(Written by Ping Lee, Henry Chuang, Charlotte Yaou, Winson Chao, and Gary Hsueh)
To get the most from the article, you should have a basic knowledge of SNORT, Linux and a working Linux system on which you can practice the commands covered in this article. Also you should have some networking knowledge such as TCP/IP, iptables, etc.
What Is IPS (Intrusion Prevention System)?
Intrusion Detection System (IDS) is a device which monitors packets on your network. IDS reports attack behaviors based on security... [More]
Suppose you have a query related to some thing on Linux and you ask an expert sitting at a remote end. The expert cross questions and enquires about the Linux kernel release that you are using. Well. sometimes you get stuck as you don't know where to search for kernel release in Linux. What if you knew a Linux command that can provide most of your system related information quickly? So, In this article, we will discuss the Linux 'uname' command (through examples) that serves exactly the same purpose.
The syntax of uname... [More]
The netstat command in Linux is a very useful tool when dealing with networking issues. This command is capable of producing information related to network connections, routing tables, interface statistics etc. This utility also helps the network administrators to keep an eye on the invalid or suspicious network connections. In this article we will understand the basics of this command using some practical examples.
The syntax of this command is :
1. Display routing information maintained by kernel... [More]
Just came across this video on one of the video sharing websites. The statistics presented in this video reflect the amazing speed at which Linux is developed and huge scale at which it is being used or deployed across the devices in real world. It's an beautifully crafted video which every Linux enthusiast should watch. So, just wanted to share it...
Have you ever thought what happens behind the doors when a user login happens in Linux? Where is the login information for a user is kept in Linux and how the validation of user credential takes place? Well, if not, then I would suggest you to read on as in this article we will discuss how user login management and validation takes place in Linux.
The /etc/passwd file
Well, this is the file in Linux system that contains all the relevant information related to user login. If we peek inside this file, this is what it looks like on my... [More]
As a Linux user, sometimes it is required to know some basic information like :
Time of last system boot List of users logged-in Current run level etc Though this type of information can be obtained from various files in the Linux system but there is a command line utility 'who' that does exactly the same for you. In this article, we will discuss the capabilities and features provided by the 'who' command.
The basic syntax of the who command is :
who [OPTION]... [ FILE | ARG1 ARG2 ]
Examples of 'who' command
1. Get... [More]
Any application running on Linux may request services like :
Inter process communication I/O services Creating a new process Accessing system hardware etc
Note: The above list is not exhaustive.
The services listed above are all handled by Linux kernel. So, any application in Linux that requires any of these services has to request the Linux kernel to handle the request on its behalf. The request is handed over to kernel by calling corresponding system calls. System calls act as an interface between application and kernel.
The Linux command 'stat' is used for displaying status information of Linux files and file systems. In this article, we will discuss the usage of stat command with examples.
stat command syntax
The syntax of stat command is :
stat [OPTION]... FILE...
stat command examples
1. A basic example
In the simplest form, the stat command can be used by supplying a file name as an argument :
$ stat testdisk.log
Size: 1014 Blocks: 8 IO Block: 4096 regular file
Device: 805h/2053d Inode:... [More]
Many software engineering activities rely on the automated support afforded by tools. In order to maximize their benefits, they are often retrofitted to development environments that enable them to capitalize on facilities provided by compilers, debuggers, and profilers. In this context, focusing on the integration of a set of mainstream C/C++ development tools (Valgrind, OProfile, Autotools, perf, among others) along with several in-house IBM ones (Advance Toolchain, FDPR, and others), we have used Eclipse as a basis to bring together a SDK... [More]
A Process is one of the most important fundamental concepts of the Linux operating system. This article focuses on the basics of Linux processes.
A process is an instance of a program running in Linux. This is the basic definition that you might have heard before. Though its simple enough to understand but still lets elaborate a bit for the beginners.
Lets quickly create a hello world program in C language :
printf("\n Hello World\n");
// Simulate a... [More]
In this article we will study about the Linux open() system call that opens a file (or device). This system call can also be used for creating a file before opening it.
The prototype of the open() function is :
int open(const char *pathname, int flags);
int open(const char *pathname, int flags, mode_t mode);
The argument 'pathname' (as the name suggests) is the complete (or relative) path of the file on system.
Since there is also a cap on maximum length of a file name or maximum length of file path in Linux. So, lets say if the... [More]
Fetching the file system usage is a primary task while performing
maintenance of any OS. Various OS provide their own
tools/utilities/commands to fetch the file system usage. In Linux too
there exists a utility (df) that provides information on file system
usage. In this article, we will discuss the 'df' command
line utility with practical examples.
Before jumping to examples, lets quickly go through the description of
this command through man page.
DESCRIPTION This manual page documents the GNU version of df.... [More]
There are times when you would want to kill a process due to the
any reason like its high CPU usage, high memory usage or simply you
believe that its a virus or a malware. There are various
commands/utilities available in Linux for doing this. One such command
is 'killall'. Lets discuss the 'killall' utility in this article
through some examples.
Before jumping on to the examples, lets briefly take a look at it s
description from the man page :
killall sends a signal to all processes running any of the... [More]
In the part -I ( here ) of this series, we understood the basic concept behind accessing and parsing the command line arguments in Linux. Also, we discussed a simple calculator program that parses the command line arguments and produces the output. In conclusion, we saw a glimpse of the standard 'getopt()' function that is mostly used for the parsing of command line arguments. In this part we will discuss the 'getopt()' function to understand its importance and how is it used. First we will understand the theory behind this function and then we... [More]
Configuring and administrating Linux by using command line utilities is the most popular and preferred way. If you have ever used Linux for your personal or professional work, you would have definitely used the command line.For example, to check the contents of a directory, most users prefer using the 'ls' command rather using the GUI. Most of these command line utilities are written in 'C' language and accept flags and arguments for accepting inputs from user.
For example :
The output of 'ls' command (for a... [More]