whether to pass stdin to the command being executed within the VM

synchronous=<0/1> If it is 0, it returns pid. If it is 1, it returns the output result in json format

timeout=<integer>  timeout duration

Give a few examples

Check the usr directory

qm guest exec 108 ls /usr

Check whether nginx is running

qm guest exec 108 ps aux|grep nginx

Returning a bunch of means it is running, and no return if it is not running.

3. qm guest exec-status

Usage is as follows

qm guest exec-status <vmid> <pid>

This item can view the process PID status of the VM.

Note that the qm guest exec-status command is to be used in conjunction with qm guest exec. Invalid when used alone

4. qm guest passwd (reset password)

This item is very useful and the syntax is as follows:

qm guest passwd <vmid> <username> [OPTIONS]

[OPTIONS] has only one---crypted=<0/1> whether to encrypt the password. Default is 0

Example

#Change the password directly

qm guest passwd 108 root

#Applicable to changing the Windows operating system password

qm guest passwd 108 administrator

As for the following --crypted=, it is generally not added, because the password is already encrypted.

How to Protect Proxmox VM Efficiently?

Vinchin Backup & Recovery is a robust backup and disaster recovery solution supporting multiple virtualization platforms like Proxmox, VMware, Hyper-V, XenServer, Red Hat Virtualization, XCP-ng, and Oracle OLVM. It features automatic, agentless, LAN/LAN-Free backups, offsite copies, effective data reduction, and cloud archiving, adhering to the 3-2-1 golden backup rule to ensure data security and integrity. For recovery, it offers instant VM recovery to minimize RTO to 15 seconds and file-level granular restores. Enhanced with data encryption and anti-ransomware protection, it secures Proxmox VE VM backups. Additionally, it facilitates VM migration across over ten virtual platforms, simplifying data transfers between Proxmox and other systems. The user-friendly web console streamlines backup management and VM job creation without manual intervention.

It only takes 4 steps for you to backup Proxmox VE VMs:

1. Select the backup object.

2. Select backup destination.

3. Select backup strategies.

4. Review and submit the job.

Vinchin Backup & Recovery, trusted by thousands of companies worldwide, offers a 60-day full-featured trial. Share your specific Proxmox VE environment needs, and we'll provide a custom solution that integrates seamlessly with your IT infrastructure.

Proxmox QEMU Agent FAQs

1. Q: How to check if QEMU guest agent is installed?

A: To check if the QEMU guest agent is installed, log into the VM and run the command “systemctl status qemu-guest-agent”. If it is installed, you will see the service status; otherwise, you'll get an error indicating the service is not found.

2. Q: What is the difference between Proxmox VE and QEMU?

A: Proxmox VE is a complete open-source server virtualization management solution that integrates KVM hypervisor and LXC containers, offering a web-based interface for managing virtual machines, containers, storage, and networks. QEMU, on the other hand, is a generic and open-source machine emulator and virtualizer that can run operating systems and programs for one machine on a different machine, often used in conjunction with KVM to provide virtualization in Proxmox VE.

Conclusion

The Proxmox QEMU Guest Agent is an essential tool for administrators looking to maximize the efficiency and functionality of their virtualized environments. By facilitating improved VM management, efficient backup processes, accurate resource reporting, and enhanced networking capabilities, the QEMU Guest Agent plays a pivotal role in modern virtualization solutions.