System information: Adding colors to Shell script

#!/bin/bash
# Sample script written for Part 4 of the RHCE series
# This script will return the following set of system information:
# -Hostname information:
echo -e "\e[31;43m***** HOSTNAME INFORMATION *****\e[0m"
hostnamectl
echo ""
# -File system disk space usage:
echo -e "\e[31;43m***** FILE SYSTEM DISK SPACE USAGE *****\e[0m"
df -h
echo ""
# -Free and used memory in the system:
echo -e "\e[31;43m ***** FREE AND USED MEMORY *****\e[0m"
free
echo ""
# -System uptime and load:
echo -e "\e[31;43m***** SYSTEM UPTIME AND LOAD *****\e[0m"
uptime
echo ""
# -Logged-in users:
echo -e "\e[31;43m***** CURRENTLY LOGGED-IN USERS *****\e[0m"
who
echo ""
# -Top 5 processes as far as memory usage is concerned
echo -e "\e[31;43m***** TOP 5 MEMORY-CONSUMING PROCESSES *****\e[0m"
ps -eo %mem,%cpu,comm --sort=-%mem | head -n 6
echo ""
echo -e "\e[1;32mDone.\e[0m"

Run this script in bash shell and you will get an output similar below.

Note that the headers of each section are shown in color for better visualization:

That functionality is provided by this command:

echo -e "\e[COLOR1;COLOR2m<YOUR TEXT HERE>\e[0m"

Where COLOR1 and COLOR2 are the foreground and background colors, respectively (more info and options are explained in this entry from the Arch Linux Wiki) and <YOUR TEXT HERE> is the string that you want to show in color.

Enable direct ssh access to EC2 instance without .pem key

Enable password authentication by editing /etc/ssh/sshd_config: change PasswordAuthentication no to PasswordAuthentication yes

Restart ssh:

sudo /etc/init.d/ssh restart

systemctl  restart sshd (for RHEL7)

Ansible : Privilege escalation (become)

Ansible uses the become, become_user, and become_method directives to achieve privilege escalation. You can apply them to an entire play or playbook, set them in an included playbook, or set them for a particular task.

- name: checkout repo
  git: repo=https://github.com/some/repo.git version=master dest={{ dst }}
  become: yes
  become_user: some_user

You can use become_with to specify how the privilege escalation is achieved, the default being sudo.

More Examples:

- name: Ensure the httpd service is running
  service:
    name: httpd
    state: started
  become: yes

To run a command as the apache user:

- name: Run a command as the apache user
  command: somecommand
  become: yes
  become_user: apache

To do something as the nobody user when the shell is nologin:

- name: Run a command as nobody
  command: somecommand
  become: yes
  become_method: su
  become_user: nobody
  become_flags: '-s /bin/sh'

Setting up Ansible in AWS Linux RHEL

Enable PING
Edit Security Groups>Add Rule>>ICMP

Connect to AWS using putty
Follow the steps mentioned here/
https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/putty.html

To convert the .pem to .ppk file use the latest PuttyGen otherwise you will encounter the issues like 'Cant load the private key'

Modify the shell prompt

vi /etc/bashrc
Edit the below line as you like
[ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@MyServer>\w]\\$ "

Enable Root Login in AWS Linux machine

Uncomment PermitRootLogin in /etc/ssh/sshd_config

Setup SSH Passwordless authentication

copy the generated .pem file to he server using winscp (if you are using windows)
1. As root run ssh-keygen (generate the key to id_rsa.pub)
2. As ec2-user copy this file to Target server:/home/ec2-user
scp -i "/home/ec2-user/clients.pem" /root/.ssh/id_rsa.pub ec2-user@x.x.x.x:/home/ec2-user/
2. Login to target Server
    cat /home/ec2-user/id_rsa.pub >> /root/.ssh/authorized_keys

Now you have setup the SSH passwordless login for Ansible.

Daily Task Automation: High load notification

The below code will trigger an email if the load is higher than 5

load=`w | head -n1 | awk '{print$10}' | cut -d"," -f1`
if [ $load -gt 5 ]; then
echo "High Load Found." | mail -s "High Load Found."  mail@example.com
fi

Ansible - wait_for module

wait_for - Waits for a condition before continuing

EXAMPLES

- name: sleep for 300 seconds and continue with play
wait_for: timeout=300
delegate_to: localhost


- name: Wait 300 seconds for port 8000 to become open on the host, don't start checking for 10 seconds
wait_for:
port: 8000
delay: 10


- name: Wait 300 seconds for port 8000 of any IP to close active connections, don't start checking for 10 seconds
wait_for:
host: 0.0.0.0
port: 8000
delay: 10
state: drained


- name: Wait 300 seconds for port 8000 of any IP to close active connections, ignoring connections for specified hosts
wait_for:
host: 0.0.0.0
port: 8000
state: drained
exclude_hosts: 10.2.1.2,10.2.1.3


- name: Wait until the file /tmp/foo is present before continuing
wait_for:
path: /tmp/foo


- name: Wait until the string "completed" is in the file /tmp/foo before continuing
wait_for:
path: /tmp/foo
search_regex: completed


- name: Wait until the lock file is removed
wait_for:
path: /var/lock/file.lock
state: absent


- name: Wait until the process is finished and pid was destroyed
wait_for:
path: /proc/3466/status
state: absent


- name: Output customized message when failed
wait_for:
path: /tmp/foo
state: present
msg: Timeout to find file /tmp/foo

Monitoring script & html output

Here we are monitoring the file system usage by 'df -h' command and output of this command can be accessible via web browser.

#!/bin/bash
# Sample script to demonstrate the creation of an HTML report using shell scripting
# Web directory
df -h > /var/www/html/test.txt
WEB_DIR=/var/www/html
# A little CSS and table layout to make the report look a little nicer
echo "<HTML>
<HEAD>
<style>
.titulo{font-size: 1em; color: white; background:#0863CE; padding: 0.1em 0.2em;}
table
{
border-collapse:collapse;
}
table, td, th
{
border:1px solid black;
}
</style>
<meta http-equiv='Content-Type' content='text/html; charset=UTF-8' />
</HEAD>
<BODY>" > $WEB_DIR/report.html
# View hostname and insert it at the top of the html body
HOST=$(hostname)
echo "Filesystem usage for host <strong>$HOST</strong><br>
Last updated: <strong>$(date)</strong><br><br>
<table border='1'>
<tr><th class='titulo'>Filesystem</td>
<th class='titulo'>Size</td>
<th class='titulo'>Use %</td>
</tr>" >> $WEB_DIR/report.html
# Read the output of df -h line by line
while read line; do
echo "<tr><td align='center'>" >> $WEB_DIR/report.html
echo $line | awk '{print $1}' >> $WEB_DIR/report.html
echo "</td><td align='center'>" >> $WEB_DIR/report.html
echo $line | awk '{print $2}' >> $WEB_DIR/report.html
echo "</td><td align='center'>" >> $WEB_DIR/report.html
echo $line | awk '{print $5}' >> $WEB_DIR/report.html
echo "</td></tr>" >> $WEB_DIR/report.html
done < /var/www/html/test.txt
echo "</table></BODY></HTML>" >> $WEB_DIR/report.html

Open the report.html file in a web browser. You will see output similar to below.

You can add to that report as much information as you want. To run the script every day at 1:30 pm, add the following crontab entry:

30 13 * * * /root/scripts/filesystem_usage.sh