{"id":37530,"date":"2019-10-31T22:18:10","date_gmt":"2019-10-31T19:18:10","guid":{"rendered":"https:\/\/prohoster.info\/blog\/ip-kvm-cherez-qemu\/"},"modified":"2019-10-31T22:18:10","modified_gmt":"2019-10-31T19:18:10","slug":"ip-kvm-cherez-qemu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/administrirovanie\/ip-kvm-cherez-qemu","title":{"rendered":"IP-KVM via QEMU","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"IP-KVM
\n
\nTroubleshooting operating system boot issues on servers without KVM is a challenging task. We create KVM-over-IP through a recovery image and a virtual machine.<\/p>\n

In case of problems with the operating system on the remote server<\/a><\/noindex>, the administrator loads a recovery image and carries out the necessary work. This method works well when the cause of the failure is known and the recovery image and the operating system installed on the server belong to the same family. If the cause of the failure is not yet known, it is necessary to observe the boot process of the operating system.
\n<\/a><\/noindex><\/p>\n

Remote KVM<\/h2>\n

\nAccess to the server console can be achieved using built-in tools such as IPMI or Intel\u00ae vPro\u2122, or with external devices called IP-KVM. There are situations where none of the listed technologies are available. However, this is not the end. If the server can be remotely rebooted into a recovery image based on a Linux family operating system, KVM-over-IP can be quickly organized.<\/p>\n

The recovery image is a fully functional operating system that resides in RAM. Therefore, we can run any software, including virtual machines (VMs). This means that a VM can be launched, inside which the server's operating system will operate. Access to the VM console can be arranged, for example, via VNC.<\/p>\n

To start the server's operating system inside a VM, you need to specify the server disks as the VM disks. In Linux family operating systems, physical disks are represented as block devices of the type \/dev\/sdX<\/b>, which can be operated on like regular files.<\/p>\n

Some hypervisors, such as QEMU and VirtualBox, allow storing VM data in a \u2018raw\u2019 format, which means only the storage data without hypervisor metadata. Thus, the VM can be launched using the physical disks of the server.<\/p>\n

This method requires resources to run the recovery image and the VM within it. However, with four or more gigabytes of RAM, this will not be a problem.<\/p>\n

Preparing the Environment<\/h2>\n

\nA lightweight and simple program can be used as a virtual machine QEMU<\/a><\/noindex>, which is often not part of the recovery image, so it needs to be installed separately. The recovery image we offer to clients is based on Arch Linux<\/a><\/noindex>, which uses the package manager pacman<\/b>.<\/p>\n

First, make sure that the recovery image uses the latest software versions. You can check and update all OS components with the following command:<\/p>\n

pacman -Suy<\/code><\/p>\n

After the update, you need to install QEMU. The command for installation via pacman will look like this:<\/p>\n

pacman -S qemu<\/code><\/p>\n

Let's check that qemu has been installed correctly:<\/p>\n

root@sel-rescue ~ # qemu-system-x86_64 --version
\nQEMU emulator version 4.0.0
\nCopyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers<\/code><\/p>\n

If everything is fine, the recovery image is ready to use.<\/p>\n

Starting the virtual machine<\/h2>\n

\nFirst, determine the amount of resources allocated to the VM, and find the paths to the physical disks. In our case, we will allocate two cores and two gigabytes of RAM to the virtual machine, and the disks are located at \/dev\/sda<\/b> and \/dev\/sdb<\/b>. Let's start the VM:<\/p>\n

qemu-system-x86_64
\n -m 2048M
\n -net nic -net user
\n -enable-kvm
\n -cpu host,nx
\n -M pc
\n -smp 2
\n -vga std
\n -drive file=\/dev\/sda,format=raw,index=0,media=disk
\n -drive file=\/dev\/sdb,format=raw,index=1,media=disk
\n -vnc :0,password
\n -monitor stdio<\/code><\/p>\n

A bit more about what each parameter means:<\/p>\n