nixCraft » kernel

Visual Representations Of Linux File Systems

nixCraft — Tue, 16 Jun 2009 19:49:38 +0000

This is an interesting visualization techniques for software analysis. From the article:

Despite being a very important part of any operating system, file systems tend to get little attention. Linux has three editions for Linux Device Drivers, another three for Understanding the Linux Kernel and two for Linux Kernel Development. The first is a detail analysis of one particular Linux Kernel tree and the second is a shorter one done over a large number of file systems from Linux Kernel 2.6.0 to 2.6.29. After that there is a small section that shows some aspects of the BSD family. After conclusions there is an appendix consisting of three things: the first one explains how the file systems for Linux were compiled, the second one shows timelines for the releases of Linux Kernel, FreeBSD, NetBSD and OpenBSD; the last is a detailed map of the external symbols of the kernel modules analyzed in the second section.

A Visual Expedition Inside the Linux File Systems

Linux x86_64: Detecting Hardware Errors

nixCraft — Tue, 02 Jun 2009 21:54:58 +0000

The Blue Screen of Death (BSoD) is used for the error screen displayed by Microsoft Windows, after encountering a critical system. Linux / UNIX like operating system may get a kernel panic. It is just like BSoD. The BSoD and a kernel panic generated using a Machine Check Exception (MCE). MCE is nothing but feature of AMD / Intel 64 bit systems which is used to detect an unrecoverable hardware problem.

Program such mcelog decodes machine check events (hardware errors) on x86-64 machines running a 64-bit Linux kernel. It should be run regularly as a cron job on any x86-64 Linux system. This is useful for predicting server hardware failure before actual server crash.

XEN Virtualization Set The MTU For xenbr0 Interface

nixCraft — Wed, 31 Dec 2008 18:40:08 +0000

I've already written about setting the MTU (Maximum Transmission Unit) under Linux including Jumbo frames (FreeBSD specific MTU information is here).

With this quick tip you can increase MTU size to get a better networking performance.

Download of the day: Linux Kernel 2.6.28

nixCraft — Sat, 27 Dec 2008 14:36:54 +0000

Linux kernel version 2.6.28 has been released and available for download. The new version includes following stable and new features:

a] ext4 file system - The ext4 filesystem can support volumes with sizes up to 1 exbibyte and files with sizes up to 16 TiB. ext4 removes ext3 64-bit storage limits and adds other performance improvements.

b] Graphics Execution Manager (GEM) - It is a a modern memory manager specialized for use in device drivers for graphics chipsets. It manages graphics memory, controls the execution context and manages the Non-Uniform Memory Access (NUMA) environment on modern graphics chipsets. The "xf86-video-intel" device driver will feature GEM integration.

c] Other features - Stable USB drivers, KVM, bug fixes and other stuff.

=> Download Linux kernel 2.6.28 here. You may also find our kernel compile tutorial useful.

Are the Solid-State Drive Supported on Linux?

nixCraft — Wed, 17 Dec 2008 14:39:52 +0000

A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data. A SSD emulates a hard disk drive interface, thus easily replacing it in most applications. An SSD using SRAM or DRAM (instead of flash memory) is often called a RAM-drive.

Security Update: Debian Linux Kernel Local / Remote Vulnerabilities

nixCraft — Thu, 04 Dec 2008 18:54:14 +0000

Debian project today released a pair of security updates to plug at least ten security holes in its core called Linux kernel. Several vulnerabilities have been discovered in the Linux kernel that may lead to a denial of service or privilege escalation. This update has been rated as having important security impact.

Linux: Boot a 2TB+ partition or Larger Array Using Grub

nixCraft — Thu, 04 Dec 2008 07:13:58 +0000

I've already written about creating a partition size larger than 2TB under Linux using GNU parted command with GPT. In this tutorial, I will provide instructions for booting to a flat 2TB or larger RAID array under Linux using the GRUB boot loader.

Sun Netra ATCA CP3220 CP3250 10-Gigabit Ethernet Drivers

nixCraft — Wed, 03 Dec 2008 14:30:20 +0000

The Sun Netra brand has been used for a variety of server computers from Sun Microsystems. These servers used for various purposes such as telecommunications applications.

Linux: Should You Use Twice the Amount of Ram as Swap Space?

nixCraft — Wed, 19 Nov 2008 08:50:49 +0000

Linux and other Unix-like operating systems use the term "swap" to describe both the act of moving memory pages between RAM and disk, and the region of a disk the pages are stored on. 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?

How To Reduce Linux Computer Power Consumption

nixCraft — Sun, 16 Nov 2008 16:26:37 +0000

The Advanced Configuration and Power Interface (ACPI) specification is an open standard operating system-centic device configuration and power management. You can easily reduce your PC's power consumption through smart activity monitors.
With the tools and code presented, you can reduce your power consumption through a series of rules regarding application usage. After tuning your kernel, hdparm, ACPI, and CPU settings, add these application monitors to more effectively enter your low-power states.

mount forcedirectio: Disable Linux CIFS / NFS Client Caching

nixCraft — Sun, 16 Nov 2008 09:03:15 +0000

If your network is heavily loaded you may see some problem with Common Internet File System (CIFS) and NFS under Linux. By default Linux CIFS mount command will try to cache files open by the client. You can use mount option forcedirectio when mounting the CIFS filesystem to disable caching on the CIFS client. This is tested with NETAPP and other storage devices and Novell, CentOS, UNIX and Red Hat Linux systems. This is the only way to avoid data mis-compare and problems.

Parallel NFS: Read / Write Hundreds of Gigabytes Per Second

nixCraft — Thu, 13 Nov 2008 12:17:31 +0000

NFS is pretty old file sharing technology for UNIX based system and storage systems. However, it suffers from performance issues. NFSv4.1 address data access issues by adding a new feature called parallel NFS (pNFS) - a method of introducing Data Access Parallelism. The end result is ultra fast file sharing for clusters and high availability configurations.

The Network File System (NFS) is a stalwart component of most modern local area networks (LANs). But NFS is inadequate for the demanding input- and output-intensive applications commonly found in high-performance computing -- or, at least it was. The newest revision of the NFS standard includes Parallel NFS (pNFS), a parallelized implementation of file sharing that multiplies transfer rates by orders of magnitude.

Red Hat Enterprise Linux 5 IMPORTANT Security Update [ 4-Nov-2008 ]

nixCraft — Tue, 04 Nov 2008 21:35:30 +0000

Red Hat today released kernel updates to fix at least 15 security flaws in its core called Linux kernel. RHEL users can grab the latest updates from RHN website or by simply running yum update command. This update has been rated as having important security impact.

Linux Supports More Devices Than Any Other OS

nixCraft — Mon, 03 Nov 2008 13:59:10 +0000

Interesting read and claim has been independently verified by somebody from Microsoft.

Greg Kroah-Hartman is a longtime developer of the Linux kernel, known for his work maintaining USB drivers as well as for packaging the SUSE kernel at Novell. O'Reilly Media recently interviewed Greg about his claim that the Linux kernel now supports more devices than any other operating system ever has, as well as why binary-only drivers are illegal, and how the kernel development process works.

Read full interview: How Linux Supports More Devices Than Any Other OS, Ever

Would The Internet Exist Without Linux? Yes, Very Likely.

nixCraft — Thu, 30 Oct 2008 05:31:05 +0000

This is the dumbest article ever. Would the internet as we know it exist without Linux? Absolutely not. Where Linux shines the most is in its server applications - no question, says Rich Menga.

Is The Linux Community Afraid of Opensolaris?

nixCraft — Mon, 20 Oct 2008 13:17:52 +0000

It's about time someone wrote this article. I know the headline is a little bit provoking. But when you think about some comments from Linux proponents you could think so.

Linus Torvalds Blog

nixCraft — Tue, 07 Oct 2008 15:41:30 +0000

Linus is best known for Linux kernel and still active Kernel maintainer started blogging. So if you're interested more about Linus and his life read Linus Torvalds's blog here.

Linux Support For Intel Core i7 (Nehalem) Processors

nixCraft — Fri, 03 Oct 2008 20:20:11 +0000

Linux support the Intel Core i7 (codenamed Nehalem) processors under latest kernel and CentOS 4.7 and 5.2

Troubleshooting Lighttpd Chrooted RedHat PHP Version 5.1.6-20.el5_2.1

nixCraft — Wed, 01 Oct 2008 08:14:35 +0000

It appears that latest php version 5.1.6-20.el5_2.1 under RHEL / CentOS Linux v5.2 has made some major changes. As a result choort jail setup using previous instructions no longer works. PHP is crashing with segmentation fault errors. So I had to trace php errors using strace command.

Sun Solaris on its Deathbed – Claims Jim Zemlin

nixCraft — Thu, 25 Sep 2008 08:23:48 +0000

Jim Zemlin is executive director of the Linux Foundation claims Solaris UNIX is irrelevant and Linux is future. Is Sun Solaris on its deathbed? Linux backers claim Solaris is irrelevant; Sun of course disagrees.