POSIX.1 (FIPS 151-2) Certification

A Historic Development for Linux

By Ian Nandrha, Lasermoon Ltd.

Linux-FT is the first Linux distribution to be Certified against a recognised, industry standard - POSIX.1 (FIPS 151-2)

Before we discuss the full details, a little background to Linux and POSIX. Full details of this certification and release can be obtained by replying to info@lasermoon.co.uk or from http://www.lasermoon.co.uk Distribution details and mirror sites appear at the end of this announcement.


Linux is often described as "POSIX-ish", "Mostly POSIX" and other equally imprecise terms. Magazine articles sometimes describe Linux as POSIX Compliant. Whilst Linux has certainly been developed towards POSIX standards, it has only now been Certified to an POSIX standard. POSIX "Compliance", "POSIX'ish" and other terms only provide an indication that POSIX standards may have been referred to during development.

Unlike the term UNIX, which can only be used to describe products that pass the X/Open validation suites, the term POSIX can be used with freedom as there is no governing body to regulate its use - or misuse.

The message (POSIX) displayed when some Linux boots is meaningless as it does not define which POSIX standard it refers to or if it has been certified. At best, the Linux displaying the (POSIX) message has been developed towards POSIX standards and is at worst deliberately misleading. To the best of our knowledge, this is the first time that Linux has actually been tested and passed against the real POSIX test suites. Linux-FT has been certified against POSIX.1

What's Conformance Testing?

Essentially the product is tested against validation software produced and released by a standards body and validated by an Independent Certification Laboratory.

Current Linux distributions are "tested" on the Internet (we actually heard a comment along the lines of ".. we don't need Conformal Testing, we have the best testing in the world on the Internet." Without opening the debate about Internet testing, Conformal Testing and Certification...

POSIX.1 FIPS 151-2 Certification

This is a milestone in Linux development. For the first time a Linux has been certified against an International standard, POSIX.1 (FIPS 151-2) The reasons for certification are simple :

Why Certify?

The decision to actually Certify Linux was made to remove the criticism that Linux is not a real, stable and serious operating system. It has widely accepted that Linux requires major Applications to be ported to it. Currently ISV's (Independent Software Vendors) have little real proof that Linux will actually support their applications if they choose to invest time and money into a port. There is also a continual fear in the ISV community that Linux will have changed during the porting process (which can take 3 months) compromising their investment. For Linux to have a wide base of stable applications, the ISV community have to have proof that Linux is a credible platform to port onto.

POSIX.1 certification provides this proof in the following ways :

POSIX.1 Certification also makes it easier for large organisations to use Linux as the "It's not tested" argument is now clearly not true.

A Stable Platform

An Application is only as good as the platform supporting it and ISV's require a stable operating system with consistent and known specification. Providing a specification for Linux has historically been a problem which has discouraged both ISV's from porting and organisations from using Linux. POSIX.1 certification gives the level of standardisation and consistency required to overcome such objections and makes Linux a more attractive alternative.

The Feel Good Factor

Standards accreditation does not imply high quality or reliability, although a certified system will always be better tested than a non-certified system. It can be argued (and often is) that an unreliable, inefficient system can pass certification. True, it is not a measure of quality, but it is an independent assessment of functionality. Put more simply: you have an independent body saying that it works. It also means that products will be easier to port, more consistent and stable It means that a future release, Certified to the same standard, will perform and behave in the same way as its predecessor.

It also shows that Linux is maturing, distancing it from situations where it is being misrepresented - there is at least one advertisement describing Linux as being "100% UNIX", a statement which is both illegal and dangerously misleading.

Consistent, Stable and Standard

Companies porting to Linux can now do so knowing that future releases will behave in a consistent manner. This standardised functionality makes support easier as there is a standard against which "bugs" can be compared.

Which Linux's are Certified?

At present only Linux-FT and discussions are proceeding with Linus Torvalds about ensuring that the considerable investment in the certification process is fed back into future Linux kernels. We will be working with Linus to ensure that new kernels have passed the tests required for certification.

There is more to POSIX.1 certification than just the kernel. The complier has been enhanced, Libraries upgraded in addition to countless other major and minor code changes.

If you are in any doubt if a Linux distribution is certified, ask to see the POSIX Conformance document and Certificate.

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