IBM and SuSE, the Linux developer that Novell Inc. bought last week, said yesterday it received a certification for its Linux operating system that will open the door to more government business, including business with the US Department of Defense.

Armonk, New York-based International Business Machines Corp., which is planning to invest $50 million in Novell to bolster the use of Linux, said that the certification would help the SuSE version of Linux compete with other operating systems that already meet government specifications.

The SuSE version of Linux running on IBM?s computer servers based on microprocessors from Intel Corp. meets the government?s security requirements, the companies said. Linux is an open source operating system, meaning that developers are able to freely change its underlying code.

Microsoft Corp., the world?s largest software maker, already has certification from the Department of Defense. Linux has become a competitor to Microsoft in the past few years as corporations such as IBM have supported its use.