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SOSREPORT in Redhat Linux

LynuxStuff.com — Mon, 17 Dec 2012 07:25:22 +0000

The sosreport is a tool that collects the configuration and diagnostic information from Redhat Enterprise Linux Machine. The sosreport will collect information like the running kernel version, loaded modules,system configuration files and other system related information to archive file.

RHEL 6 file permission with dot – File mode bit

LynuxStuff.com — Wed, 28 Nov 2012 07:37:40 +0000

The file mode bits is a single character that specifies whether an alternate access method such as an access control list applies to the file.

How to disable selinux

LynuxStuff.com — Fri, 23 Dec 2011 16:48:27 +0000

In this article we are going to check how to disable SELinux in Centos Box.SELinux brings lot of security measures to your Linux box.It will provide an additional level of access control mechanism to files and folders on top of normal Linux security tools.

Setting Up a Local yum Server

LynuxStuff.com — Fri, 02 Dec 2011 18:20:05 +0000

Sometimes you feel it is necessary or to be handy to have a local yum server in your network.So let's try to create a local yum server in your network.

Using yum with a proxy server

LynuxStuff.com — Tue, 22 Nov 2011 16:23:52 +0000

This how to article for using yum with a proxy server describe how to configure YUM to work behind proxy server using username and password.If you are behind proxy server then you need to configure yum to pass proxy server.

Server Configuration checking commands

LynuxStuff.com — Sat, 19 Nov 2011 15:29:47 +0000

Linux server configuration file checking commands in brief.These commands are useful for verifying configuration files in Linux server before applying to the server.

7 important uses of LSOF Command for Linux admin

LynuxStuff.com — Thu, 10 Nov 2011 20:48:09 +0000

important uses of LSOF Command - lsof is a Linux utility which lists the information about files opened by processes.LSOF is one of the powerful tool available for troubleshooting problems.

Configure NAT in Linux box using IPTABLES

LynuxStuff.com — Sun, 23 Oct 2011 14:29:19 +0000

NAT-Network Address Translation is used to communicate from one network to other network with different sub-net.So your Linux box will act as a gateway and will allow to communicate between two different networks.

Convert Linux man pages to PDF

LynuxStuff.com — Fri, 02 Sep 2011 19:06:51 +0000

Here we are trying to find out how to convert Linux man pages to PDF. Man Pages are most reliable reference available for Linux users and man command remains the easiest way to access those reference pages.

Manage password aging in Linux systems

LynuxStuff.com — Fri, 26 Aug 2011 23:38:11 +0000

password expiry for users is configuring in /etc/login.defs file.These are the password aging parameters PASS_MAX_DAYS Maximum number of days a password may be used. PASS_MIN_DAYS Minimum number of days allowed between password changes. PASS_WARN_AGE Number of days warning given before a password expires. By default PASS_MAX_DAYS will be 99999 days that means no password expiry.So we are going to configure password expiry for all users in 90 days and minimum days between password change is 1 day. Open /etc/login.defs and [...]

Autoconf – brief introduction for beginners

LynuxStuff.com — Thu, 25 Aug 2011 23:59:03 +0000

Autoconf is a set of tools which makes your project configurable and portable for running in Linux distributions. Simply, autoconf will help you to create configure script and Makefile for your code. Before going to generate configure script using autoconf, we need to define set of rules and dependencies. We are defining that rules and dependencies in two files, configure.in and Makefile.in. Create default Makefile and keep in project directory.We can genarate the configure.in based on the rules specified in [...]

EXIM Mail Server on CENTOS

LynuxStuff.com — Wed, 24 Aug 2011 22:49:03 +0000

Steps: #yum install exim system-switch-mail After successful installation, we need to make some necessary configurations. Switch default MTA(Mail Transfer agent) to exim if it is sendmail or any other application by using system-switch-mail. Then stop sendmail service if it is running and disable in startup. #service sendmail stop #chkconfig sendmail off And start exim service and enable to start at boot time #service exim start #chkconfig exim on If you want to enable manual routing for mail then ,add the [...]

How to disable ping requests in Linux box

LynuxStuff.com — Sun, 07 Aug 2011 17:27:53 +0000

The basic network discovery always start with ping utility.So blocking the ping requests will make the system discovery difficult.To disable ping requests ,we just need to add/modify some kernel parameters. What we are doing here is the permanent change. So open /etc/sysctl.conf and add the following line to /etc/sysctl.conf net.ipv4.icmp_echo_ignore_all = 1 And reload kernel parameters using command sysctl -p (sysctl -p is used to reload kernel parameters at runtime). After successful configuration,if any one try to ping your server [...]

Centralized log host using Syslog

LynuxStuff.com — Sat, 06 Aug 2011 07:45:15 +0000

Building a centralized log host in your network will ease the process of troubleshooting your servers from a single window.Centralized log host will accepts all the log messages from client and store in that server.

10 basic commands a system admin need to know

LynuxStuff.com — Fri, 29 Jul 2011 21:12:42 +0000

tty – tty command will tells you current terminal. #tty /dev/pts/1 whoami- whoami commands tells you current logged-in username #whoami root which- which command will give you the path of the command #which tty /usr/bin/tty set- set command prints and sets the shell variables or environment variables echo-echo command will prints the output to screen #echo $PWD print current working directory to the screen. history-history command will tells you the command history clear or ctrl+l- This will clear the terminal [...]

Environment Variables in Unix

LynuxStuff.com — Tue, 12 Jul 2011 19:28:04 +0000

Environment variables in Unix are a set of dynamic named values that can affect the way running processes will be have on a computer

How to record a UNIX terminal session

LynuxStuff.com — Sat, 09 Jul 2011 17:24:06 +0000

script is one of the powerful tool available to record a unix terminal session.Start the recording of Unix terminal session with script command.And start doing your important configurations, it will recorded in a file. After completing the task ,you can exit the recording with exit command Example procedure: [root@core-22 ~]# script Script started, file is typescript [root@core-22 ~]# service httpd stop Stopping httpd: [ OK ] [root@core-22 ~]# service httpd start Starting httpd: [ OK ] [root@core-22 ~]# exit exit [...]

How to find current system runlevel

LynuxStuff.com — Sat, 09 Jul 2011 07:19:42 +0000

What is run level in Unix??? Run level defines the predefined set of operational state for Unix system.The operational state is defined in file inittab which is located in /etc. init command used to switch between different run levels.init command followed by runlevel will switch system to corresponding runlevel Eg: init 3 This will switch system to run level 3 which is text mode. Standard Linux distributions have the following run levels: No Name Description 0 Halt System will go [...]

Boot Linux GRUB into single user mode

LynuxStuff.com — Fri, 08 Jul 2011 18:21:05 +0000

First runlevel for Linux system which only one user is allowed to access that root user.Single user mode is useful for fixing some system problem like filesystem errors,recovering root password etc.So these are the steps for entering to single user mode in Linux.This is based on redhat enterprise linux 5( RHEL 5) Steps: Press any key during booting to go to OS listing Hit ‘e‘ to edit the selected command in the boot sequence(Read the specified instructions in bottom of [...]

PAM-Plugable Authentication Modules

LynuxStuff.com — Fri, 01 Jul 2011 09:54:59 +0000

PAM is an authentication layer that allows programs to be written independent of specific authentication scheme.The application request authentication via the PAM library and PAM library determines whether the user is allowed to proceed.If an administrator wants to implement a different authentication,he just change the PAM configuration files and existing program work seamlessly. All application and services that depend on PAM for authentication have a file in /etc/pam.d/ directory with filename being exactly the same as the application or service.The [...]