Lan Vu's Blog

Linux shell scripting: /bin/sh : bad interpreter: No such file or directory

lanvu — Fri, 06 Jan 2012 18:57:03 +0000

I usually get the below message when creating a Linux shell script with text editors like Notepad or Wordpad on Windows PC and executing it on Linux box:

“: /path/to/scriptfile:/bin/sh^M: bad interpreter: No such file or directory”

The top of the script is a line specifying the shell program by which the script is interpreted:

#!/bin/sh

Double-check if there is any typo in the script file or the /bin/sh exists on the Linux machine. It sounds like everything is OK. Now, I am sure the error caused by the text editor used to create the script file. In fact, text editors of different platforms like Mac, PC, Linux can create text files with different formats and this is the reason of the error. In our case, line ending characters by the text editor on Windows are different from the ones on Linux which cause the shell scripted not be interpreted in a right way. To fix the error, do following steps at Linux command line:

Open the script using vi program

vi /path/to/scriptfile

When file is opened, change the format of the script to the right one by entering

: set fileformat=unix

Finally, save the script for the new format taking effect and exit the vi program by entering

: x

Now, the script is working fine without any error. An easy way this avoid this problem is creating scripts directly on Linux with vi program.

Please note that using text files of another operating system on Linux may result in similar problems. For example, some errors when compiling your source code files or a program can not read data text files. These problems can be solved using the solution in this post.

How to fix: locate: can not open `/var/lib/mlocate/mlocate.db’: No such file or directory

lanvu — Fri, 12 Aug 2011 17:45:54 +0000

You got the message “locate: can not open `/var/lib/mlocate/mlocate.db’: No such file or directory” when using locate command ?

To fix it just simply use updatedb command.

For example:

[root@xyz ]# locate lan.vu

[root@xyz ]# locate: can not open `/var/lib/mlocate/mlocate.db’: No such file or directory

[root@xyz ]# updatedb

[root@xyz ]# locate lan.vu

/home/lan.vu

CPU affinitity – Why need and How to ?

lanvu — Fri, 05 Aug 2011 20:40:32 +0000

CPU affinity ( or processor affinity ) is an ability provided by operating systems such as Windows or Linux that allows you to select specific CPUs or processors to run your program/application on. In a multi-core and multi-processor system, the assignment of a process to a CPU/processor is automatically decided by the OS via its scheduler. However, you still can interfere in this scheduling task by specifying a CPU that your program will be run on.

Why CPU affinity is needed ?

You may ask “Why do I need it if OS is hanlding everything for me?”. You are right. In most cases, you won’t need this function. However, if the runtime performance is your concern, in some cases, it’s worth a try to decide whether to use CPU affinity. For demonstration, I wrote a simple parallel program doing some computations using multi-cores. When I ran this program on a 12-core machine (two prossesors , six cores per processor) with/without CPU affinity, I got below runtime performance.

CPU affinity improves the runtime performance because it optimizes cache performance by reducing cache miss. In a NUMA system, setting CPU affinity and allocating memory also on the faster RAM can speed up the process as well.

How to ?

There are two ways to set the CPU affinity in both Linux and Windows.

In Windows:
Method 1: Set the CPU affinity using Task manager

Open Task manager by pressing Ctrl + Alt + Delete and selecting the Task manager
Select Processes tab
Right click on the process that you want to set CPU affinity
Select “Set affinity…” from the drop down menu
Set the CPUs that you want your program to run on

Method 2: Second, program from your source code
You can use the Windows API SetProcessAffinityMask to set the CPU affinity from your program code

In Linux:

Method 1: Launch the program from the command line using settask
The below command will launch gedit in CPU 1 & 4 (or 0 and 3).

taskset -c 0,3 gedit

Method 2: Second, program from your source code
You can use the function sched_setaffinity in sched.h to manage CPU affinity from your code

Fix the error ” make: execvp: Permission denied “

lanvu — Fri, 05 Aug 2011 19:23:01 +0000

” make: execvp: : Permission denied … “

You got this error message? In my case, I got this message when trying to compile a software in my Linux box. To fix this issue, just simply change file access permissions using chmod command.

$ chmod 755 /path/to/yourfile

If you want to change file access permissions for a folder and all files in that folder, you can add the -R option to the chmod command

$ chmod 755 -R /path/to/yourfolder

Revolution Analytics and Zementis Deliver Decision Engine for R

lanvu — Thu, 24 Feb 2011 14:21:03 +0000

PALO ALTO, Calif., Feb. 23 — Revolution Analytics, the leading commercial provider of R software, services and support, today announced a strategic partnership with Zementis, a leader in predictive analytics solutions. R data models developed on the company’s flagship product, Revolution R Enterprise, are now accessible through the Zementis ADAPA Decision Engine and cloud computing platform. The joint solution extends the reach of predictive analytics to key enterprise systems including Excel, CRM deployments, call center systems, online ad platforms and more – all in real-time. Using RevoDeployR, Revolution Analytics’ R-based web services framework, ADAPA can seamlessly deploy and score R data models.

“The ability to bring R into any business application in real-time is where the true value of predictive analytics is realized, ” said Michael Zeller, CEO of Zementis. “R is incredibly popular and our strategic partnership with Revolution Analytics stems from the company’s extensive ability to support commercial R. It also reinforces both companies’ dedication to bring advanced analytic capabilities and real-time operational insight to line-of-business users.”

AMD Intros OpenCL University Kit

lanvu — Thu, 24 Feb 2011 14:13:07 +0000

SUNNYVALE, Calif., Feb. 23 — AMD today announced the introduction of the OpenCL University Kit, a set of materials that can be leveraged by any university to assist them in teaching a semester course in OpenCL programming.

This effort underscores AMD’s commitment to the educational community, which currently includes a number of strategic research initiatives, to enable the next generation of software developers and programmers with the knowledge needed to lead the era of heterogeneous computing. OpenCL, the only non-proprietary industry standard available today for true heterogeneous computing, helps developers to harness the full compute power of both the CPU and GPU to create innovative applications for vivid computing experiences.

Web Experts Ask Scientists to Use the Web to Improve Understanding, Sharing of Their Data

lanvu — Thu, 24 Feb 2011 14:03:12 +0000

Feb. 14 — Peter Fox and James Hendler of Rensselaer Polytechnic Institute are calling for scientists to take a few tips from the users of the World Wide Web when presenting their data to the public and other scientists in the Feb. 11 issue of Science magazine. Fox and Hendler, both professors within the Tetherless World Research Constellation at Rensselaer, outline a new vision for the visualization of scientific data in a perspective piece titled “Changing the Equation on Scientific Data Visualization.”

As the researchers explain, visualizations provide a means to enable the understanding of complex data. The problem with the current use of visualization in the scientific community, according to Fox and Hendler, is that when visualizations are actually included by scientists, they are often an end product of research used to simply illustrate the results and are inconsistently incorporated into the entire scientific process. Their visualizations are also static and cannot be easily updated or modified when new information arises.

How to make voice calls on Samsung Galaxy Tab

lanvu — Wed, 09 Feb 2011 18:18:52 +0000

The Samsung Galaxy Tab was launched in Nov 2010 and considered as the iPad killer. In general view, this product has many features which are more powerful than iPad. Although few reviews show that the Samsung tablet performance can not compare to iPad, it is worth the price for lighter weight, smaller size, Flash support, front and back cameras and external storage support (micro SD cards) . I think this tablet is the combination of iPhone 4, iPad and Amazon Kindle. One of the most important features attracted me is the ability of a cell phone. Oh NO! This was my biggest illusion because all US versions of Samsung Galaxy Tab currently don’t support the voice calling; only text message and internet access work. But it doesn’t mater since you’re not going to hold this beast up to your head. Anyway, for anyone who love to use it as a real phone, we still have few alternative ways to make the voice calls.

Use Google Talk to make phone call (require wi-fi access)
Use Skype to make phone call (require wi-fi access)
Use other VoIP applications (require wi-fi access)
Hack it to enable the voice calling function. One solution can be found here. I did not try this method so I am not sure if it works.
Buy the European version of Samsung Galaxy Tab for the full voice calling function.
Waiting ! Samsung may change their mind and enable this feature in their newer versions.

I don’t know why Samsung had to disable this feature on US versions but the carriers may earn more contracts because of that. Below are some hardware specifications of Samsung Galaxy Tab

Android 2.2 running TouchWiz 3.0
7-inch TFT LCD with 1024 x 600 resolution (WSVGA)
Weighs 380 grams
1GHz Cortex A8 processor
16GB or 32GB internal storage
microSD expansion for up to 32GB additional storage
Front-facing 1.3 megapixel camera and rear 3 megapixel camera with flash
4,000mAh battery
3G data / voice (there’s a speakerphone and Bluetooth for phone calls, but no earpiece)
5GHz dual-band 802.11n WiFi
Standard back color is white, carriers might offer different colors
Full HD video playback
There’s a 30-pin dock connector on the bottom that allows for HDMI, USB, and docking accessories (a car dock at least is planned)

A review of Samsung Galaxy Tab vs. Apple iPad

For anyone who want to use it as a small laptop, you can buy a tablet case with bluetooth keyboard. These accessories will cost you about $50.

Bright Cluster Manager Added to Dell High Performance Computing Portfolio

lanvu — Mon, 07 Feb 2011 18:03:20 +0000

Bright Computing, a leader in cluster management software, today announced that Bright Cluster Manager is now available through Dell, Inc., as an option for High Performance Computing Clusters (HPCC). Bright Cluster Manager is already used to manage more than 50 Dell HPC installations worldwide, including three TOP500 supercomputing systems. Bright installations on Dell platforms comprise universities (Cambridge, Oxford, University of Houston, City University of New York and others); commercial enterprises (Merck, Saudi Aramco, Genus, CD-adapco and others); and various national laboratories, including the FutureGrid cluster at the Texas Advanced Computing Center (TACC). Further, Bright Cluster Manager is running on the Dell benchmark clusters, also located at TACC.

Microsoft wants Intel to build 16 core Atom chip

lanvu — Fri, 04 Feb 2011 23:14:23 +0000

Microsoft has asked Intel to develop a 16-core version of its low power Atom chip for use in servers, part of a wider effort to reduce power consumption in its massive data centres, a Microsoft executive said Thursday.

There’s a “huge opportunity” to improve energy efficiency by using servers based on small, low-power chip designs such as Intel’s Atom and Advanced Micro Devices’ Bobcat, said Dileep Bhandarkar, a distinguished engineer with Microsoft’s Global Foundation Services, which runs the company’s data centres.