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…
Compression is a simple way to speed up the site. PHP’s gzip compression is excellent. And using it is very convenient: Simply put these codes before any HTML content at the beginning of the PHP script: <?php if (substr_count($_SERVER[‘HTTP_ACCEPT_ENCODING’], ‘gzip’)) ob_start(“ob_gzhandler”); else ob_start(); ?> In WordPress, the suitable position for these codes is the beginning…
I prefer putting pages that contains all the categories, archives and even all the posts in one page to putting these links in the side bar. Actually, most of time it needn’t to stay on every pages. And if it is in the side bar, the search engine will see these links in every page…
With a list of servers, it is common that one or more are down or crash. Lots cluster management tools can detect the aliveness of servers. However, it can be easily done with ping with a Bash script. I summarize the script that I used and share it here: check-alive-server.sh. Usage: usage: ./check-alive-server.sh file Each…
Shutting down servers is a common operations for managing a cluster. However, if this server is configured to a Xen Dom0 and has Xen VMs (DomUs), the VMs should be shutdown first to avoid data lost on these VMs. xm supports a -a option to shutdown all VMs: # xm shutdown -a Add the -w…
I frequently run some commands/scripts on a batch of servers whose IPs are already collected in a file. I usually use a simple loop and call the ssh to run these commands remotely and automatically. This operation, however, is common and can be abstracted into a separate script. Here is the script that I come…
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…
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…
The new development of Xen and Linux kernel make it easy to install Xen on Fedora as the Domain-0 now. This post uses Fedora 17 as an example platform to introduce how to set up Domain-0 on Fedora Linux. Compared to our old method (https://www.systutorials.com/setting-up-stable-xen-dom0-with-fedora-xen-3-4-3-with-xenified-linux-kernel-2-6-32-13-in-fedora-12/) which requires manually compiled Xen and patched kernel, the current…
Linux booting is usually controlled by Grub or the new Grub2. Setting the default booting entry is a frequent operations. Here, we introduce how to set the default entry in Grub2 and Grub. Setting the default booting entry in grub2 Note1: With some version of grub2, the grub2-set-default method and the script below may not…
Vim is my favourite text editor and I also prefer to use Vim to compose Email. I ever used Vim as Thunderbird’s External editor with the help of plugin. I started to use KMail as my email client on KDE and I find it is not hard to configure KMail to use Vim as email…
We usually have video files in .wmv .mpg .rmvb or .mkv formats. The iPod, iPhone or iPad only accept a limited number of video file types, such as .mov and .mp4. To play these video files in .wmv .mpg or .rmvb format, we should first convert them to .mov or .mp4 files that can played…
The latest tools for upgrading Fedora is FedUp, please check How to upgrade Fedora 19 to Fedora 20 through the network. Please consider PreUpgrade for upgrading Fedora. This is the recommended method. This post makes a list of actions should be done to upgrade Fedora using yum. Please note that this is for experienced users…
Vim is an excellent editor which I use every day. Thunderbird is a nice email application. However, Thunderbird’s integrated editor is not efficient enough to a Vim user. Why not use Vim as Thunderbird’s editor? In this tutorial, we will introduce how to integrate Vim with Thunderbird together in Linux. Install the “External Editor” Thunderbird…
LVM’s snapshot feature enables us to duplicate an LVM backed Xen DomU in seconds rather than minutes. We no longer need to copy the entire file system image like backing up file backed Xen DomU. We just need to make a snapshot of the current Xen DomU in seconds. When there are changes to the…
LVM’s snapshot feature enables us to duplicate an LVM backed Xen DomU in seconds inside of the same volume group. When we want to duplicate LVM backed Xen DomU from a remote server, we need to make use of LVM’s snapshot function and tools like scp and dd. Backing up the DomU is only part…
This is the latest stable and recommended stable Xen Dom0 solution on Fedora 12. No serious bug found till now and we will fix the bugs by ourselves if some appears. It also works on Fedora 14 as well. It should not be hard to use this solution on other versions of Fedora or other…
I don’t use xdm, gdm or kdm… I prefer my Linux booting to init 3. I like logging in to the command-prompt and starting X manually with startx. In my Fedora Linux box, I always get to gnome even both gnome and KDE are installed. Actually the startx script is already written for most of…
How to set up eCryptFS in Linux will be introduced in this post. We can store encrypted files in one eCryptFS directory, the manual way. The content can be seen only after it is mounted as eCryptFS file system. Otherwise, the users can only see garbled characters in the files. Note that this tutorial will…
The heirloom mailx (or s-nail if you are using Ubuntu 18 or later or similar releases) command in Linux is still providing service for guys like me, especially when we need to send email automatically by script. Gmail is great. Now, how to use gmail’s smtp in mailx/mail? gmail is a little special since gmail’s…