Linux is Obsolete

 In 1992, Andrew S. Tanenbaum, recognized computer scientist and author of the Minix microkernel system, wrote a Usenet article on the newsgroup comp.os.minix with the title "Linux is obsolete",[38] which marked the beginning of a famous debate about the structure of the then-recent Linux kernel. Among the most significant criticisms were that:

The kernel was monolithic and thus old-fashioned.

The lack of portability, due to the use of exclusive features of the Intel 386 processor. "Writing a new operating system that is closely tied to any particular piece of hardware, especially a weird one like the Intel line, is basically wrong."[39]

There was no strict control of the source code by any individual person.[40]

Linux employed a set of features which were useless (Tanenbaum believed that multithreaded file systems were simply a "performance hack").[41]

Tanenbaum's prediction that Linux would become outdated within a few years and replaced by GNU Hurd (which he considered to be more modern) proved incorrect. Linux has been ported to all major platforms and its open development model has led to an exemplary pace of development. In contrast, GNU Hurd has not yet reached the level of stability that would allow it to be used on a production server.[42] His dismissal of the Intel line of 386 processors as 'weird' has also proven short-sighted, as the x86 series of processors and the Intel Corporation would later become near ubiquitous in personal computers and servers.

In his unpublished book Samizdat, Kenneth Brown claims that Torvalds illegally copied code from MINIX. In May 2004, these claims were refuted by Tanenbaum, the author of MINIX:[43]

[Brown] wanted to go on about the ownership issue, but he was also trying to avoid telling me what his real purpose was, so he didn't phrase his questions very well. Finally he asked me if I thought Linus wrote Linux. I said that to the best of my knowledge, Linus wrote the whole kernel himself, but after it was released, other people began improving the kernel, which was very primitive initially, and adding new software to the system--essentially the same development model as MINIX. Then he began to focus on this, with questions like: "Didn't he steal pieces of MINIX without permission." I told him that MINIX had clearly had a huge influence on Linux in many ways, from the layout of the file system to the names in the source tree, but I didn't think Linus had used any of my code.

The book's claims, methodology and references were seriously questioned and in the end it was never released and was delisted from the distributor's site.