Single-User mode is used for a system recovery. However, by default, no authentication is used if single-user mode is selected. This can be used to bypassing security on the server and gaining root access. To enable authentication for single-user mode, open the /etc/inittab, file: # vi /etc/inittab Add the following line to the...

By default, when we are creating new user to Linux OS, all files from /etc/skel are copied to the new user's home directory. There are few files included in /etc/skel/ by default. * /etc/skel/.bash_logout * /etc/skel/.bashrc * /etc/skel/.profile * /etc/skel/.cshrc If you want to share some files, including rules and regulations to new users, simply add it...

Do you want to Download your favorite you tube video in Linux? No problem! Here I have mentioned all steps to download you tube video using Linux Terminal.   Step 1: Install youtube-dl package by executing, On Ubuntu, $ sudo apt-get install youtube-dl On Fedora, RedHat, CentOS, # yum install youtube-dl -y Step 2: After having successfully installed youtube-dl, open a...

vm.swappiness is a tunable kernel parameter that controls how much the kernel favors swap over RAM. At the source code level, it’s also defined as the tendency to steal mapped memory. A high swappiness value means that the kernel will be more apt to unmap mapped pages. A low swappiness value means the opposite, the kernel will be less apt to unmap mapped pages. In other words, the higher the v...

When your system is rebooted, grub presents the boot option menu called splace screen. From here, you or anybody can easily login into a single user mode (sometimes it is called Rescue Mode) without the password which might result into breaching computer security. You can set a password for the GRUB boot loader. This prevents users from rescue or Singe-User  mode or changing settings at boot ...

memtester is a user-space utility for testing the memory subsystem in a computer to determine if it is faulty. It does a good job of finding intermittent faults and non-deterministic faults. It has many tests to help catch borderline memory. memtester should compile and run on any 32- or 64-bit Unix or Unix-like system. Download latest version of memtester from...

  This article will guide you through the necessary steps to install ipw3945 wireless adapter on a CentOS / RHEL based distribution. Before we start, make sure that you have rpmforge repository configured. If you do not have, download it from here. # wget http://packages.sw.be/rpmforge-release/rpmforge-release-0.5.2-2.el5.rf.i386.rpm # rpm -ivh...

Squid is a proxy server and web cache daemon. It has a wide variety of uses, from speeding up a web server by caching repeated requests; to caching web, DNS and other computer network lookups for a group of people sharing network resources; to aiding security by filtering traffic.  Once after you have configured Squid, you may notice at the bottom of error page signature appears with GMT timezone. You might...

vmstat reports  information about processes, memory, paging, block IO, traps, and cpu activity. The first report produced gives averages since the last reboot.   Additional  reports  give information on a sampling period of length delay. The process and memory reports are instantaneous in either case. [root@linuxArticles.org ~]# vmstat -s 4087800  total memory 1643176  used m...

Wireshark Network Analyzer is use full to track network packets. To sniff MySQL packets and decoding it, we will use mysqlsniffer. Note: This will not usually work for local connections. First, install libpcap-dev, which is the development library that allows an application to sniff network packets. $ sudo  apt-get install ...

You can easily block SSH server attacks including dictionary based attacks and brute force attacks using a Python based script - DenyHosts. It analyzes the sshd log messages to determine what hosts or IPs are attempting to hack into your system. STEP 1: Enable Rpmforge Repo in your system, For 32bit CentOS / RHEL Linux enter: # rpm -Uhv...

Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. As of October 2010, Firefox is the second most widely used browser, with 30% of worldwide usage share of web browsers. In Germany, Firefox is the most popular browser with 60% usage says Wikipedia. To install Firefox 4 on Fedora Linux, # vim ...

Ping is used to check how many systems are up. Most of the hackers are using ping for finding the hackable machine. The hacking chances can be reduced by turning off ping response. For RHEL/Cent OS/Fedora Linux, open terminal as a root and execute, # sysctl -a | grep icmp net.netfilter.nf_conntrack_icmp_timeout = 30 net.ipv4.icmp_echo_ignore_all =...

Fedora, CentOS and RHEL allow the console user to perform an interactive system start-up by pressing [I] key. Using interactive boot, attacker can disable the security services and may get access to system. Open etc/sysconfig/init file and disable PROMPT option, # vim /etc/sysconfig/init PROMPT=no Now restart the system and...

Rsync is a fast and extraordinarily versatile file copying tool. It can copy locally, to/from another host over any remote shell, or to/from a remote rsync daemon. It offers a large number of options that control every aspect of its behaviour and permit very flexible specification of the set of files to be copied. It is famous for its delta-transfer algorithm, which reduces the amount of data...

hdparm provides  a command line interface to various kernel interfaces supported by the Linux SATA/PATA/SAS "libata" subsystem and  the  older IDE driver subsystem.  Many newer (2008 and later) USB drive enclosures now also support "SAT" (SCSI-ATA Command Translation) and therefore may also  work  with  hdparm. To see how your hard disk does compare: # hdparm -t...

SARG – Squid Analysis Report Generator Configuration is a tool that allow you to view “where” your users are going to on the Internet. SARG provides many information about Squid users activities like, times, bytes, sites, etc… Download latest version of SARG from here. # wget http://...

PowerDNS is a DNS server, written in C++ and licensed under the GPL. It runs on most Unix derivatives and on Microsoft Windows. PowerDNS can be managed through a web interface (PowerAdmin). Install MySQL, # yum install mysql* -y After installation, start it and create system startup links for MySQL. # service mysqld start; chkconfig mysqld on If you want to set root password, # mysqladmin -u root...

eAccelerator is a free open-source PHP accelerator, optimizer, and dynamic content cache. It increases the performance of PHP scripts by caching them in their compiled state, so that the overhead of compiling is almost completely eliminated. It also optimizes scripts to speed up their execution. eAccelerator typically reduces server load and increases the speed of your PHP code by 1-10 times. I have tested this...

Linux kernel has PC speaker bell driver called pcspkr.ko. It is responsible for generating beeps while users are working on Shell Prompts ( Both Virtual and GUI Terminals ). If you don't like it, simply remove driver from kernel. Login as a root and type the following command to unload the driver: # rmmod -v pcspkr Sample output: rmmod pcspkr, wait=no We...

“ViCompress HTTP proxy server reduces download time by gzip compressing text pages before sending them on the client. This results in faster download times, especially over slow network connections. ViCompress works with existing web servers and web browsers. All modern browsers (Internet Explorer, Firefox, Safari, Chrome) recognize gzip-encoded data, and will automatically decompress the data on the f...

Every time I connect to Linux server, I receive the same message and I’m getting tired of seeing it, so I decided to change the message to something else. Here’s the message that I get every time: [root@server1 ~]# ssh linuxarticles.org root@linuxarticles.org's password: Last login: Mon Oct 11 18:58:43 2010 from loc...

After downloading ISO file from Fedora/CentOS, you can check the integrity of the ISO-file with a checksum, the md5sum. The mirror will offer you a separate text file to download with a 128 bit string of characters. This string has to be exactly the same as the one you get when you do: # md5sum file.iso 0c0f8ff9b6fb60a4778288de0d9e7f46  file.iso We assume that, you have downloaded ...

Dropbox is a Web-based file hosting service operated by Dropbox, Inc. which uses cloud computing to enable users to store and share files and folders with others across the Internet using file synchronization. It was founded in 2007 by MIT graduates Drew Houston and Arash Ferdowsi as a Y Combinator startup says Wikipedia.   To install DropBox on your system, download appropriate rpm for your...

Fileop utility does file operation on the filesystem and gives the ops/sec for each operation. This tool will be useful to test your filesystem performance as well as storage performance. Or, if you are going to select a filesystem or storage that is going to host huge number of small files (like source codes), then fileop can be used for benchmarking. First Install  ...