Unix Archive

Stayin’ Alive with GNU Screen

If you've spent hours on a task, such as debugging an application, it can be maddening to lose your work in an instant. This article shows you how to keep your shell and your work alive, even across multiple sessions and dropped connections using GNU Screen. Screen is a remarkable tool that you will quickly find invaluable in any work you perform on the command line. In fact, use it once, and you will wonder how you ever lived without it.

Protothreads for UNIX

Protothreads are a type of extremely lightweight threads - each protothread requires only two bytes of memory - that are usually used for embedded firmware programming, where memory is at a premium. Protothreads combine the low overhead with event-driven programming with the algorithmic clarity of threaded programming.

Debunking the “2x Ram as Swap Space” Rule

Linux and other Unix-like operating systems use the term "swap" to describe both the act of moving memory pages between RAM and disk. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I’ve 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space really required? How big should your Linux / UNIX swap space be?

More Details on HP’s Virtualization Efforts

OSNews recently ran a story on UNIX virtualization functionality which was a bit shallow on technical details. HP's Christophe de Dinechin (who had already begun working on virtualization at HP when we interviewed him several years ago, but couldn't talk about it then) contacted us to tell us he'd gone into more technical detail on his blog here and here saying, "They are a bit long, and probably boring to a general audience, but since your readers are generally more interested in OS technology than the average population, I thought I'd bring these to your attention."

MIT Releases Source of MULTICS

"This is extraordinary news for all nerds, computer scientists and the Open Source community: the source code of the MULTICS operating system (Multiplexed Information and Computing Service), the father of UNIX and all modern OSes, has finally been opened . Multics was an extremely influential early time-sharing operating system started in 1964 and introduced a large number of new concepts, including dynamic linking and a hierarchical file system. It was extremely powerful, and UNIX can in fact be considered to be a 'simplified' successor to MULTICS (the name 'Unix' is itself a hack on 'Multics'). The last running Multics installation was shut down on October 31, 2000."

Fiwix 0.3.1 Released

GNU/Fiwix is a 32-bit x86 operating system kernel based on the Unix architecture and fully focused on being Linux compatible. It is designed exclusively for educational purposes, so the kernel code is kept as simple as possible for the benefit of students. In the latest version, the virtual memory manager code has been improved to support SVGAlib-based applications and to add the ability to mmap() physical addresses. The way to map physical addresses in the /dev/mem driver has been improved. The mmap() and readpage() methods have been added to the VFS structure. Among other improvements in the VFS layer, the code to build with gcc 4.x has been fixed.