Category Archives: shell scripting

Step by Step Procedure To Setup Cassandra Cluster On Any Linux Distribution

Step by Step procedure to set-up Cassandra Cluster On Any Linux Distribution

1. What is Cassandra : Cassandra is an open source distributed database management system designed to handle large amounts of data across many commodity servers, providing high availability with no single point of failure.

2. Cassandra Cluster: A cluster is arranged as a ring of nodes. Clients send read/write requests to any node in the ring; that node takes on the role of coordinator node, and forwards the request to the node responsible for servicing it. A partitioner decides which nodes store which rows. The recommended partitioners assign rows to nodes based on a hash value of the row key. Nodes are assigned tokens that evenly divide the full range of possible hash values.

3. Prerequisites :
Setup iptables, allow below Cassandra ports.
For Centos:
iptables -A INPUT -p tcp -m tcp –dport 9160 -j ACCEPT
iptables -A INPUT -p tcp -m tcp –dport 7000 -j ACCEPT
iptables -A INPUT -p tcp -m tcp –dport 7001 -j ACCEPT
service iptables restart

For Ubuntu:
iptables -A INPUT -p tcp -m tcp –dport 9160 -j ACCEPT
iptables -A INPUT -p tcp -m tcp –dport 7000 -j ACCEPT
iptables -A INPUT -p tcp -m tcp –dport 7001 -j ACCEPT
sudo sh -c “iptables-save > /etc/iptables.rules”
sudo iptables-apply /etc/iptables.rules
Applying new iptables rules from ‘/etc/iptables.rules’… done.
Can you establish NEW connections to the machine? (y/N) y
… then my job is done. See you next time.

4. Installing Cassandra and Configuring: Login to Remote machine, where you want to install Cassandra.
Below are the steps to install and configure Cassandra Cluster.

Get Cassandra tar-ball
wget “http://downloads.datastax.com/community/dsc-cassandra-2.1.7-bin.tar.gz” -P /usr/share/
Setup Cassandra environment under /usr/share
tar -xvzf /usr/share/dsc-cassandra-2.1.7-bin.tar.gz -C /usr/share/

Delete tar file
rm -rf /usr/share/dsc-cassandra-2.1.7-bin.tar.gz

Cassendra configuration change cluster_name : change clustername with your Cluster
sed -i ‘s/Test Cluster/{{clustername}}/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change listen_address : hostname=serverip
sed -i ‘s/listen_address\:\ localhost/listen_address\:\ {{hostname}}/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change rpc_address
sed -i ‘s/rpc_address\:\ localhost/rpc_address\:\ 0.0.0.0/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change endpoint_snitch
sed -i ‘s/endpoint_snitch\:\ SimpleSnitch/endpoint_snitch\:\ GossipingPropertyFileSnitch/g’ /usr/share/dsc-
cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change broadcast_rpc_address hostname=serverip
sed -i ‘s/^# broadcast_rpc_address\:\ 1.2.3.4/broadcast_rpc_address\:\ {{hostname}}/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change seeds hostname=serverip seeds=seedsip
sed -i ‘s/- seeds\:\ “127.0.0.1”/- seeds\:\ “{{seeds}},{{hostname}}”/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change data_file_directories
sed -i ‘s/# data_file_directories/data_file_directories/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change /var/lib/cassandra/data
sed -i” ‘107 s/^#//’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change commitlog_directory
sed -i ‘s/# commitlog_directory/commitlog_directory/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change saved_caches_directory
sed -i ‘s/# saved_caches_directory/saved_caches_directory/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change thrift_framed_transport_size_in_mb
sed -i ‘s/thrift_framed_transport_size_in_mb\:\ 15/thrift_framed_transport_size_in_mb\:\ 100/g’ /usr/share/dsc-
cassandra-2.1.7/conf/cassandra.yaml

Cassendra configuration change phi_convict_threshold
sed -i ‘s/# phi_convict_threshold\:\ 8/phi_convict_threshold\:\ 10/g’ /usr/share/dsc-cassandra-2.1.7/conf/cassandra.yaml

Start Cassandra service
nohup sh /usr/share/dsc-cassandra-2.1.7/bin/cassandra

5. Command to check Cassandra cluster:
/usr/share/dsc-cassandra-2.1.7/bin/nodetool status
Address Status State Load Owns Token
113427455640312821154458202477256070484
10.1.1.7 Up Normal 459.27 MB 33.33% 0
10.1.1.8 Up Normal 382.53 MB 33.33% 56713727820156410577229101238628035242
10.1.1.6 Up Normal 511.34 MB 33.33% 113427455640312821154458202477256070484

Step by Step procedure to install and Configure ANSIBLE on Ubuntu

Step by step procedure to install and configure ansible on ubuntu

Before installing ANSIBLE, let us understand,

What is ANSIBLE ?

1.Ansible Introduction :

Ansible is an IT automation tool. It can configure systems, deploy software, and orchestrate more advanced IT tasks such as continuous deployments or zero
downtime rolling updates.
Ansible’s goals are foremost those of simplicity and maximum ease of use. It also has a strong focus on security and reliability, featuring a minimum of moving parts, usage of OpenSSH for transport (with an accelerated socket mode and pull modes as alternatives),
and a language that is designed around auditability by humans – even those not familiar with the program.

While there are many popular configuration management systems available for Linux systems, such as Chef and Puppet, these are often more complex than many people want or need.Ansible is a great alternative to these options because it has a much smaller overhead to get started.

for more information visit, Ansible docs.
http://docs.ansible.com/

Assumptions
● You have a ubuntu 12.04 and you are logged-in as root.

2.How Does Ansible Work :
Ansible works by configuring client machines from an computer with Ansible components
installed and configured.
It communicates over normal SSH channels in order to retrieve information from remote
machines, issue commands, and copy files. Because of this, an Ansible system does not require any additional software to be installed on the client computers.
This is one way that Ansible simplifies the administration of servers.
Configuration files are mainly written in the YAML data  format due to its
expressive nature and its similarity to popular markup languages.Ansible can interact with clients through either command line tools or through its configuration scripts called Playbooks.

3. Install Ansible on an Ubuntu 12.04 :
To begin exploring Ansible , we need to install the Ansible package on at least one machine. I have used ubuntu 12.04

git clone git@github.com:ansible/ansible.git
cd ansible
source ./hacking/env-setup
sudo pip install paramiko PyYAML jinja2 --upgrade

We now have all of the software required to administer our servers through Ansible.
Set Up SSH Keys , Ansible primarily communicates with client computers through SSH.While it certainly has the ability to handle password-based SSH authentication, SSH keys help keep things simple.

4. Creating a SSH Pair :
@Server:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa):
Created directory ‘/home/a/.ssh’.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A
Now use ssh to create a directory ~/.ssh as user b on Client. (The directory may already exist,
which is fine):
@Server:~> ssh root@123.123.123.123 mkdir -p .ssh
root@Client’s password:
Finally append a’s new public key to root@123.123.123.123:.ssh/authorized_keys and enter
client’s password one last time:
root@Server:~> cat .ssh/id_rsa.pub | ssh root@123.123.123.123 ‘cat >> .ssh/authorized_keys’
root@Client’s password:
From now on you can log into Client as root from A as a without password:
@Server:~> ssh root@123.123.123.123

5. Configuring Ansible Host:
Ansible keeps record of all of the servers that it know through a “hosts” file. We need to configure this file first before we can begin to communicate with our other computers.
Open the file and add,

vim /etc/ansible/hosts
[hosts]
devops ansible_ssh_host=123.123.123.123

Where hosts is list of nodes
devops = host name of one of the client.
123.123.123.123 is hosts ip.
To do this, we will create a directory in the Ansible configuration structure called group_vars.
Within this folder, we can create YAML-formatted files for each group we want to configure:

sudo mkdir /etc/ansible/group_vars
sudo nano /etc/ansible/group_vars/hosts

We can put our configuration in here. YAML files start with “—“, so make sure you don’t forget that part.

ansible_ssh_user: root
Save and close this file when you are finished.

6. Ansible test Examples:

Using Simple Ansible Commands
Now that we have our hosts set up and enough configuration details to allow us to
successfully connect to our hosts, we can try out our very first command.
Ping all of the servers you configured by typing:
root@server:/etc/ansible# ansible -m ping hosts
devops | success >> {
“changed”: false,
“ping”: “pong”
}
This is a basic test to make sure that Ansible has a connection to all of its hosts.

ansible -m shell -a ‘ifconfig’ devops

devops | success | rc=0 >>
eth0 Link encap:Ethernet HWaddr 00:0c:29:a2:42:c4
inet addr:123.123.123.123 Bcast:10.27.111.255 Mask:255.255.255.0

ansible -m shell -a ‘free -m’ devops
devops | success | rc=0 >>
total used free shared buffers cached
Mem: 487 440 47 0 108 173
-/+ buffers/cache: 158 329
Swap: 507 66 441

Lets install sendmail on client from Ansible server, to do that create playbook.yml file in
/etc/ansible 100 Jul 5 02:48 playbook.yml

root@server:/etc/ansible# cat playbook.yml

– hosts: devops
tasks:
– name: 1. install sendmail
apt: name=sendmail state=present

Now execute below command to install on remote server.
ansible-playbook –inventory-file=hosts playbook.yml –sudo –verbose
Below is the result,

ansible 1

Before executing above command, sendmail was not installed. ansible 2

Later after execution, sendmail installed on the remote host.

Advantages of Automation,

,Automation-Advantages

Hence we have Installed and Configured ANSIBLE, Enjoy !!!

shell script to replace a string in a file

shell script to replace a string in a file

Some times during automating any task, we may require to replace a string in a file.
Example:- I want to change “Linux” string with “Waseem” in a file called string.txt

cat replacestring.sh
#!/bin/bash
# Shell Script to replace string in a file
/bin/sed -i “s/Linux/Waseem/g” /PATH/TO/FILE/string.txt
exit 0;

Before:-
—————–
cat string.txt
Linux

Run the script:-
——————-
sh replacestring.sh

After:-
——————
cat string.txt
Waseem

Another way we can replace string by passing parameter,so that the script will be used dynamically.
cat replacestring.sh
#!/bin/bash
# Shell Script to replace string in a file
/bin/sed -i “s/$1/$2/g” /PATH/TO/FILE/string.txt
exit 0;

Run the script:-
—————–
sh replacestring.sh Linux Waseem

Shell Script : Auto Enable/Disable Specific Cronjob

Shell Script : Auto Enable/Disable Specific Cronjob

What is Cronjob ?
A cron job is a scheduled task that is executed by the system at a specified time/date.

Sometimes we want to perform some task during specific time(Ex: During production Hours), and once the production time completes, we will be disabling cronjob. this requires manual work.The above manual work, can be automated with this script.

Create two scripts,
1.Auto_enable_cron.sh
2. Auto_disable_cron.sh

Below are both the scripts with cronjob details,

COMMANDS used:

crontab -l | sed ‘/^#.*GIVE-SCRIPT-NAME-HERE.sh/s/^#//’ | crontab –
crontab -l | sed ‘/^[^#].*GIVE-SCRIPT-NAME-HERE.sh/s/^/#/’ | crontab –

cronandscript

cronoutput

In the above image we can see that after running Auto_enable_cron.sh
The script in the cron GIVE-SCRIPT-NAME-HERE.sh is uncommented and after running
Auto-disable_cron.sh the script GIVE-SCRIPT-NAME-HERE.sh is commented again.

Now add scripts to desired time in cronjob.
9 * * * * /home/cronjob/Auto_enable_cron.sh (This will enable GIVE-SCRIPT-NAME-HERE.sh @9)
23 * * * * /home/cronjob/Auto_disable_cron.sh (This will disable GIVE-SCRIPT-NAME-HERE.sh @23)

Enjoy, just now you have automated your task!!!!.

Shell Script : Basic mathematics

#!/bin/bash
# SCRIPT: calc.sh
# PURPOSE: Addition, Subtraction, Division and Multiplication of
# two numbers.
#
#####################################################################
# Variable Declaration #
#####################################################################

clear #Clears Screen

Bold=”\033[1m” #Storing escape sequences in a variable.
Normal=”\033[0m”

echo “$Bold Basic mathematics using bash script $Normal\n”

items=”1. ADDITTION
2. SUBTRACTION
3. MULTIPLICATION
4. DIVISION
5. EXIT”

choice=

#####################################################################
# Functions Starts from here #
#####################################################################
exit_function()
{
clear
exit
}

#Function enter is used to go back to menu and clears screen

enter()
{
unset num1 num2
ans=
echo “”
echo -e “Do you want to continue(y/n):\c”
stty -icanon min 0 time 0
while [ -z “$ans” ]
do
read ans
done

#The while loop ensures that so long as at least one character is

if [ “$ans” = “y” -o “$ans” = “Y” ]
then
stty sane # Restoring terminal settings
clear
else
stty sane
exit_function
fi
}

#####################################################################
# CALC Script MENU #
#####################################################################

while true
do
echo “$Bold \tWelcome to Waseem’s Tutorial $Normal\n”
echo “\t$items \n”
echo -n “Enter your choice : ”
read choice

case $choice in
1) clear
echo “Enter two numbers for Addition : ”
echo -n “Number1: ”
read num1
echo -n “Number2: ”
read num2
echo “$num1 + $num2 = `expr $num1 + $num2`”
;;
2) clear
echo “Enter two numbers for Subtraction : ”
echo -n “Number1: ”
read num1
echo -n “Number2: ”
read num2
echo “$num1 – $num2 = $((num1-num2))”
enter ;;
3) clear
echo “Enter two numbers for Multiplication : ”
echo -n “Number1: ”
read num1
echo -n “Number2: ”
read num2
echo “$num1 * $num2 = `echo “$num1*$num2″|bc`”
enter ;;
4) clear
echo “Enter two numbers for Division : ”
echo -n “Number1: ”
read num1
echo -n “Number2: ”
read num2
let div=num1/num2
echo “$num1 / $num2 = $div”
enter ;;
5) exit_function ;;
*) echo “You entered wrong option, Please enter 1,2,3,4 or 5″
echo “Press enter to continue”
read
clear
esac

done

Output:-

Capture

shell scripting in linux

What is Linux ?
Linux is an open-source operating system modelled on UNIX.

What is Shell Script ?

A shell script is a computer program designed to be run by the Unix shell, a command line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text.

Different types of shell in linux ?
Bourne shell (sh)
C shell (csh)
TC shell (tcsh)
Korn shell (ksh)
Bourne Again SHell (bash)

I like Bourne shell(sh), you will find many of my scripts in sh.

Bourne shell (sh):
—————————————————————————————
This is the original Unix shell written by Steve Bourne of Bell Labs. It is available on all UNIX systems.The Bourne shell does provide an easy to use language with which you can write shell scripts.

Purpose of Shell script ?
Many a times we do repetitive work, for example.
1. Taking Database dumps
2. Generating Reports
3. Configuration Backup’s etc..

The above tasks can be automated with the help of scripting.

Writing your first script and getting it work!!

————————————————————————————————

To successfully write a shell script, you have to do three things:

1. Write a script
2. Give the shell permission to execute it
3. Put it somewhere the shell can find it

Writing Script :-
——————————————————————————————
A shell script is a file that contains ASCII text. To create a shell script, we can use a text editor.
A text editor is a program, like a word processor, that reads and writes ASCII text files.
There are many text editors available for your Linux system, both for the command line environment and the GUI environment.
Here is a list of some common ones:
vi
vim
nano
gedit etc.

Writing your first script
————————–
vim myfirstscript.sh
#!/bin/bash
#My First Script to print text
#Author : xyz
#Developed Date : dd/mm/yyyy
echo “Hello, This is my first script”
——————————————–
save and exit.

Give executable permissions,
chmod 755 myfirstscript.sh

we can run the script in two ways,
1. sh myfirstscript.sh
2. ./myfirstscript.sh

After running script, you should see “Hello, This is my first script” . you have just wrote a simple shell script and it worked!!