Linux Tips for Beginners

Introduction to Linux Series

This is my collection of Linux tips beginners, which I am adding to as I learn more about using Linux. This page serves as my notepad and reminders for commands and is published online in the hopes it helps others starting out with Linux.

Creating a Symbolic Link

A symbolic link is a pointer to another file or directory, like a shortcut in Windows. Unlike shortcuts however, the symbolic link can be used just like the original file or directory. Symbolic links are very good if you need to have multiple copies of the same file in different locations.

You can use the command below to create a symbolic link to a file.

ln -s {/path/to/file-name} {link-name}

Example below will create a link to /home/timtrott/public_html and create a "false" folder called /www. When you change directory to /www, you will really be in /home/timtrott/public_html.

ln -s /home/timtrott/public_html/www /www

Creating Shell Scripts

A shell script is a Linux version of a MS-DOS batch file, only a bit more flexible and powerful. They can be created using any text editor. I'm going to create a sample shell script that will mount a network drive.

All shell scripts start with #!/bin/bash. The following lines are executed line by line.

#!/bin/bash
sudo mount -t cifs //192.168.0.10/websites/www /usr/www

The script must have it's permissions changed to allow execute.

chmod +x scriptname

I like to keep my scripts in my home folder /home/tim/ That way I can call them using ~/scriptname.

Creating Multiple IP Addresses

I will be working on multiple websites at a time and as such I need to allocate an IP address to each one. I can do this by using IP alias. This is done easily enough by adding some entries to /etc/network/interfaces.

sudo pico /etc/network/interfaces

And add the following block of code. Repeat as required.

auto eth0:0
iface eth0:0 inet static
name Ethernet alias LAN card
address 192.168.0.101
netmask 255.255.255.0
broadcast 192.168.0.255
network 192.168.0.0

Once complete you need to restart the network interfaces.

sudo /etc/init.d/networking restart

Host Tables

A host table is a simple text file that associates IP addresses with host names, one line per IP address. It isn't normally necessary to change this, however I have a situation in which I need to redirect a host name for my database server to my local host.

sudo pico /etc/hosts

The format for the file is ip_address hostname alias. My hosts file looks like this:

127.0.0.1       localhost
192.168.0.5     mydomain.com   ubuntu
127.0.0.1       my.databaseserver1.com
127.0.0.1       my.databaseserver2.com

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Modifications to this file normally take effect immediately, except in cases where the file is cached by applications.

Enable the Power Button

By default on my installations, the power button does not function, except to immediately power off. Instead I'd rather send a power down message to the OS so that my server can gracefully close and power off.

First we need to install the Advanced Configuration and Power Interface (ACPI) package

sudo apt-get install acpid

And edit the config file if required

sudo pico /etc/acpi/powerbtn.sh

When the power button is pressed, the system no goes down with a message stating the power button has been pressed.

/sbin/shutdown -h now "Power button pressed"

Linux Cheat Sheets

Here are a few very handy Cheat sheets for Linux which will introduce you to the basic commands.

Above all, the best way to learn Linux is to use it. Use it a lot.

Whenever you run into a problem with a command, do some online searching. Almost any time you run into a wall, you're going to find that a lot of people have run into it before you and a number of them will have written something about how they got over it.

Tutorial Series

This post is part of the series Introduction to Linux. Use the links below to advance to the next tutorial in the couse, or go back and see the previous in the tutorial series.