TUX web server
Encyclopedia
The TUX web server is an in-kernel web server
for Linux
licensed under the GNU General Public License
(GPL). It was maintained by Ingo Molnár
.
It is currently limited to serving static web pages and coordinating between kernelspace modules, userspace modules, and regular userspace web server daemons
that provide dynamic content. Regular userspace web servers do not need to be altered in any way for TUX to coordinate with them. However, userspace code has to use a new interface based on the
The main differences between TUX and other webservers include:
While only being able to serve static web pages could be seen as a significant disadvantage, TUX has one significant advantage: it is able to serve pages faster than traditional web servers. This is largely due to its place directly within the kernel, where it can improve performance by taking advantage of facilities not available to traditional web servers, which run outside of the kernel. However, this also means that TUX does not generate dynamic content. Because it is running within the kernel, such dynamic content cannot take advantage of functions that the kernel provides to userspace programs, and would create tremendous security issues.
TUX is capable of launching CGI
programs to provide dynamic content. However, CGI suffers from significant performance limitations, so a CGI-heavy site would gain no performance advantage from using TUX. TUX can also redirect any request it cannot process to a traditional userspace web server daemon, for example Apache
or lighttpd
. This allows TUX to handle both dynamic content and errors in a safer, faster, and RFC
-correct manner.
TUX has never been an integrated part of the official Linux kernel, although it has been shipped in some distributions, notably Red Hat
, SuSE and Fedora Core. It served as a test bed (and motivator) for many features which were integrated separately. One major component was the Native POSIX Thread Library
, which, with the right tuning parameters, allows userspace web servers to serve web pages at a speed very close to that of a kernelspace web server like TUX but without its limitations. Core kernel developers also argued that having an HTTP daemon within the kernel is dangerous. For example, a common bug such as a buffer overflow
within TUX could give an attacker superuser
control over the machine. Therefore, it is much safer to keep the HTTP daemon entirely within userspace, where a bug does not necessarily give an attacker total control. However, some Linux distributions, such as Fedora
, have added TUX back into kernels.
In-kernel web server
An in-kernel web server is an unlimited HTTP server that runs in kernel space or equivalent. Also called "accelerator".- Benefits :* Performance. The path taken by data from disk to network. Proper asynchronous zero-copy interfaces would make this available from user-space.* Scalability with...
for Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
licensed under the GNU General Public License
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
(GPL). It was maintained by Ingo Molnár
Ingo Molnar
Ingo Molnár, currently employed by Red Hat, is a Hungarian Linux hacker. He is best known for his contributions to the operating system in terms of security and performance...
.
It is currently limited to serving static web pages and coordinating between kernelspace modules, userspace modules, and regular userspace web server daemons
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
that provide dynamic content. Regular userspace web servers do not need to be altered in any way for TUX to coordinate with them. However, userspace code has to use a new interface based on the
tux(2) system call.The main differences between TUX and other webservers include:
- TUX runs partly within a customized version of the Linux kernelLinux kernelThe Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
and partly as a userspace daemon. - With a capable network cardNetwork cardA network interface controller is a computer hardware component that connects a computer to a computer network....
, TUX enables scatter-gatherVectored I/OIn computing, vectored I/O, also known as scatter/gather I/O, is a method of input and output by which a single procedure-call sequentially writes data from multiple buffers to a single data stream or reads data from a data stream to multiple buffers. The buffers are given in a vector of buffers...
DMADirect memory accessDirect memory access is a feature of modern computers that allows certain hardware subsystems within the computer to access system memory independently of the central processing unit ....
from the page cache directly to the network. - TUX is only able to serve static web pages.
While only being able to serve static web pages could be seen as a significant disadvantage, TUX has one significant advantage: it is able to serve pages faster than traditional web servers. This is largely due to its place directly within the kernel, where it can improve performance by taking advantage of facilities not available to traditional web servers, which run outside of the kernel. However, this also means that TUX does not generate dynamic content. Because it is running within the kernel, such dynamic content cannot take advantage of functions that the kernel provides to userspace programs, and would create tremendous security issues.
TUX is capable of launching CGI
Common Gateway Interface
The Common Gateway Interface is a standard method for web servers software to delegate the generation of web pages to executable files...
programs to provide dynamic content. However, CGI suffers from significant performance limitations, so a CGI-heavy site would gain no performance advantage from using TUX. TUX can also redirect any request it cannot process to a traditional userspace web server daemon, for example Apache
Apache HTTP Server
The Apache HTTP Server, commonly referred to as Apache , is web server software notable for playing a key role in the initial growth of the World Wide Web. In 2009 it became the first web server software to surpass the 100 million website milestone...
or lighttpd
Lighttpd
lighttpd is an open-source web server more optimized for speed-critical environments than common products while remaining standards-compliant, secure and flexible...
. This allows TUX to handle both dynamic content and errors in a safer, faster, and RFC
Request for Comments
In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...
-correct manner.
TUX has never been an integrated part of the official Linux kernel, although it has been shipped in some distributions, notably Red Hat
Red Hat
Red Hat, Inc. is an S&P 500 company in the free and open source software sector, and a major Linux distribution vendor. Founded in 1993, Red Hat has its corporate headquarters in Raleigh, North Carolina with satellite offices worldwide....
, SuSE and Fedora Core. It served as a test bed (and motivator) for many features which were integrated separately. One major component was the Native POSIX Thread Library
Native POSIX Thread Library
The Native POSIX Thread Library is a software feature that enables the Linux kernel to run programs written to use POSIX Threads efficiently.-History:...
, which, with the right tuning parameters, allows userspace web servers to serve web pages at a speed very close to that of a kernelspace web server like TUX but without its limitations. Core kernel developers also argued that having an HTTP daemon within the kernel is dangerous. For example, a common bug such as a buffer overflow
Buffer overflow
In computer security and programming, a buffer overflow, or buffer overrun, is an anomaly where a program, while writing data to a buffer, overruns the buffer's boundary and overwrites adjacent memory. This is a special case of violation of memory safety....
within TUX could give an attacker superuser
Superuser
On many computer operating systems, the superuser is a special user account used for system administration. Depending on the operating system, the actual name of this account might be: root, administrator or supervisor....
control over the machine. Therefore, it is much safer to keep the HTTP daemon entirely within userspace, where a bug does not necessarily give an attacker total control. However, some Linux distributions, such as Fedora
Fedora (operating system)
Fedora is a RPM-based, general purpose collection of software, including an operating system based on the Linux kernel, developed by the community-supported Fedora Project and sponsored by Red Hat...
, have added TUX back into kernels.
See also
- Comparison of web server softwareComparison of web server software-Overview:-Features:- Operating system support :...
- web serverWeb serverWeb server can refer to either the hardware or the software that helps to deliver content that can be accessed through the Internet....
- HttpdHttpdhttpd stands for Hypertext Transfer Protocol Daemon .The implied meaning can be:* Apache HTTP Server* Canopy HTTPd HTTP server* CERN HTTPd HTTP server* Lighttpd HTTP server* NCSA HTTPd HTTP server...