Day 5 of 90 Days of DevOps Challenge: Linux Basic Commands

On Day 4, I explored the fundamentals of the Linux Operating System, its architecture, and how it manages processes and resources using the kernel and shell. I also walked through setting up a Linux environment on AWS EC2, giving me hands-on experience with cloud-based systems.

Today, I’m taking the next step, getting comfortable with basic Linux commands. These commands form the foundation for working efficiently in the terminal and are essential for system navigation, file handling, and overall productivity in local and cloud environments.

How to get started

Now that our environment is set up, we can begin practicing Linux commands right from our terminal. Simply use the ssh command with your .pem key file and the public IP of your EC2 instance like this:

ssh -i /path/to/your-key.pem ec2-user@ec2-public-ip

Basic Linux Commands

ls → List the files and directories

ls -l → Long listing of all directory files (in alphabetical order)

ls -l dirname → Content inside the directory

ls -lr → Reverse alphabetical order

ls -lt → Displays the latest files on top

ls -ltr → Old files on top

ls -la → Displays hidden files

pwd →Present working directory

clear → Clears the terminal

whoami → Username details

date → Day

cal → Date with month calendar

history → Command history

cd dirname → Change directory

cd .. → Go to previous directory

cd ~ → Switch to home directory

mkdir dirname→ Create directory

rmdir dirname → Delete directory if it is empty

rm filename→ Delete file

rm * → Remove all the files in directory

rm -rf dirname → Delete non-empty directory

mv filename newfilename → Rename file

mv filename dirname/filename → Move file from one location to another

touch filename→ Create empty files

cat > filename → Create and add content

cat >> filename → Append data

cat filename → Print file content

cat file_1 file_2 > file_3 → Copy more than one file data into another file

cat -n filename → Print data with line numbers

tac filename →Print file data from bottom to top

rev filename → Reverses each line of data

cp fileone filetwo → Copy file data from one to another

wc filename→ Word count (no of lines, words, chars)

cmp fileone filetwo → Compare files

diff fileone filetwo→ Check differences

head filename → Prints only first 10 lines(default) from the file

head -n 5 filename → Print 5 lines from top

tail filename→ prints the last 10 lines from the file

tail -n 5 filename → Print 5 lines from the bottom

tail -f filename → Get the live data (newly added)

grep 'word' filename → Global regular expression print → case sensitive command

grep -i 'word' filename → Search a word (except case sensitivity)

grep -i 'word' * → Searches the word in all the files

grep -n 'word' filename → Print lines having word with line number

grep -v 'word' filename → Skips the line containing that word & prints all other content from the file

NOTE : We can use a combination of any option.

vi filename→ visual editor, can create and modify file data → Three Modes → command mode (open file) → insert mode (press i) → exit mode (esc + :wq! (to save), esc + q!(unsave and exit))

nano filename→ create file and add data into it → Two Modes → command mode (just open file) → exit mode (ctrl + x + y(to save), ctrl + x + n(unsave and exit))

sed → Stream editor, used to substitute, modify and delete the data

sed 's/word1/word2/' filename → Change /replace first occurance of word

sed 's/word1/word2/2' filename → Change /replace second occurance of word

sed 's/word1/word2/g' filename → Change /replace all of occurrences of word with the second

sed -i 's/word1/word2/g' filename → Save changes permanently

sed '4d' filename → Delete line

sed '$d' filename → Delete last line

sed '3, $d' filename → Delete 3rd to last line

sed -i '4d' filename → Delete line from the file permanently

sed '/word/p' filename → Print line twice containing a word

sed '/word/d' filename → Delete line containing a word

sed -n '3,6p' filename → Print data 3rd line to 6th line

sed '4i/data' filename → Insert a data before 4th line

sed '$a/data' filename → Insert a data after the line

awk → Perform ops on files containing structured data, also called a filter command

awk '/word/ {print}' filename → Print data with certain word in it

awk '{print $3, $7}' filename → Print data from column 3 and 7

awk '{print NR, $0}' filename → Print data with record number

awk '{print NR, $0} filename → Print file data with line numbers

awk '{print NR "-" $1} filename → Print first col data with line numbers and -

awk '{print NR "@" $1} filename → Print first col data with line numbers and @

Final thoughts

Getting hands-on with Linux is a key step in the DevOps journey. From managing files and directories to using tools like sed and awk, today’s session laid the foundation for real-world system tasks.

These basics are crucial for working confidently on cloud platforms like AWS, where Linux powers most infrastructure.

Stay tuned as I continue exploring Linux in upcoming posts. If you're also following the #90DaysOfDevOpsChallenge, keep practicing.

Let’s keep learning and growing together!