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LFCS · Question #653

What does the ! mean when used at the beginning of a line in the username map file?

The correct answer is B. To stop processing the file if there is a match. In a Samba username map file, the exclamation mark (!) at the beginning of a line signifies that if a match is found for that entry, no further processing of the map file should occur for the current mapping request.

Submitted by noor.lb· Apr 18, 2026User and Group Management

Question

What does the ! mean when used at the beginning of a line in the username map file?

Options

  • AThat account has been disabled.
  • BTo stop processing the file if there is a match.
  • CIt indicates that it is a system group, not a username.
  • DIt is a comment.

How the community answered

(52 responses)
  • A
    2% (1)
  • B
    88% (46)
  • C
    6% (3)
  • D
    4% (2)

Why each option

In a Samba username map file, the exclamation mark (!) at the beginning of a line signifies that if a match is found for that entry, no further processing of the map file should occur for the current mapping request.

AThat account has been disabled.

An exclamation mark does not disable an account; it controls the processing flow of the username map file itself to prevent unintended subsequent matches.

BTo stop processing the file if there is a match.Correct

When Samba encounters an entry beginning with '!' in the username map file and finds a match for the username, it will immediately stop processing subsequent lines in the file for that mapping, ensuring that only the first matching rule with '!' is applied.

CIt indicates that it is a system group, not a username.

The '!' character is not used to distinguish system groups from usernames; it is a control character for defining mapping precedence and termination.

DIt is a comment.

While '#' is typically used for comments in configuration files, '!' has a specific functional meaning in the username map file to stop processing.

Concept tested: Samba username map file syntax

Topics

#User Mapping#Configuration Syntax#Rule Processing#Identity Management

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