nixCraft » Hardware

HowTo: Create sar Graphs With kSar [ Identifying Linux Bottlenecks ]

nixCraft — Tue, 15 Dec 2009 06:33:21 +0000

The sar command collect, report, or save UNIX / Linux system activity information. It will save selected counters in the operating system to the /var/log/sa/sadd file. From the collected data, you get lots of information about your server:

CPU utilization
Memory paging and its utilization
Network I/O, and transfer statistics
Process creation activity
All block devices activity
Interrupts/sec etc.

sar output can be used for identifying server bottlenecks. However, analyzing information provided by sar can be difficult, so use kSar, which can take sar output and plot a nice easy to understand graph over period of time.

How To: Upgrade Red Hat Enterprise Linux 5.3 to v5.4

nixCraft — Wed, 02 Sep 2009 18:22:59 +0000

Red Hat Enterprise Linux v5.4 has been released and available via RHN for immediate update. The new version includes the kernel-based virtual machine (KVM) virtualization, next generation of developer features and tools including GCC 4.4, a new malloc(). Also included clustered, high-availability filesystem to support Microsoft Windows storage needs on Red Hat Enterprise Linux.

Dell Says Linux Netbook Returns A Non-Issue

nixCraft — Thu, 13 Aug 2009 06:59:43 +0000

Microsoft chief operating officer Kevin Turner recently talked about netbook and claimed that retailers experiencing higher return rates as compare to MS-Windows operating systems:

And the reason that we were able to make so much traction - because this is the first real test of the value of Windows - the reason we were able to make so much traction on this particular space is because we went to retailers and said, "Hey, what are your return rates on these Linux netbooks that you are getting?" And they said, "Oh, gosh, they're, like, four or five times higher than what we're seeing on other PCs that have Windows." I said, "Exactly." So let's do the TCO story. Let's talk to customers. And you can't find a retailer - I challenge you to find a retailer who wants to sell Linux on these netbooks, because the returns are bad. The customer complaints are bad. And our ability to really showcase the value proposition with Windows has never been greater and was never tested more than it was with this particular product. But we've made great progress there, but the up-sell opportunities with Windows 7, because it runs so well on these low-end laptops, is going to be tremendous for us.

Vmware Linux Guest Add a New Hard Disk Without Rebooting Guest

nixCraft — Sat, 18 Jul 2009 06:55:53 +0000

As a system admin, I need to use additional hard drives for to provide more storage space or to separate system data from user data. This procedure, adding physical block devices to virtualized guests, describes how to add a hard drive on the host to a virtualized guest using VMWare software running Linux as guest.

It is possible to add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running Linux VM guest. This how to is tested under Vmware Server and Vmware Workstation v6.0 (but should work with older version too). All instructions are tested on RHEL, Fedora, CentOS and Ubuntu Linux guest / hosts operating systems.

6 Tools To Find Out Website Load Speed

nixCraft — Wed, 15 Jul 2009 17:42:34 +0000

Research shows that if your web pages take longer than 5 seconds to load, you lose 50% of your viewers and sales. As a UNIX admin often end users and web developers complain about website loading speed and timings. Usually, there is nothing wrong with my servers or server farm. Fancy java script and images / flash makes site pretty slow. These tools are useful to debug performance problems for sys admins, developers and end users. Here are six tools that can analyzes web pages and tells you why they are slow. Use the following tools to:

Make your site faster.
Debug site problem, especially client side and server side stuff.
Better user experience.
Improve the web.

Google Announces Linux Kernel Based Chrome OS

nixCraft — Wed, 08 Jul 2009 12:49:05 +0000

Google has announced Google Chrome OS, which should be available mid-2010. This is a direct challenge to MS Windows operating systems. This is excellent news and it is going to tied tightly to its Chrome Web browser. Google Chrome running within a new windowing system on top of a Linux kernel. Speed, simplicity and security are the key aspects of Google Chrome OS - said Sundar Pichai, VP Product Management, in a blog post.

Software Vs Hardware RAID

nixCraft — Tue, 07 Jul 2009 16:01:56 +0000

A redundant array of inexpensive disks (RAID) allows high levels of storage reliability. RAID is not a backup solution. It is used to improve disk I/O (performance) and reliability of your server or workstation. A RAID can be deployed using both software and hardware. But the real question is whether you should use a hardware RAID solution or a software RAID solution.

Increase Your VMware Virtual Hard Disk Size ( vmdk file )

nixCraft — Tue, 09 Jun 2009 14:22:42 +0000

I've Windows Vista installed as a guest under Ubuntu Linux using VMWARE Workstation 6.0. This is done for testing purpose and browsing a few site that only works with Internet Explorer. Since I only use it for testing I made 16GB for Vista and 5GB for CentOS and 5GB in size for FreeBSD guest operating systems. However, after some time I realized I'm running out of disk space under both CentOS and Vista. Adding a second hard drive under CentOS solved my problem as LVM was already in use. Unfortunately, I needed to double 32GB space without creating a new D: drive under Windows Vista. Here is a simple procedure to increase your Virtual machine's disk capacity by resizing vmware vmdk file.

Linux Find Out If PCI Hardware Supported or Not In The Current Running Kernel

nixCraft — Wed, 03 Jun 2009 15:05:04 +0000

From my mailbag:

How do I find out if a given PCI hardware is supported of by the current CentOS / Debian / RHEL / Fedora Linux kernel?

You can easily find out find out if a given piece of PCI hardware such as RAID, network, sound, graphics card is supported or not by the current Linux kernel using the following utilities under any Linux distributions.

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.

Poll: Common Causes Of Downtime In Your Data Center

nixCraft — Wed, 27 May 2009 14:42:27 +0000

Unplanned downtime may be the result of a software bug, human error, equipment failure, power failure, and much more. Last week was a bad one. We faced three different downtime:

First, there was a fiber cut for one of our data center resulting into routing anomalies due BGP reroute. Traffic was rerouted but updating those BGP tables took some time to update.
Someone from networking team failed to follow proper maintenance procedures for network device resulted into 55 minutes downtime.
One of our SAN hardware failure - Many internal UNIX / Linux web applications use SAN to store data including file server, tracking apps, R&D apps, IT help desk, LAN and WAN servers failed. This one lasted for 12 hrs. It was stared around midnight. The vendor replaced entire SAN hardware. Now we have dual stacked SAN as a backup device for internal usage.

Note: There is a poll embedded within this post, please visit the site to participate in this post's poll.

Lighttpd mod_rrdtool: Monitor The Load, Requests Per Seconds and Traffic

nixCraft — Sat, 23 May 2009 09:53:22 +0000

The round-robin database tool aims to handle time-series data like network bandwidth, temperatures, CPU load etc. The data gets stored in round-robin database so that system storage footprint remains constant over time. Lighttpd comes with mod_rrdtool to monitor the server load and other details. This is useful for debugging and tuning lighttpd / fastcgi server performance.

Linux HugeTLBfs: Improve MySQL Database Application Performance

nixCraft — Wed, 20 May 2009 07:59:39 +0000

Applications that perform a lot of memory accesses (several GBs) may obtain performance improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses. HugeTLBfs is memory management feature offered in Linux kernel, which is valuable for applications that use a large virtual address space. It is especially useful for database applications such as MySQL, Oracle and others. Other server software(s) that uses the prefork or similar (e.g. Apache web server) model will also benefit.

The CPU's Translation Lookaside Buffer (TLB) is a small cache used for storing virtual-to-physical mapping information. By using the TLB, a translation can be performed without referencing the in-memory page table entry that maps the virtual address. However, to keep translations as fast as possible, the TLB is usually small. It is not uncommon for large memory applications to exceed the mapping capacity of the TLB. Users can use the huge page support in Linux kernel by either using the mmap system call or standard SYSv shared memory system calls (shmget, shmat).

FreeBSD 7.2 Review: Improved Virtualization

nixCraft — Sat, 02 May 2009 08:40:26 +0000

FreeBSD is just plain old good UNIX with rock solid networking stack. It is quite popular amongst hosting companies, ISPs, portals (such as Yahoo) and a few large financial institutions because of its reliability, robustness and performance.

A new version of the FreeBSD is scheduled for release next week (4-May-2009). A beta 2 was made available for download few weeks ago for final round of testing before the official launch.

Tips To Protect Linux Servers Physical Console Access

nixCraft — Thu, 12 Mar 2009 19:09:31 +0000

This is an user contributed article.

Linux computer console is a physical device to operate a computer / server. Here are few steps which, if taken, make it more difficult for an attacker to quickly modify a system from its console.

Security Through Obscurity: MAC Address Filtering ( Layer 2 Filtering )

nixCraft — Tue, 17 Feb 2009 18:37:21 +0000

MAC Filtering (layer 2 address filtering) refers to a security access control methodology whereby the 48-bit address assigned to each network card is used to determine access to the network. Iptables, pf, and IPFW can block a certain MAC address on a network, just like an IP. One can deny or allow from MAC address like 00:1e:2a:47:42:8d using open source firewalls. MAC address filtering is often used to secure LAN or wireless network / devices. Is this technique effective?

VMWare Remote Console Plug-in Unrecoverable Error: (mks)

nixCraft — Mon, 26 Jan 2009 20:43:31 +0000

I'm having some weird problem with Firefox 3.0.4 under Ubuntu Linux. My test server runs inside VMWare server version 2.0. It was working fine with my Laptop. But with my desktop it started to dump errors for me. when I try to open the console of a virtual machine I have following error:

FreeBSD 7.2RC Released

nixCraft — Sun, 25 Jan 2009 15:08:30 +0000

The second of two planned Release Candidates for the FreeBSD 7.2-RELEASE cycle is now available. ISO images for Tier-1 architectures are now available on most of the FreeBSD mirror sites. The freebsd-update(8) utility supports binary upgrades of i386 and amd64 systems running earlier FreeBSD releases. Systems running 7.0-RELEASE, 7.1-RELEASE, 7.2-BETA1, or 7.2-RC1 can upgrade as [...]

Leap Second To Be Added End Of 2008 And Its Impact On Clustered Computers / Network

nixCraft — Wed, 31 Dec 2008 20:28:25 +0000

Get ready for a minute with 61 seconds. Scientists are delaying the start of 2009 by the first 'leap second' a timing tweak meant to make up for changes in the Earth's rotation.

The aged Earth is slowing down in its daily rotation, at least in the current epoch. So a leap second is added (a one-second adjustment added) to our time. This year will be exactly one second longer.

Precise time measurements are needed for high-speed communications systems among other modern technologies such as clusters, GPS, networks. You need to make sure that you are running updated version of ntpd that support leap second for UNIX and Windows computers.

How To Convert From a VMware Image To Virtualbox Image

nixCraft — Mon, 22 Dec 2008 20:24:43 +0000

VirtualBox is a virtual emulator like VMWare workstation. It has many of the features VMWare has, as well as some of its own.

I really like new Opensource VirtualBox from Sun. It is light on resources. Here is a quick tip - you can convert a VMware virtual machine (image) to a VirtualBox machine (image) using qemu-img utility, without reinstalling the GUEST operating system