Unix Operating System Tutorials

UNIX operating system articles, tutorials and resources
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APTonCD is a tool with a graphical interface which allows you to create one or more CDs or DVDs (you choose the type of media) with all of the packages you've downloaded via APT-GET or APTITUDE, creating a removable repository that you can use on other computers.One thing you need to remember this...
As the title suggests it is continuation of Basics of CrackMe With Sample and Example. I assume a working knowledge of GDB and ASM as basics. In this article we'll be cracking a simple application that is more advanced to the previous one.. In this article I take the cracking a step further by...
SSH is a abbreviation for Secure Shell is a network protocol that allows data-exchange between devices on the network..This is mainly used in linux OS's to access shell accounts , shell commands etc... SSH was mainly designed as a replacement modification to telnet etc..other insecure remote shells...
Cron is a Unix/Linux etc .. utility thaat allows the tasks to be run at specific time as well as at specific intervals..The job that the program does are know as CronJobs and are stored in a table (Cron Table).. Using To schedule any task with cron we can use crontab command in Unix.. Lets...
lsof or LiS Open Files is a very powerful command available on most of Unix-like systems, it lists all open files (in *nix everything is a file, drives, sockets, inodes, etc.). The listing can filtered using various parameters like process id, owner of the process, etc. In this article we'll...
Regular expressions commonly known as ‘regex’ provide an abstract and Flexible means to compare strings. It’s mainly used for scrapping and extraction of useful data from strings. In this tutorial we’ll be looking at some regular expressions using grep in Unix/Linux and how to use them in...
tee command is common on Unix like systems and on Windows PowerShell. The tee command writes the input to the file specified and also to the standard output, it was named after the plumbing T-splitter used. Here's a graphical presentation of the tee command: ...
1. What Is Kernel? A kernel is a central component of an operating system. It acts as an interface between the user applications and the hardware. The sole aim of the kernel is to manage the communication between the software (user level applications) and the hardware (CPU, disk memory etc). The...
Netcat (also known as ‘nc’ or ‘Swiss Army knife’) is a networking utility used for reading or writing from TCP and UDP sockets using an easy interface. NetCat is designed as a Dependable ‘back-end’ device that can be used directly or easily driven by other programs and scripts. Netcat is a treat to...
Introduction Many times we write programs which runs many instances of itself, either while using fork or we manually run many copies of the same program, so during the development stage we may need to kill all running instances and modify the program and re-run, or there may be other situations...
Concept: The UNIX kernel can keep track of many processes at once, dividing its time between the jobs submitted to it. Each process submitted to the kernel is given a unique process ID. Single-tasking operating systems, like DOS, or the Macintosh System, can only perform one job at a time. A...
Most sys admins know the importance of keeping an action log where various tasks, configuration changes, etc. are kept. Simple logs indicating, "I did this" or "John did that" may be sufficient in some organizations, but for some, full transcripts of changes made are desired. Doing a copy-and-paste...
Byte ordering in memory refers to the way in which the bytes corresponding to a certain value is stored in the memory. There are two ways in which bytes are stored in memory : Big endian Little endian Lets understand them one by one : Big endian
There are times, when sitting on your Linux box, working on a command line terminal, you suddenly feel a need of copying a file to/from a remote host. At this point you desire a command line utility that could do this task for you in just one line. Well, this is where 'scp' saves your day :-) ...
What Unix / Linux File Permission is? Every File or directory in the Linux Operating system has an access level which specifies the group or the users can actually access it. Linux Provides us with mainly 3 access levels for each user group i.e. Read , Write and Execute. These permissions can be...
xargs is an utility which is used to build & execute command-lines. xargs reads from the standard input (STDIN) space, tab, newline & end-of-file (EOF) delimited strings and executes the specified utility with the strings as argument(s). Most utilities/systems have a limit on the maximum no. of...
du is an abbreviation for (Disk Usage), this command calculates & returns the size of entire directory tree as well as of individual files. df is an abbreviation for (Disk Free), it's job is to calculate and return the amount of free space of a disk/partition. These two commands report space...
The GNU/Linux screen program is quite unknown, except for geeks & *nix experts, it helps you create multiple terminal sessions from a single one and lets you detach from the screen, at the same time maintaining the sessions as if you had never left the session and you can attach/connect to the...
Normally web traffic (HTTP) is unencrypted i.e. it's passed around the network in plain text, so anyone with the right tools can view what's being transmitted. This is okay generally, but when we pass sensitive information like credit card information, passwords, nowadays even personal information...
Now let us try to do same in Unix as we have discussed in the following Article - Splitting String Using Delimiter in Oracle In Unix it is pretty simple. We can use below commands to split echo "GO 4 EXPERT|99999|20130101|20131231"|cut -f1 -d"|" or echo "GO 4...