How to Use Symbolic Mode with chmod

How to Use Symbolic Mode with chmod

Welcome to this beginner-friendly Linux tutorial! Today, we’re learning how to change file permissions using symbolic mode with the chmod command.

Don't worry if you've never used chmod before. We’ll go step-by-step and use real examples so that it’s easy to follow.

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🔍 What is chmod?

The chmod command is used to change the permissions of files and directories in Linux. Permissions decide who can read, write, or execute a file.

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📘 Understanding Symbolic Mode

In symbolic mode, we use letters and symbols to describe permissions:

• u = user (owner)
• g = group
• o = others
• a = all (u+g+o)

Then we use operators:

• + = add permission
• - = remove permission
• = = set exact permission

And finally, permission types:

• r = read
• w = write
• x = execute

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🛠️ Let's Practice!

Step 1: Create a sample file

touch demo.txt

Step 2: Check the current permissions

ls -l demo.txt

-rw-r--r-- 1 user user 0 Jul  2 10:00 demo.txt

This means the owner can read and write, and group/others can only read.

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🔧 Add execute permission for the user

chmod u+x demo.txt

Check again:

ls -l demo.txt

-rwxr--r-- 1 user user 0 Jul  2 10:00 demo.txt

Now the user has execute permission too.

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➖ Remove read permission from others

chmod o-r demo.txt

ls -l demo.txt

-rwxr----- 1 user user 0 Jul  2 10:00 demo.txt

Others can no longer read the file.

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🔄 Set group permissions to exactly read and execute

chmod g=rx demo.txt

ls -l demo.txt

-rwxr-x--- 1 user user 0 Jul  2 10:00 demo.txt

The group now has only read and execute permissions.

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📌 Tip: Use a to affect all

chmod a-w demo.txt

ls -l demo.txt

-r-xr-xr-- 1 user user 0 Jul  2 10:00 demo.txt

This removes write permission from everyone.

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🎉 Recap

• chmod in symbolic mode is readable and intuitive
• Use u, g, o, a to choose who you're modifying
• Use +, -, = to set permissions
• Use r, w, x to define permission types

Practice with different combinations and try it out on both files and directories!

That’s it for this tutorial! 🚀