SSH is a popular cryptographic network protocol for secure network service operation. It is frequently used in remote server login. For a system administrator or software developer, SSH is frequently used to access remote servers or development servers or testing servers etc. To login with SSH, there are different authentication mechanisms : password, public key and interactive etc. If a remote server needs to be accessed frequently, password authentication may be too troublesome as password needs to be typed every time. In this scenario, public key authentication would be a life sav...

ext3 is a journaled file system that is commonly used by the Linux kernel. It is the default file system for many popular Linux distributions, including Debian. Stephen Tweedie. On June 28, 2006, Theodore Ts'o, the principal developer of ext3, announced an enhanced version, called ext4. Today, we will show how to convert ext3 to ext4 format on CentOS.System environment:Release version : CentOS release 5.4(Final)Kernel:  Linux localhost.localdomain 2.6.18-164.el5 #1 SMP Thu Sep 3 03:28:30 EDT 2009 x86_64 x86_64 x86_64 GNU/LinuxAssume the pa...

Greg Kroah-Hartman has released long-term kernel 3.0.20 and stable kernel 3.2.5. Both contain just a single bug fix that allows PCIe power-saving technology ASPM (Active State Power Management) to be used on systems with a BIOS that activates ASPM on some components, but states in the FADT (Fixed ACPI Description Table) consulted by Linux that ASPM is not supported. According to Matthew Garrett, who developed the patch, the change can reduce the power consumption of a Thinkpad X220 by 5 watts. The H's associates at c't magazine in Germany tested systems in their laboratory and experienced...

Environment : CentOS 5.3 x86_64, /dev/sdb1 is the data segment /data0. EXT3 file system.Problem : /data0/tcsql/cankao/phpcws-1.5.0/httpcws.cpp is deleted mistakenly and httpcws.cpp is not backed up. It will take much time to rewrite this program again. So we must recover it back.debugfs is feasible in EXT2 file system, but in EXT3 file system, it's not very useful. There is one open source software called ext3grep which can help us recover deleted file in EXT3 file system. The recovery steps are:1. Install ext3grep.wget http://ext3grep.googlecode.com/files/ext3grep-0.10.1.tar.gztar zxvf ext3gr...

It's very common that we need to transfer files between two different hosts such as backups. It is also an very simple task, we can use scp or rsync to complete the task well. But what if the file is very big, it may take some time to transfer it. How can we transfer a big file with high speed? Here we propose one solution.Copy fileIf we copy one uncompressed file, then we should follow below steps:Compress dataSend it to another hostUncompress the dataVerify the data integrityThis will be very efficient and it also saves bandwidth.With ZIP+SCPWe can combine ZIP and SCP to achieve this.gzip -c...

Last night, the 2013 Microsoft Build Developer Conference started in San Francisco. The highlight of the first day is Microsoft CEO Steve Ballmer announced the release of Windows 8.1 Preview . The final version will be released in November and he also mentioned that there would be over 300 updates on the new OS.Now let's summarize 10 major updates of the new OS.1. Classical desktop modeAfter getting a lot of feedback from users, Microsoft adds a new setting. Users can choose to start in classical desktop mode instead of the touch screen like in Windows 8 when the computer boots up.2. Apps auto...

Apache Superset (incubating) is a modern, enterprise-ready business intelligence web application. Compared with business-focused BI tool like Tableau, superset is more technology-navy. It supports more types of visualization and able to work in distributed manner to boost the query performance. Most importantly, it is free of charge!An example dashboard:Let’s go and set it up.Create a virtualenvAssume Anaconda is installed for python management.# create a virtualenv with python 3.6conda create -n superset python=3.6Install in virtualenventer the virtual environment and follow the of...

IE won the browser war before Chrome appeared with the help of anti-competitive practices. But with the appearance of more and more easy-to-use and fast browsers, people start to hate IE and leave IE. It seems IE is not a product of modern age. Do IE developers feel guilty about this?Everything is contextual. The browser that most people hate today is IE6, which, at the time was one of the best browsers on the planet (it didn't win the Browser Wars, Round One, by accident). It was built on "internet-time" before a lot of the security issues it suffered from were even well-understood in the ind...