Linux Virtual Server

Quality 0.50 · 2 views · Updated 2 months ago

Load-balancing software

title: "Linux Virtual Server" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["high-availability-cluster-computing", "free-network-related-software", "internet-software-for-linux", "linux-only-free-software", "parallel-computing"] description: "Load-balancing software" topic_path: "technology/computing" source: "https://en.wikipedia.org/wiki/Linux_Virtual_Server" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Load-balancing software ::

::data[format=table title="Infobox software"]

Field	Value
name	Linux Virtual Server
logo	Lvslogo.png
logo caption	LVS official logo
logo_size	200px
logo_alt	LVS official logo
screenshot
author	Wensong Zhang
developer	et al.
released
latest release date
latest preview date
programming language	C
operating system	Linux
genre	load balancing
license	GNU General Public License
website
::

Linux Virtual Server (LVS) is load balancing software for Linux kernel–based operating systems.

LVS is a free and open-source project started by Wensong Zhang in May 1998, subject to the requirements of the GNU General Public License (GPL), version 2. The mission of the project is to build a high-performance and highly available server for Linux using clustering technology, which provides good scalability, reliability and serviceability.

Overview

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/4d/Wikipedia_webrequest_2022.png" caption="LVS as used by [[Wikimedia Foundation]] in 2022."] ::

The major work of the LVS project is now to develop advanced IP load balancing software (IPVS), application-level load balancing software (KTCPVS), and cluster management components.

IPVS: an advanced IP load balancing software implemented inside the Linux kernel. The IP Virtual Server code is merged into versions 2.4.x and newer of the Linux kernel mainline.{{cite web | url = http://www.linuxvirtualserver.org/software/ipvs.html | title = IPVS Software - Advanced Layer-4 Switching | date = 2011-02-08 | accessdate = 2014-01-12 | publisher = linuxvirtualserver.org
KTCPVS: implements application-level load balancing inside the Linux kernel, still under development.

LVS can be used for building highly scalable and highly available network services, such as web, email, media and VoIP services, and integrating scalable network services into large-scale reliable e-commerce or e-government applications. LVS-based solutions already have been deployed in many real applications throughout the world, including Wikipedia.

The LVS components depend upon the Linux Netfilter framework, and its source code is available in the net/netfilter/ipvs subdirectory within the Linux kernel source. LVS is able to handle UDP, TCP layer-4 protocols as well as FTP passive connection by inspecting layer-7 packets. It provides a hierarchy of counters in the /proc directory.

The userland utility program used to configure LVS is called ipvsadm, which requires superuser privileges to run.

Schedulers

LVS implements several balancing schedulers, listed below with the relevant source files:{{cite web | url = http://www.linuxvirtualserver.org/docs/scheduling.html | title = Job Scheduling Algorithms in Linux Virtual Server | date = 2011-02-08 | accessdate = 2013-11-24 | publisher = linuxvirtualserver.org

Round-robin (ip_vs_rr.c)
Weighted round-robin (ip_vs_wrr.c)
Least-connection (ip_vs_lc.c)
Weighted least-connection (ip_vs_wlc.c)
Locality-based least-connection (ip_vs_lblc.c)
Locality-based least-connection with replication (ip_vs_lblcr.c)
Destination hashing (ip_vs_dh.c)
Source hashing (ip_vs_sh.c)
Shortest expected delay (ip_vs_sed.c)
Never queue (ip_vs_nq.c)
Maglev hashing (ip_vs_mh.c)

Glossary

Commonly used terms include the following:{{cite web | url = http://bobcares.com/blog/linux-virtual-server-load-balance-your-networked-services/ | title = Linux Virtual Server: Load Balance Your Networked Services | year = 2008 | accessdate = 2013-11-24 | publisher = bobcares.com

LVS director: load balancer that receives all incoming client requests for services and directs them to a specific "real server" to handle the request
Real servers: nodes that make up an LVS cluster which are used to provide services on the behalf of the cluster
Client computers: computers requesting services from the virtual server
VIP (Virtual IP address): the IP address used by the director to provide services to client computers
RIP (Real IP address): the IP address used to connect to the cluster nodes
DIP (Directors IP address): the IP address used by the director to connect to network of real IP addresses
CIP (Client IP address): the IP address assigned to a client computer, that it uses as the source IP address for requests being sent to the cluster

Examples

Setting up a virtual HTTP server with two real servers:

::code[lang=bash] ipvsadm -A -t 192.168.0.1:80 -s rr ipvsadm -a -t 192.168.0.1:80 -r 172.16.0.1:80 -m ipvsadm -a -t 192.168.0.1:80 -r 172.16.0.2:80 -m ::

The first command assigns TCP port 80 on IP address 192.168.0.1 to the virtual server. The chosen scheduling algorithm for load balancing is round-robin (-s rr). The second and third commands are adding IP addresses of real servers to the LVS setup. The forwarded network packets shall be masked (-m).

Querying the status of the above configured LVS setup:

::code[lang=text]

ipvsadm -L -n

IP Virtual Server version 1.0.8 (size=65536) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.0.1:80 rr -> 172.16.0.2:80 Masq 1 3 1 -> 172.16.0.1:80 Masq 1 4 0 ::

References

Wensong Zhang. (2011-02-08). "KTCPVS Software - Application-Level Load Balancing". Linuxvirtualserver.org.
"Understanding Virtual Server".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::