How to convert TIFF files to PDF format on Linux

TIFF (Tagged Image File Format) is a popular image file format. Unlike other types of image files, a TIFF file can contain multiple images (e.g., multi-page document scan) in it. TIFF editor software such as GIMP is able to support such multi-page TIFF files. If you would like to convert a TIFF file to PDF format on Linux, you can follow the instructions below.Read more »

How to reboot automatically after kernel panic

There are cases where you encounter kernel panic. Kernel panic may occur while you are playing with some experimental kernel module that someone else wrote, or developing a custom kernel module yourself. Kernel panic can happen due to hardware failure as well. If you would like to reboot your system automatically after kernel panic has occurred, there are three different ways to do it.Read more »

How to convert xlsx files to xls or csv format on Linux

The xlsx file name extension is a new file format based on XML, used by Microsoft Office Excel 2007 spreadsheet application. The letter "x" appended to the existing "xls" extension used by earlier versions of Excel, signifies that the format is based on XML. If you would like to open or edit an xlsx file created by Excel 2007, on an earlier version of Excel or any other spreadsheet application, you need to convert xlsx files first.Read more »

How to allow remote access to MySQL server

If you have installed MySQL fresh (e.g., "sudo apt-get install mysql-server" on Debian/Ubuntu, and "sudo yum install mysql-server mysql" on CentOS/Fedora/RedHat), MySQL server binds on local loopback address (i.e., 127.0.0.1) by default. This means that you can access MySQL server only from the local host, but not from any remote host. You can verify this by running netstat as follows.Read more »

How to edit a PDF file for free

pdftk (PDF Toolkit) is a command-line tool which enables you to edit PDF files. pdftk is freely available on Linux, MS Windows, MacOS X and FreeBSD. So using pdftk, you can edit PDF files for free. If you would like to install pdftk on Linux, proceed as follows.Read more »

How to mount HDFS using FUSE

Hadoop Distributed File System (HDFS) is a distributed, scalable filesystem developed as the back-end storage for data-intensive Hadoop applications. As such, HDFS was designed to handle very large files with "write-once-read-many" access model. Not being a full-fledged POSIX compliant filesystem, HDFS cannot be directly mounted by the operating system, and file accesses with HDFS are done via HDFS shell commands.Read more »

How to install SSH on Linux

Secure shell (SSH) is a network prototol providing shell services on a remote machine via a secure channel. OpenSSH is an open-source implementation of the SSH protocol, allowing encrypted communication over a network via a suite of software. If you would like to set up SSH on Linux, you can install OpenSSH as follows.Read more »

How to install GNOME desktop on CentOS

Suppose you have set up a "minimal" version of CentOS without X-windows on your machine before. Now you wish to install GNOME desktop on the CentOS system in order to run some desktop applications. If you would like to add GNOME desktop to CentOS minimal installation, you can do the following.Read more »

How to add an additional hard drive to Xen VM

There are cases where you would like to add an additional disk to a Xen guest VM, and make the newly added storage available to the VM. In order to add an additional hard drive to Xen VM, do the following.Read more »

How to disable SELinux

Security-Enhanced Linux (SELinux) is a set of kernel enhancements and user-space tools to enforce mandatory access control and security policies. When SELinux is enabled on your system, there may be cases where you would like to turn off SELinux temporarily, for example when you are experimenting with Apache or NFS server, and SELinux gets in the way, blocking necessary port access.Read more »

How to find and kill zombie processes on Linux

A process is called a zombie process if the process has been completed, but its PID and process entry remains in the Linux process table. A process is removed from the process table when the process is completed, and its parent process reads the completed process' exit status by using the wait() system call. If a parent process fails to call wait() for whatever reason, its child process will be left in the process table, becoming a zombie.Read more »

How to find the number of CPU cores on Linux

Multi-core CPU processors are common nowadays, including dual-core processors (e.g., Intel Core Duo), quad-core processors (e.g., Intel Core i5), and hexa-core processors (e.g., AMD Phenom II X6). Also, many server-grade physical machines are equipped with more than one CPU processor. In order to find the number CPUs, and the number of cores per CPU, you can refer to /proc/cpuinfo.Read more »