LFCS Question #743: Real Exam Question with Answer & Explanation

Question

Which of the following commands makes /bin/foo executable by everyone but writable only by its owner?

Options

• Achmod 557 /bin/foo
• Bchmod o+rwx.a+rx/bin/foo
• Cchown 557 /bin/foo
• Dchmod 755/bin/foo

Explanation

The chmod 755 /bin/foo command sets file permissions so the owner has read, write, and execute permissions (7), while group and others have read and execute permissions (5), satisfying the requirement.

Common mistakes.

• A. chmod 557 would make the file readable and executable by owner and group, but readable, writable, and executable by others, which is incorrect.
• B. The syntax o+rwx.a+rx is incorrect; the correct syntax for adding permissions would be o+rwx,a+rx.
• C. chown changes file ownership, not permissions, making it irrelevant to the question's requirement.

Concept tested. Linux file permissions (chmod octal)

Reference. https://learn.microsoft.com/en-us/windows-server/administration/linux-reference/linux-commands/chmod

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