Change Ordinary Permission Bits

The teacher wants to edit the marks while allowing the report group to read them. Other users should receive no ordinary access from this file's mode. chmod changes permission bits so the access policy can match that intention.

Ownership answers who owns the file; permissions describe allowed operations for the applicable classes. Changing one does not automatically change the other. Let's set a deliberate mode and read the result rather than treating a bigger number as a generally better permission setting.

Prepare the example

Use a fresh practice folder and a file you own. The first line creates the exercise report. We will set its ordinary bits to 640, then inspect them. You do not need sudo merely to change the mode of your own eligible practice file.

Bash · Linux terminal

printf 'Diya: 72\n' > marks.txt
chmod 640 marks.txt
ls -l marks.txt

Expected behavior; machine-dependent details

The mode begins -rw-r-----; remaining listing fields vary.

chmod 640 marks.txt selects owner read/write, group read and no ordinary access for others. The digits identify permissions, not a new owner. The following ls -l displays the updated triplets and the owning user and group beside them.

Ask whether each granted operation matches the requirement. This example does not request execution, so adding execute bits just to remove an error would be unrelated. If another user still cannot read the report, inspect group membership, directory search access and any ACL or policy constraints. Broadening every bit can mask the actual explanation and give more access than the task needs.

chmod changes the permission bits on files and directories. You can describe the change with letters such as u+x or set the complete mode with numbers such as 755.

What Are File Permissions?

In Linux, every file and folder has permissions that determine who can read, write, or execute it. These permissions are categorized by:

• Owner – the person who created the file
• Group – a set of users who share access
• Others – everyone else

Check Current Permissions

Let’s check the permissions of a file using the ls -l command:

ls -l myscript.sh

-rw-r--r-- 1 user user 123 Jul  2 10:00 myscript.sh

This tells us:

• rw- — Owner can read and write
• r-- — Group can read
• r-- — Others can read

Using chmod to Change Permissions

▶ Symbolic Mode

Let's say you want to give execute permission to the owner:

chmod u+x myscript.sh

ls -l myscript.sh
-rwxr--r-- 1 user user 123 Jul  2 10:00 myscript.sh

What we did:

• u = user (owner)
• + = add permission
• x = execute

▶ Numeric Mode

You can also use numbers to set all permissions at once:

chmod 755 myscript.sh

ls -l myscript.sh
-rwxr-xr-x 1 user user 123 Jul  2 10:00 myscript.sh

This means:

• 7 = read + write + execute (owner)
• 5 = read + execute (group)
• 5 = read + execute (others)

Examples for Practice

Make a file readable and writable only by the owner:

chmod 600 secrets.txt

Make a script executable by everyone:

chmod a+x deploy.sh

Remove write permission from group:

chmod g-w report.txt

Verify Your Changes

Always check your work:

ls -l

Change permissions deliberately with chmod

So now you know:

• How to view file permissions
• How to use chmod in symbolic and numeric modes
• How to verify your changes with ls -l

Managing file permissions is a core skill in Linux. Practice often and you’ll master it in no time!

Your task: Does chmod change the file's owner?

Use a fresh practice folder and a file you own. The first line creates the exercise report. We will set its ordinary bits to 640, then inspect them. You do not need sudo merely to change the mode of your own eligible practice file.

Bash · complete example for this question

printf 'Diya: 72\n' > marks.txt
chmod 640 marks.txt
ls -l marks.txt

Expected behavior; machine-dependent details

The mode begins -rw-r-----; remaining listing fields vary.

Worked answer

No; it changes mode bits.

chmod changes mode bits, not the owning user. The value 640 encodes access choices. To change ownership, use the appropriate ownership command with its own authorization requirements; do not interpret the digits as user identifiers.

Translate the access requirement into specific bits, apply them and read them back. Keep ownership and directory traversal separate from the file's mode. The right setting is the one that grants the needed operations, not the broadest setting that happens to make an error disappear.