Day 5 - Advanced Linux Shell Scripting for DevOps Engineers with User management

Creating n number of directories using shell script

vi directories.sh

#!/bin/bash
for num in {1..4}
do
mkdir folder$num
done
echo "Directories created sucessfully"

#!/bin/bash
for num in {1..4}
do
echo $num #prints the count
done

Creating n number of directories using for loop iteration

vi forloopiteration.sh raju

1. 

   Script to Backup files

   nano backupscript.sh

    #!/bin/bash
    src=/c/Users/Rj/Downloads/nginx
    tgt=/c/Users/Rj/Downloads/shell
    filename=nginxbackup
    tar -czvf $tgt/$filename.tar.gz $src
    echo "backup done sucessfully"
   

   sh backupscript.sh

2. 

   xargs command is used to bring entire arguments in a single line

   

    cat <filename> | xargs
   

   awk command to print the specified columns from date

   

   We can also take a backup by using the date

   nano backupscript.sh

    #!/bin/bash
    src=/c/Users/Rj/Downloads/nginx
    tgt=/c/Users/Rj/Downloads/shell
    filename=$(date | xargs | awk '{print $2"-"$3"-"$6}')
    tar -czvf $tgt/$filename.tar.gz $src
    echo "backup done sucessfully"
   

   

   Crontab, to automate the backup Script

   Open the Terminal

   $ crontab -e

3. 

   */5 * * * * is to run the script every 5 mins

   control+X and y enter

   

   your script is ready for automation for every 5 mins

Creating Multiple Users

sudo useradd tom
sudo useradd jerry
id tom
id jerry
To view all the users 
$ sudo cat /etc/passwd

---

Loop to find a file or directory in the present working directory

nano loop.sh

#!/bin/bash
for num in /*
do
echo $num
done

nano loop1.sh

#!/bin/bash
for num in /c/Users/Rj/Downloads/shell/*
do
echo $num
done

#!/bin/bash
for num in $1/*
do
echo $num
done

sh loop1.sh /c/Users/Rj/Downloads/shell

Some Linux commands to check

nproc    # No of VMs
df -h    # Free space
df -a    # Free space
free -h  # Free Space
top      # Memory utilization
uname -m # arm configuration
last     # Complete details of user histroy
lastlogs # Give the lastlogin user details

df -h # Free space
df -h | awk '{print $2,$4}'
df -h | xargs | awk '{print $1 "-" $2}'

Shell scripting Mini Project

#!/bin/bash
echo "#################Shell Script assignment###################"
echo "Welcome to Devops, by user: $(whoami)"
echo "Today date is:"
date | awk '{print $3"-"$2"-"$6}'
echo "Time is:"
date | awk '{print $4}'

echo "************************************************************"
echo "Server uptime is:"
uptime
echo "Top $1 last logins:"
last -a | head -$1

echo "*************************************************************"
echo "My Server Utilization:"
df -h | xargs | awk '{print "Free Disk space is:" $11}'
df -h | xargs | awk '{print "Total Disk space is:" $9}'
df -h | xargs | awk '{print "Used Disk space is:" $10}'

echo "*************************************************************"
echo "My Server RAM(Memory) Utilization:"
free -h | xargs | awk '{print "Free Memory is:" $10}'
free -h | xargs | awk '{print "Total Memory is:" $8}'
free -h | xargs | awk '{print "Used Memory is:" $9}'

echo "*************************************************************"
echo "Top $2 CPU Processess running:"
top -b | head -$2

Output:

You can also write like this alternatively