In permission settings, which mode uses octal numbers to specify permissions?

The correct choice is absolute mode, which utilizes octal numbers to specify permissions. In Linux, file permissions can be set using either symbolic or absolute methods.

In absolute mode, permissions are represented by three octal digits, each ranging from 0 to 7. These digits correspond to the read, write, and execute permissions for the owner, group, and others. The octal numbers are summed based on the basic permission values: read is represented by 4, write by 2, and execute by 1. This allows for a concise representation, making it easy to set complex permission combinations using a single three-digit number.

For instance, a permission setting of 755 indicates that the owner has read (4), write (2), and execute (1) permissions (total of 7), while the group and others have read and execute permissions (4 + 1 = 5). This clear mapping between octal values and corresponding permissions is a key feature of absolute mode, which distinguishes it from other modes like symbolic mode, which utilizes letters to set permissions rather than numeric values.