Let's start our first task:

1. Create a series of directories with the help of a shell script using run-time arguments.

Question: Why do we need to create these kinds of directories:

The answer is, suppose we got a request to create 100 directories in a particular location. It will be a very time taking task and maybe we made some mistakes right? so reduce the time and get the accuracy we used shell script.

Now let's jump to our terminal and create a shell script for the same.

$ sudo nano runtargs.sh

#!/bin/bash

# Check if the arguments are 3 or not.

if  [ "$#" -ne 3  ]
then

echo "Usage: $0 dir_name start_num end_num "

exit 1

fi

# Define the arguments  to variables

dir_name="$1"
start_num="$2"
end_num="$3"

#loop through by the range of directory numbers

for (( i="$start_num"; i<="$end_num"; i++  ));

do 

mkdir "$dir_name$i"

done

echo "Your directories are created below"

ls

Now run the script.

$ ./runtargs.sh 
Usage: ./runtargs.sh dir_name start_num end_num 

Now pass the arg.

$ ./runtargs.sh file 1 10

Your directories are created below
file1  file10  file2  file3  file4  file5  file6  file7  file8    file9

Now let's move to our next task:

1. Create a Backup of my above work

We have a directory called "scripting" and want to take a backup of this directory and want to move it to another path for example I will use the target path of my backup "/backup" from "/prod/scripting" and I want to use the backup file name as today's date

Now let's jump to the terminal.

# create a bkp.sh file
sudo nano bkp.sh

Now write down below code

#!/bin/bash  #these tags are script starting tag

src_dir=/prod/scripting   #souce of the directory
tgt_dir=/backup           #target/destination of backup file     

# now get current time stamp by below commands 
current_timestamp=$(date "+%Y"-"+%m"-"+%d"-"+%H"-"+%M"-"+%S") 
#defining backup file name and taking backup
backup_file=$tgt_dir/$current_timestamp.tgz

echo "Taking backup on $current_timestamp"


echo "$backup_file"

#Now create a tar file to compress it.

tar czf $backup_file --absolute-names  $src_dir 

echo "Backup Completed"

Here is the output.

/backup# la
2023-+04-+01-+15-+09-+10.tgz

Now let's do our last task making these tasks automate by a shell script.

1. Automate these tasks

Before automating the task let's discuss what is cron and crontab.

CRON: Cron is a time-based job scheduler in Unix-like operating systems, which can automatically execute commands or scripts at specified times or intervals. Cron is commonly used for scheduling repetitive tasks, such as backups, system maintenance, and automated tasks.

CRONTAB: A crontab file is a simple text file that contains a list of commands meant to be run at specified times. The crontab command is used to create, modify, and manage the crontab files for individual users. Each line of the crontab file specifies a command or script to run, along with a schedule for when it should be run. The syntax for each line is as follows:

*     *     *   *    *     command to be executed every minute
-     -     -   -    -
|     |     |   |    |
|     |     |   |    +----- day of the week (0 - 6) (Sunday=0)
|     |     |   +------- month (1 - 12)
|     |     +--------- day of the month (1 - 31)
|     +----------- hour (0 - 23)
+------------- min (0 - 59)

Now let's automate both above tasks and jump to the terminal and crontab.

$ crontab -e
# paste below code at the of the file.
* * * * * /prod/scripting/bkp.sh

* * * * * /prod/scripting/runtargs.sh file 11 13

Here is the backup

/backup# ls 2023-+04-+01-+15-+09-+10.tgz

Here are the new directories.

file11  file12  file13

User Management:

In Linux, user management involves creating, modifying, and deleting user accounts and groups. Here are some commonly used commands for user management in Linux:

1. useradd: The "useradd" command is used to create a new user account.

2. passwd: The "passwd" command is used to set or change a user's password.

   Here are some common options for the "passwd" command:

   • "-l": Lock the user's account.

   • "-u": Unlock the user's account.

   • "-d": Remove the user's password.

Create 2 users and just display their Usernames:

1. To add a user to the Linux system:

useradd devops

1. setting user password:

passwd devops

1. If we want to add a user by making a directory use the -m flag

2. sudo useradd devops -m

   -d dir	Set the user’s home directory to be dir.
   -s shell	Set the user’s login shell to be shell.
   -u uid	Set the user’s ID to be uid. Unless you know what you’re doing, omit this option and accept the default.
   -g group	Set the user’s initial (default) group to group, which can either be a numeric group ID or a group name, and which must already exist.
   -G group1,group2,…	Make the user a member of the additional, existing groups group1, group2, and so on.
   -m	Copy all files from your system skeleton directory, /etc/skel, into the newly created home directory. The skeleton directory traditionally contains minimal (skeletal) versions of initialization files, like ~/.bash_profile, to get new users started If you prefer to copy from a different directory, add the -k option (-k your_preferred_directory).

3. To check whether the user added or not if the user added where it should be present:

   sudo cat /etc/passwd

Thank you for reading this Blog. Hope you learned something new today! If you found this blog helpful, please like, share, and follow me for more blog posts like this in the future.