Linux · ACLs, Special Bits & Attributes

Why do security guides tell you to avoid the setuid bit when you can, and what protection does a setuid/setgid program remove?

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More in ACLs, Special Bits & Attributes

An unprivileged user runs passwd and successfully edits /etc/shadow, a file only root can write. How is that possible without giving the user root?

In ls -l you see -rwsr-xr-x on a binary. What does the s mean, what octal bit produced it, and how do you list every such program?

You add a setuid bit to a Python script hoping it will run as root. Why does it silently fail to give root privileges?

The setgid bit means one thing on an executable and something completely different on a directory. What are the two behaviors?

/tmp is world-writable, yet one user cannot delete another user's temp files. What mechanism enforces that?

In ls -l output, an uppercase S or T appears instead of a lowercase s or t. What does the capital letter signal?

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