115 lines
3.3 KiB
Markdown
115 lines
3.3 KiB
Markdown
[[!meta title="Linux Virtual Machine Overview"]]
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This document is ***WORK IN PROGRESS***
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## Introduction
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This article tries to summarise Linux Virtual Machine
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methods and is in its early stage. It does not focus
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on different types of hypervisors, but more on the
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issues and features you get with each hypervisor.
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### Host Kernel
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Some supervisors need their own (modified Linux) kernel
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to operate, whereas others work with any Linux kernel.
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Though some of them again need some configurations
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to be turned on in the stock kernel.
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### VM Installation
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Depending on the hypervisor, there are different requirements
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and methods for the installation:
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* Installation can be done within the VM for completly isolated machines
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* Installation must be done outside / on the host for systems without own kernel
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Some hypervisors can boot from the network, whereas others just
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create a very lightweight isolation and boot an installed system
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only.
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### Guest OS changes
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Some hypervisors require changes to the virtual machines, to be able
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to run successfully. Others allow a original OS version to be
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installed.
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### Network configuration
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Whether the VM is attached to a bridge, a tun/tap device, treated
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as a normal process, there may be a lot of different configurations.
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Furthermore, firewall (masquerade/nat) configurations may be necessary.
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Additionally, some of the hypervisors support dynamic allocation
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of mac or even ip addresses.
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### Templates
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Some hypervisors support reusage of installations.
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### Management
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Most hypervisors contain some minor collection of utilities
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to manage virtual machines. Some libraries / frameworks
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try to integrate those utilities, to abstract the different
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implementations.
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Typical issues are:
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* Autostart machines on startup / autostop on shutdown
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* Creation of new VMs / including template handling
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* Manual start/stop of VMs
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* Listing of running / existing VMs
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### Automated usage
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Especially interesting for a sysadmin is, how easy a system can
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be automated, which steps need to be taken to get a new image
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or copy of an existing one. This aspect is one focus of this
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document.
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## Hypervisors
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[[!table data="""
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Name | Host Kernel | Guest OS changes | Installation
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[QEMU](http://wiki.qemu.org/) | Original | no | inside
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[KVM](http://www.linux-kvm.org/) | Original w/KVM | no | inside
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[Lguest](http://lguest.ozlabs.org/) | Original w/Lguest | ? | ?
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[Linux Containers](http://lxc.sourceforge.net/) | Original w/Containers | yes | outside
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[Linux VServer](http://linux-vserver.org) | Own | ? | ?
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[User Mode Linux](http://user-mode-linux.sourceforge.net/) | Original | ? | outside
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[OpenVZ](http://wiki.openvz.org/Main_Page) | Own | ? | ?
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[Virtualbox](http://www.virtualbox.org/) | Original+Modules | no | inside
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[VMWare](http://www.vmware.com/) | Original+Modules / Own | no | inside
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[Xen](http://www.xen.org/) | Own | ? | ?
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"""]]
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### lxc
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Some hints on lxc:
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* Helper scripts existent (lxc-debian, lxc-fedora, ...)
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* adjust init. change dev. do not run udev (why?)
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* Root open in the filesystem
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* No network specified = all from host accessible!
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## Management Libraries / Frameworks
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[[!table data="""
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Name | Hints
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Ganetti |
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Libvirt |
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"""]]
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## Poor man's management
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This sections describes typical vm management tasks, done with
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easy commands.
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### Creating a new (sparse) image file
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dd if=/dev/zero of=<filename> bs=1 count=0 seek=<gigabytes>G
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[[!tag net unix]]
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