Linux Server

How to move the atom editor installable file to a different location?

When Atom editor is installed, it creates a symbolic link in /usr/local/bin folder. Get the new folder path where atom editor installable file resides and run the following command in the terminal

$ ln -s /NewFolder/Atom.app/Contents/Resources/app/atom.sh /usr/local/bin/atom

If a link is already created for the atom editor, then you need to remove the existing symbolic link before creating a new one

$ unlink AtomSymbolicLink (OR)

$ rm AtomSymbolicLink

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How to open a file in Atom editor from a Mac terminal?

When atom installs, it sets up a symbolic link to the location where it is installed. You can open a file or folder in atom by using the following commands

a) Open the editor

$ atom

b) Open a file

$ atom index.html

c) Open atom in the current folder

$ atom .

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Apache webserver (httpd) service installation on CentOS 7 Linux

First set up the httpd (web) service

$ yum install httpd

If httpd service is already installed, update the service

$ yum update httpd

Now, start the web server

$ service httpd start

Redirecting to /bin/systemctl start httpd.service

Check the status of the web server

$ service httpd status

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Setup Virtualbox Additions on Centos 7 to share files

First step is to install dependencies

$ sudo yum groupinstall “Development Tools”

$ sudo yum install kernel-devel

Mount the Virtualbox Additions CD ISO. You should download the virtualbox additions iso from http://download.virtualbox.org/virtualbox/ depending on your version of Virtual Box.

$ sudo mkdir /media/cdrom/

$ sudo mount /dev/cdrom /media/cdrom/

$ cd /media/cdrom

$ sudo ./VBoxLinuxAdditions.run

Before this step, create a shared folder in your host system. Say for example, if you created a shared folder named “CentosShare” in the host system you will follow the steps given below to access the share from within Centos.

$ mkdir ~/share

$ mount -t vboxs CentosShare ~/share

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PHP SYSTEM WARNING: ‘date(): It is not safe to rely on the system’s timezone settings

Edit /etc/php.ini and add the timezone setting within the file. For a list of timezone settings, visit http://php.net/manual/en/timezones.php


[Date] ; Defines the default timezone used by the date functions
; http://php.net/date.timezone
date.timezone = America/New_York

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How to avoid search engines from crawling your website?

Your answer is to create a robots.txt file in the root of your web directory and to have the code setting given below in the file.

User-agent: *
Disallow: /

You can read more about Robots exclusion protocol, here

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Linux: How the password is stored, salted and hashed securely?

In earlier systems, passwords were stored in the file /etc/passwd and they were not encrypted.

After the user is created, an entry gets recorded in /etc/passwd with ‘x’ in the second column instead of the acutal password.

$ useradd timmy

$ cat /etc/passwd
timmy:x:1002:1003::/home/timmy:/bin/sh

For security reasons, passwords are now stored in the file /etc/shadow and they are encrypted. Password was not set initially, when the user was created. This is indicated by !! mark (in RedHat, ! – Debian)

$ cat /etc/shadow

timmy:!!:15870:0:99999:7:::

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How to remove ^M characters at the end of lines in Vi from files in Linux?

Files created in windows when moved to linux will have ^M character at the end of lines when you open the files in Vi editor.

To remove the strange characters open the file in Vi editor and type

:%s/.$// 

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How to determine the file system type in Linux?

Linux supports many file system types like Ext2, Ext3, Ext4, NFS, FAT16, FAT32, NTFS etc. To find out what type of file systems are mounted in your system, issue the command

$ df -T

Output from the command

Filesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sda1     ext4    94088076   9090252  80218356  11% /
udev      devtmpfs     1023536         4   1023532   1% /dev
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How to install and setup Fail2ban on CentOS?

Fail2ban is a software used to ban IP’s which shows strange behavior. It can be configured to reject IP’s for a certain amount of time.

To install Fail2ban we need to download the application from the source. Login as the root user and go to /opt

$ cd /opt

$ wget http://downloads.sourceforge.net/project/fail2ban/fail2ban-stable/fail2ban-0.8.4/fail2ban-0.8.4.tar.bz2?use_mirror=transact

Next unzip the downloaded file

$ tar -xf fail2ban-0.8.4.tar.bz2

$ cd fail2ban-0.8.4
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