How to Use Virtual Machines on a Rented Server
- How to Use Virtual Machines on a Rented Server
This article details how to effectively utilize virtual machines (VMs) on a rented server, providing a guide for newcomers to server administration. Using VMs allows for resource optimization, application isolation, and increased flexibility compared to running everything directly on the host operating system. This guide assumes you have root access to a rented Linux server.
== Understanding Virtualization
Virtualization is the process of creating a software-based (virtual) representation of something physical. In our case, we're creating virtual representations of computer systems. Each VM operates as an independent unit, with its own operating system, applications, and resources. This is achieved through a hypervisor, which manages the allocation of physical resources to the VMs. Common hypervisors include KVM, VMware ESXi, and Xen. For this guide, we will focus on using KVM, as it's commonly available and well-integrated with Linux.
== Prerequisites
Before starting, ensure you meet the following requirements:
- A rented Linux server with root access.
- Sufficient server resources (CPU, RAM, storage) to support the desired number of VMs.
- Basic familiarity with the command line interface (CLI).
- Understanding of networking concepts such as IP addresses and routing.
== Choosing a Hypervisor: KVM
KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It leverages the Linux kernel to perform virtualization. KVM is often preferred due to its performance and tight integration with the Linux kernel.
== Installing KVM and Related Tools
The installation process varies depending on your Linux distribution. Here are examples for common distributions:
Debian/Ubuntu
Open a terminal and run the following commands:
```bash sudo apt update sudo apt install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils virt-manager sudo usermod -aG libvirt $(whoami) newgrp libvirt ```
CentOS/RHEL/Fedora
```bash sudo yum install qemu-kvm libvirt virt-install bridge-utils virt-manager sudo systemctl enable libvirtd sudo systemctl start libvirtd ```
These commands install the necessary packages for KVM, including the `libvirt` daemon (which manages VMs), the `virt-install` command-line tool, and `virt-manager` (a graphical VM management tool).
== Creating a Virtual Machine
We will use `virt-install` to create a VM. Here’s an example:
```bash sudo virt-install --name=myvm --ram=2048 --vcpus=2 --os-variant=ubuntu22.04 --disk path=/var/lib/libvirt/images/myvm.qcow2,size=20 --network bridge=virbr0 --graphics none --console pty,target_type=serial ```
Let's break down the parameters:
- `--name`: The name of the VM.
- `--ram`: The amount of RAM allocated to the VM (in MB).
- `--vcpus`: The number of virtual CPUs allocated to the VM.
- `--os-variant`: Specifies the OS type for optimization.
- `--disk`: Specifies the disk image path and size (in GB). `qcow2` is a common disk image format.
- `--network`: Configures the network connection. `virbr0` is the default NAT network.
- `--graphics`: Disables graphical output.
- `--console`: Enables console access via serial.
== Server Resource Allocation
Proper resource allocation is crucial for VM performance. Here's a table outlining typical resource requirements:
| VM Type | Recommended RAM (MB) | Recommended vCPUs | Recommended Disk Space (GB) |
|---|---|---|---|
| Web Server | 1024 - 2048 | 1 - 2 | 20 - 50 |
| Database Server | 2048 - 4096 | 2 - 4 | 50 - 100 |
| Application Server | 2048 - 8192 | 2 - 8 | 50 - 200 |
| Development/Testing | 512 - 1024 | 1 | 10 - 20 |
It's important to monitor resource usage within the VMs and adjust allocations as needed using tools like `top` or `htop` inside the VM and `virsh` on the host.
== Networking Configuration
VM networking can be configured in several ways:
- **NAT (Network Address Translation):** VMs share the host’s IP address and access the internet through it. This is the default configuration using `virbr0`.
- **Bridged Networking:** VMs get their own IP address on the same network as the host. This requires configuring a bridge interface on the host.
- **Isolated Networking:** VMs are isolated from the external network.
Here's a table showing network configuration options:
| Network Type | Advantages | Disadvantages |
|---|---|---|
| NAT | Simple to set up, good for basic internet access. | VMs are not directly accessible from the outside network. |
| Bridged | VMs are directly accessible from the network, like physical servers. | Requires more complex configuration, potential security concerns if not properly secured. |
| Isolated | High security, no external network access. | Limited functionality, VMs cannot access the internet. |
To configure bridged networking, you'll need to create a bridge interface (e.g., `br0`) and assign your server's network interface to it. Consult your distribution's documentation for specific instructions.
== Managing Virtual Machines with `virsh`
`virsh` is a command-line interface for managing VMs. Some useful commands:
- `virsh list`: Lists running VMs.
- `virsh list --all`: Lists all VMs (running and stopped).
- `virsh start <vm_name>`: Starts a VM.
- `virsh shutdown <vm_name>`: Shuts down a VM.
- `virsh destroy <vm_name>`: Forcefully stops a VM.
- `virsh console <vm_name>`: Connects to the VM's console.
== Security Considerations
- **Keep your hypervisor and related tools up to date:** Security vulnerabilities are regularly discovered and patched.
- **Secure VM access:** Use strong passwords and consider using SSH keys.
- **Firewall:** Configure a firewall on both the host and the VMs. ufw and iptables are two common options.
- **Regularly scan for vulnerabilities:** Use vulnerability scanners to identify and address potential security issues.
- **Isolate VMs:** Separate VMs based on their function and security requirements.
== Monitoring VM Performance
Monitoring VM performance is essential for identifying bottlenecks and optimizing resource allocation. Tools like `top`, `htop`, `iostat`, and `vmstat` can be used to monitor CPU, memory, disk I/O, and network usage within the VMs. On the host, `virsh stats <vm_name>` provides resource usage statistics for the VM. A summary table of useful monitoring tools is below:
| Tool | Location | Purpose |
|---|---|---|
| top | Inside VM | Real-time process monitoring |
| htop | Inside VM | Enhanced process monitoring with color and visual aids |
| iostat | Inside VM/Host | Disk I/O statistics |
| vmstat | Inside VM/Host | Virtual memory statistics |
| virsh stats | Host | VM resource usage statistics |
== Further Resources
- KVM Documentation: [1](https://www.linux-kvm.org/)
- libvirt Documentation: [2](https://libvirt.org/)
- Virtualization Overview: Virtualization
- Server Hardening: Server Hardening
- Linux Server Administration: Linux Server Administration
- Networking Fundamentals: Networking Fundamentals
Intel-Based Server Configurations
| Configuration | Specifications | Benchmark |
|---|---|---|
| Core i7-6700K/7700 Server | 64 GB DDR4, NVMe SSD 2 x 512 GB | CPU Benchmark: 8046 |
| Core i7-8700 Server | 64 GB DDR4, NVMe SSD 2x1 TB | CPU Benchmark: 13124 |
| Core i9-9900K Server | 128 GB DDR4, NVMe SSD 2 x 1 TB | CPU Benchmark: 49969 |
| Core i9-13900 Server (64GB) | 64 GB RAM, 2x2 TB NVMe SSD | |
| Core i9-13900 Server (128GB) | 128 GB RAM, 2x2 TB NVMe SSD | |
| Core i5-13500 Server (64GB) | 64 GB RAM, 2x500 GB NVMe SSD | |
| Core i5-13500 Server (128GB) | 128 GB RAM, 2x500 GB NVMe SSD | |
| Core i5-13500 Workstation | 64 GB DDR5 RAM, 2 NVMe SSD, NVIDIA RTX 4000 |
AMD-Based Server Configurations
| Configuration | Specifications | Benchmark |
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| Ryzen 5 3600 Server | 64 GB RAM, 2x480 GB NVMe | CPU Benchmark: 17849 |
| Ryzen 7 7700 Server | 64 GB DDR5 RAM, 2x1 TB NVMe | CPU Benchmark: 35224 |
| Ryzen 9 5950X Server | 128 GB RAM, 2x4 TB NVMe | CPU Benchmark: 46045 |
| Ryzen 9 7950X Server | 128 GB DDR5 ECC, 2x2 TB NVMe | CPU Benchmark: 63561 |
| EPYC 7502P Server (128GB/1TB) | 128 GB RAM, 1 TB NVMe | CPU Benchmark: 48021 |
| EPYC 7502P Server (128GB/2TB) | 128 GB RAM, 2 TB NVMe | CPU Benchmark: 48021 |
| EPYC 7502P Server (128GB/4TB) | 128 GB RAM, 2x2 TB NVMe | CPU Benchmark: 48021 |
| EPYC 7502P Server (256GB/1TB) | 256 GB RAM, 1 TB NVMe | CPU Benchmark: 48021 |
| EPYC 7502P Server (256GB/4TB) | 256 GB RAM, 2x2 TB NVMe | CPU Benchmark: 48021 |
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⚠️ *Note: All benchmark scores are approximate and may vary based on configuration. Server availability subject to stock.* ⚠️