It is common to execute commands on many nodes/hosts via SSH for managing a cluster of Linux servers. On Linux, there are many choices for this task. Generally, to run commands on many nodes, there are two modes: serial mode and parallel mode. In serial mode, the command is executed on the node one by…
Linux is a great platform for software development targeting servers or backends. In general, working on Linux is very productive. The problem that beginners on Linux face is the the learning curve is steep at the beginning. But believe me, after you get through the initial green steep learning step as in the figure below…
Doing actions upon changes of files and directories is very useful. Examples like compiling a project after the source code files are changed, sending emails after important configuration files are modified, building the PDF after a TeX file is modified. On Linux, the inotify-tools provide good support for trigger actions after changes. In this post,…
Vim is pretty fast and powerful. However, the core of Vim is (yet) single-threaded (some discussions and tries on porting Vim to be multi-threading, but not yet there). This means some functions that are slow will block Vim there and you have to wait for it. While Vim is fast, some plugins are not. When…
Having to go the the server room to reset servers is the most headache thing for admins managing a cluster of Linux servers in a remote site. Either you can ping the server but can not ssh to it, or you even can not ping it. There are various reasons that may cause a Linux…
Hadoop 2 or YARN is the new version of Hadoop. It adds the yarn resource manager in addition to the HDFS and MapReduce components. Hadoop MapReduce is a programming model and software framework for writing applications, which is an open-source variant of MapReduce designed and implemented by Google initially for processing and generating large data…
Update on Oct. 9, 2014: You should be aware of the possible security problems of blowfish and it is suggested not to be used. Instead, you may consider ChaCha20 as suggested by Tony Arcieri. To use this with OpenSSH, you need to specify the Ciphers in your .ssh/config files as chacha20-poly1305@openssh.com possibly with another default…
I use Emacs in terminals and start/close Emacs frequently as needed like in a file checking-editing-closing loop. However, Emacs seems take some time to start up especially some heavy modes are used. How to make Emacs start up faster? (If you just want the solution/script first, find the command in the summary section.) My solution…
Gnome 3 is great and I can understand that it emphasizes on simplicity. However, the configuration settings for Gnome 3 does not provide tools for certain functions that I need. One of them is customizing the fonts. This post will summarize the tools/tips that I adopted to customize the fonts in Gnome 3. Usually, the…
Vim is a fast and handy editor on *nix systems. Like Emacs, Vim has a steep learning curve as you get constantly get new things. However, the effort deserves it as you efficiency is highly improved. Here, I summarize the tips and howtos I learned using Vim. Some previous posts on vim are tagged with…
I ever introduced seting up git server using SSH or gitosis. However, gitolite is the way to go for managing git servers if you want an lightweight authentication layer. gitolite provides many very usefull features which can control each user’s right on each branch. I set up one gitolite git server and am very happy…
Software you will need 1, Putty 2, Real VNC viewer 3, twm (lightweight desktop). On fedora (centos, redhat): sudo yum install twm (on other distros, you may need other commands, or download source code and install it). Specific steps 1, Enter your Host name and port in putty. 2, Set port forwarding in putty Tunnels….
Update on Nov. 18, 2012: ATI fglrx driver works well on Fedora 17 with GNOME 3 Shell. Should work well with later releases. Great driver, ATI! Update on Nov. 29, 2011: ATI fglrx driver works on Fedora 16 with GNOME 3 Shell with Catalyst driver 11.11 (xorg-x11-drv-catalyst-11.11). Update on Oct. 9, 2011: GNOME 3 shell…
xclip is a tool to copy the copy the output of commands from a command line in a terminal to X selection or clipboard. It connects the command line interface and the X selections (clipboard) and is a very useful tool. For example, processing some text in vim in a terminal and then copying it…
Automatic keyboard pressers are useful tools. However, it seems that there is no simple and easy to use automatic keyboard presser for Linux if you search for “automatic keyboard presser linux”. After some digging, I find using the xvkbd with some options is a good method for automatic keyboard pressing though it is not designed…
Integers are natively supported in Bash shell. However, what if we use floating point in Bash shell? The short and direct answer is using ‘bc‘ command – “An arbitrary precision calculator language.” Just run bc and enter some floating point calculation expression, such as “1.2+8.2”, bc will give the result. In a script, we certainly…
With Emacs, I feel happy. I love the rich functions of Emacs, such as compiling, quickly jumping to the lines with compilation error and debugging with gdb, and more. I ever wrote small tips posts about Emacs before. But it is a good idea to put them together and keep adding new ones. Here comes…
iptables is a mechanism in Linux kernel for port forwarding, NAT, firewalls etc. In Linux distros, such as Fedora, the iptables is configured to be as a “strict” firewall that opens a limited know ports, such as 22 for SSH. However, in some network environment, such as a private cluster, the nodes are trusted and…
I ever discussed Starting KDE from Command Line by startx for KDE and GNOME. Recently, I installed MATE desktop on Fedora 17 and am very happy with it—dear, Gnome 2 is back. However, I checked the /etc/X11/xinit/Xclients script which is called by ‘startx’ and it only includes ‘startkde’ and ‘gnome-session’ without support to MATE. But…
Copying some text to a new file is a common operation on Linux. I usually do this by opening the file with ‘vim’, pasting the text in ‘vim’, and then saving the file. I learned a more efficient and quicker way from my advisor during one discussion with him when I show him some results….