Linux

Delete all but not last n lines

Leave last few lines and delete all

How do I delete a huge file except last n lines of a file? vi editor has a feature called "ex", By using it you can delete all lines of a file except n lines from a file Create a file with n lines # for i in $(seq 1 2500); do  ..

How to flush linux DNS cache nscd

Using nscd command to flush dns cache

The nscd caches are saved to disk on RedHat system, they are located in /var/db/nscd # ls /var/db/nscd/ group hosts netgroup passwd services When you stop or restart nscd these files just stay there and restarting really wont clear or flush your  ..

How to calculate total diskspace in terminal

Covert Kilobytes to Megabytes or gigabytes of disk

To find the disk size # fdisk -s /dev/sdb 62914560 In the above command the disk space will be printed in KB. But I had the requirement to print the values in MB or GB for multiple servers. To print diskspace in Megabytes or MB # echo  ..

How to calculate total memory in terminal

Covert Kilobytes to Megabytes or gigabytes through terminal

When I tried to run size of my memory, I executed below command and found the result in KB # grep 'MemTotal' /proc/meminfo I can also run free -m or free -g to read the output in MB or GB. But when I have list of values in  ..

Adding rhq agent during system boot

Running rhq agent as a Daemon or init.d Service

Normally the agent should be started as a background daemon process. On Windows, this runs as a service. On Linux and Unix systems, the agent starts at boot time from init.d Register rhq-agent-wrapper.sh with chkconfig. # /sbin/chkconfig --add rhq-agent-wrapper.sh Enable the agent service to run at boot time and have it  ..

Chown for symbolic link

Change ownership for symbolic link

The chown command changes the user ID and/or the group ID of the specified files. Symbolic links named by arguments are silently left unchanged unless -h is used. Changing the owner of a symbolic link needs special attention. When you use chown the regular way to change the owner of a  ..

How to install and configure ansible on fedora

Installing Ansible Playbook

Great things about Ansible is that you dont need to install an Ansible client on the servers you are managing. You only need to install Ansible on your local machine or on a master server that can connect to the managed servers via SSH. Ansible works by configuring client machines  ..

Reinstall format disk using dd command

Format disk using dd command

When you want to clean the disk or format the disk dd command will be very handy to use it. Format disk using dd command # dd if=/dev/zero of=/dev/sdb # dd if=/dev/null of=/dev/sdd bs=4096 count=1 This command will clean or wipe the data of your existing disk. Use this command  ..

How to mount nfts partiton on linux

Mount partition with ntfs file system and read write access

Today when I want to mount my external harddisk I felt uneasy since my Redhat linux does not support nfts partiton. NTFS3G is an open source cross-platform, stable, GPL licensed, POSIX, NTFS R/W driver used in Linux. It provides safe handling of Windows NTFS file systems. To proceed with mounting  ..

Yum download package without installing

Yum only download not to install

How to yum download a package without installing? Install downloadonly plugin for download option # yum install yum-utils # yum install yum-plugin-downloadonly How to yum download a package? # yum install --downloadonly --downloaddir=<directory> <package> Example: # yum install --downloadonly --downloaddir=./ kmod-VirtualBox-3.19.5-200.fc21.x86_64.x86_64 To download already installed packages # yumdownloader <package>   ..

How to find block size of filesystem

How to find block size of partition

How do I find block size of an partition on Linux? # tune2fs -l /dev/sda1 | grep -i 'block size' Block size: 1024 How do I find block size of a filesystem on Linux? #  ..

Yum install google chrome in fedora 21 22 cent os

How to install google chrome in fedora 21 22

As we all know google chrome is now becoming one of the most used browser, Its easy and simple to install in linux by following the below steps. To install Google Chrome in Fedora 20 / 19 / 18 / 17 / 16 / 15 / 14 and RHEL using  ..

How to run vlc player in root

Error VLC is not supposed to be run as root

Today I installed VLC as root and when I tried to execute or run vlc player I received error VLC is not supposed to be run as root. Installing VLC: To install VLC, your rpmfusion repo must be configured RPMfusion Free Release # yum localinstall --nogpgcheck http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-$(rpm -E %fedora).noarch.rpm RPMfusion NonFree Release   ..

How to list available shells in linux

Find shells present in server

chsh -l will list all the available shells in the # chsh -l /bin/sh /bin/bash /sbin/nologin /bin/tcsh /bin/csh /bin/zsh chsl --list-shell will also print he same result as chsh -l # chsh --list-shell /bin/sh   ..

Difference between sticky bit suid sgid

What is sticky bit, SUID, SGID

what is "sticky bit", "SUID" , "SGID"? 1) Sticky bit was used on executable in Linux (which was used more often)so that they would remain in the memory more time after the initial execution, hoping they would be needed in the near future. But since today we have more sophisticated memory  ..

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