By default, MySQL only allows connections from the localhost address – 127.0.0.1. The configuration file is usually found in /etc/my.cnf. To switch MySQL to listen on TCP, Open /etc/my.cnf or /etc/mysql/my.cnf. # vim /etc/my.cnf Modify line as below # bind-address  = 127.0.0.1 Save and Exit the file. Now restart the database server by executing, # /e...

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: ...

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...

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,...

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 ...

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, #...

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...

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...

The default configuration for firewall is to reject all incoming packets from outside. To allow it, we need to open particular port in Firewall. The default configuration file for iptables based firewall under RHEL / CentOS / Fedora Linux is /etc/sysconfig/iptables. Open /etc/sysconfig/iptables, # vim /etc/sysconfig/iptables Append rule as follows: -A RH-Firewall-1-INPUT -m state...

There are various methods to run multiple instances of mysql (on different ports) on the same machine. Here I have used the same binary and used a separate configuration file (with separate port, pid, socket and data directory). We need to create new directories for our datadir and log folder (if used). Also we need to assign proper permissions on those folders: # mkdir /var/lib/mysql2 # chown -R mysql.mysql...

YUM is an interactive, rpm based, package manager. It can automatically perform system updates, including dependency analysis and obsolete processing based on "repository" metadata. It can also perform installation of new packages, removal of old packages and perform queries on the installed and/or available packages among many other commands/services (see below). yum is similar to other high level package ...

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...

Backing up MySQL database is a very important system administration task, and should generally be run automatically from cron. We will use the mysqldump utility included with mysql to dump the contents of the database to a text file that can be easily restore. # mysqldump -h localhost -u root -p root_password DataBase > DB_name_Bkp.sql This will generate a text file containing ...

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 ...

“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...

We can configure apache – httpd service to listen Multiple ports via Listen directive. By default httpd listens on TCP port 80. To configure multiple ports, open file /etc/httpd/conf/httpd.conf and modify the Listen directive tells the server to accept incoming requests on the specified port # vi /etc/httpd/conf/httpd.conf Find, Listen 80 Force apache to listen to port 8...

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...

If you run a dual-boot system with Linux and Windows, and reinstalling Windows XP after OS corrupt.  Windows XP will wipes over write grub entry or writing MBR sector. To recover GRUB, STEP 1: Boot off the Live CD enter into rescue mode, STEP 2: Open a Terminal and type in the following commands, noting that the first command will put you into the grub “prompt”, and ...

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 ...

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  ...

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...

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...

If you are using Linux Desktop Operating System and do not want to set up an email server, use GMail account to relay emails. On Desktop OS, we can use GUI Email Clients, which supports POP3/IMAP to send an email but how about /usr/bin/mail or from cmd prompt? To fulfil your requirement, you need to install a simple program called ssmtp. It accepts a mail stream on standard input...

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...

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 re-set root password, first stop mysql service. # service mysqld stop # mysqld_safe...