• Multi Router Traffic Grapher – MRTG on Linux

    The Multi Router Traffic Grapher (MRTG) is a network or resource monitoring tool used by System Administrators across the Globe. MRTG generates HTML pages containing PNG images, which provides a real time visual representation of network traffic and system resources. STEP 1: Install MRTG with required packages # yum install mrtg net-snmp net-snmp-utils -y STEP 2:...
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  • Mount ISO Image Under Linux

    An ISO image is an disk image of an optical disc using a conventional ISO format. ISO image files typically have a file extension of .ISO. The name "ISO" is taken from the ISO 9660 file system used with CD-ROM media, but an ISO image can also contain UDF file system because UDF is backward-compatible to ISO 9660. You can mount an ISO images via the loop device under Linux. To mount ISO...
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  • Performance Monitoring Using “vmstat” on Linux

    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...
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  • Linux Swap Space Configuration ( Using File )

    Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM. Swap space is located on hard drives, which have a slower access time than physical...
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  • Ubuntu – Change Network Card MAC Address

    MAC stands for Media Access Control and in a sense the MAC address is a computer's true name on a LAN. An Ethernet MAC address is a six byte number, usually expressed as a twelve digit hexadecimal number. To change this setting, we’ll need to edit the /etc/network/interfaces file. You can choose to use a different editor if you’d like. $ sudo gedit /etc/network/interfaces You s...
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  • Test Memory Using memtester in Linux

    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...
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  • Access Windows NTFS Partitions From Linux

    Reading or accessing NTFS partitions in Linux is important for many reasons. NTFS-3G is an open source cross-platform implementation of the Microsoft Windows NTFS file system with read-write support. NTFS-3G often uses the FUSE file system interface, so it can run unmodified on many different operating systems.  Before we start, make sure that you have rpmforge repository configured. If you do not have,...
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  • SQUID - Timezone Modifications

    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...
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  • Restricting users from using the same old password in Linux

    For Authentication, Account Management and Authorization, PAM is the core module and pam_unix provides mentioned functionality. Same module can be used to maintain a list of old passwords for every user. This is useful if you want to disallow use of old passwords. You can find out old password list from /etc/security/opasswd file. Open /etc/pam.d/system-auth file of Fedora Core or Red Hat or...
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  • Enable Root Authentication in Linux Single User Mode

    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...
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  • Linux - Track NFS Disk I/O Stats

    The iostat command, Report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network file systems (NFS). The iostat command generates reports that can be used to change system configuration to better balance the input/output load between physical disks. The -n option displays the NFS disk statistics. Data displayed are valid only with kernels...
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  • Ctrl Alt Delete Deactivation in CentOS / RedHat / Fedora

    Anyone who has physical access to the keyboard can simply use the Ctrl Alt Delete key combination to reboot the server without passing any authentication credentials to server. To disable Ctrl Alt Delete, update /etc/inittab and make sure following line is commented out: # vim /etc/inittab # ca::ctrlaltdel:/sbin/shutdown -t3 -r now Save and exit...
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  • Nginx Installation and Configuration

    Nginx quickly delivers static content with efficient use of system resources. It can deploy dynamic HTTP content on a network using FastCGI handlers for scripts, and can serve as a very capable software load balancer. Nginx uses an asynchronous event-driven approach to handling requests which provides more predictable performance under load, in contrast to the Apache HTTP server model that uses a threaded or...
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  • Kernel Panic Reboot in Linux

    By default after a kernel panic, Linux kernel just waits there for a system administrator to hit the Ctrl+Alt+Del to restart or power cycle button. This is because of the value set on "kernel.panic" parameter to Linux Kernel. # cat /proc/sys/kernel/panic 0 or # sysctl -a | grep kernel.panic kernel.panic = 0 To disable this and make the Linux OS...
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  • Set up Google Public DNS on Linux

    Google has recently released their very own DNS resolver with main goals of making web browsing faster and safer. Since Google's search engine already crawls the web on a daily basis and in the process resolves and caches DNS information, they wanted to make use of their technology to experiment with new ways of addressing some of the existing DNS challenges around performance and security. For advanced...
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  • Difference between su and root

    As you login as “root” right from booting the system, all the privileges are set to root, what makes your system more vulnerable to your own mistakes and those wishing to enter your system. As you login as normal user, the privileges are limited, thus it´s safer. To be able to do administrative tasks you can temporally login as root using “su” in a console/terminal, that way the root privileges ...
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  • How to Create RPM?

     In RedHat/CentOS/Fedora, software are packaged in .rpm format. rpm is a powerful Package Manager, which can be used to build, install, query, verify, update, and erase individual software packages. A package consists of an archive of files and meta-data used to install and erase the archive files. The meta-data includes helper scripts, file attributes, and descriptive information about the package. Packages...
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  • Linux - Turn off Beep Sound of Terminal

    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...
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  • Backup MySQL Table Structure To a File

    The mysqldump client is a backup program originally written by Igor Romanenko. It can be used to dump a database or a collection of databases for backup or transfer to another SQL server (not necessarily a MySQL server). The dump typically contains SQL statements to create the table, populate it, or both. However, mysqldump can also be used to generate files in CSV, other delimited text, or XML...
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  • Linux Filesystem IO benchmarking tool - Fileop

    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  ...
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  • Bz2 tar file contents listing

    bzip2 compresses  files  using  the Burrows-Wheeler block sorting text compression algorithm, and Huffman coding.   Compression  is  generally considerably   better   than   that   achieved   by  more  conventional LZ77/LZ78-based compressors, and approaches the performance of the  PPM family of statistical compressors. To list the contents of a tar.bz2 file, use tar command as follows: ...
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  • Apache Linux - Limiting User Upload File Size

    To restricts Users from uploading File Size, we can configure Apache with LimitRequestBody Directive. You can add this directive using .htaccess file or httpd.conf file under virtual host or directory configuration options. You can set value (in bytes) from 0 (unlimited) to 2147483647 (2GB) that are allowed in a request body. For example, limit /var/www/html/linuxarticles.org/uploads to 200K,...
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  • RSYNC

    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...
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  • Release memory in Linux (Unused or Cached)

    In computer science, Memory Leakage occurs when a computer software or program consumes required memory but unable to memory after completing its task or when no longer needed to Operating System. There are two types of Memory Leakage. One is Virtual Memory Leakage and another is Real Memory Leakage. Now first Identify cached memory or unused memory by executing, ...
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  • Set MySQL Root Password

    For mysql, the system administrator user is called root. We will use the mysqladmin utility from a command line to set the new password. Default password is not secured at all. By default in RedHat, Fedora and Centos default password is null. So it is always better to set root password. To set root password, # mysqladmin -u root password XyZ@aBc@123 # mysqladmin -u root -h ...
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Disable ipv6 in Ubuntu

Jun 16th

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Internet Protocol Version 6 (IPv6) is a network layer protocol that enables data communications over a packet switched network. Packet switching involves the sending and receiving of data in packets between two nodes in a network.

Ubuntu Linux – Flush DNS cache

Jun 15th

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Sometimes you may get old web results and old webpages even after updating the web pages. That means, DNS cache holds the problem. To solve this problem, execute below command to flush DNS cache.  # /etc/rc.d/init.d/nscd restart

Hardware – SMPS Power Supply Calculator

Jun 14th

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A switched-mode power supply (switching-mode power supply, SMPS, or simply switcher) is an electronic power supply that incorporates a switching regulator in order to be highly efficient in the conversion of electrical power.

Open RAR File In Linux

Jun 13th

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RAR stands for Roshal ARchive. It is a non-documented archive file format that supports data compression, error recovery, and file spanning. It was developed by a Russian software engineer, Eugene Roshal (the first letter of his surname contributing to the name of the archive format), and is currently licensed by win.rar GmbH.

Restart ADSL Router Using Shell Script

Jun 11th

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For Internet users, who are using MTNL ADSL routers, they need to restart router after some. To do the same, we need to login to the router via telnet and have to run reboot command or have to manually unplug the power cable. To make the task simple, we can use this simple script which will reboot the router by just running the script.

ISO File Modification Using ISO Master

Jun 11th

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ISO Master is an open-source, easy to use, graphical CD image editor for Linux and BSD. Basically you can use this program to extract files from an ISO, add files to an ISO, and create bootable ISOs – all in a graphical user interface. ISO Master can open ISO, NRG, and some MDF files but…

MySQL – Basic Commands To Know

Jun 10th

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MySQL is a simple SQL shell (with GNU read line capabilities). It supports interactive and non interactive use. When used interactively, query results are presented in an ASCII-table format. When used non interactively (for example, as a filter), the result is presented in tab-separated format. The output format can be changed using command options.

After Installation of MySQL on Linux System, start it by,

Fail2ban on Ubuntu Linux to Stop Brute Force Attacks

Jun 10th

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Fail2Ban scans log files like /var/log/pwdfail and bans IP that makes too many password failures. It updates firewall rules to reject the IP address. These rules can be defined by the user. Fail2Ban can read multiple log files such as sshd or Apache web server ones. Many times system administrator have to face brute force…

Extract A File From RPM

Jun 9th

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RPM is a powerful Package Manager, which can be used to build, install, query, verify, update, and erase individual software packages. A package consists of an archive of files and meta-data used to install and erase the archive files. The meta-data includes helper scripts, file attributes, and descriptive information about the package.

VSFTPD – Creating Virtual Users on Linux

Jun 9th

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Virtual Users means, there is no need to create system users or physical user accounts, users can be maintained using htpasswd. Using virtual users, they can get access to same ftp files via Apache. Download and Install pam-pam_pwdfile from here. # wget ftp://ftp.pbone.net/mirror/ftp.pld-linux.org/dists/2.0/PLD/i386/PLD/RPMS/pam-pam_pwdfile-0.99-2.i386.rpm # rpm -ivh pam-pam_pwdfile-0.99-2.i386.rpm Now, append following lines to /etc/pam.d/vsftpd.pwd. # vim…

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