What is true about the option create mask in smb.conf?

Question

Options

• AEach permission bit that is set (1) in create mask cannot be set on a file created by Samba even if
• BEach permission bit that is cleared (0) in create mask is only set on a file created by Samba if the
• CEach permission bit that is cleared (0) in create mask is always cleared on a file created by
• DEach permission bit that is set (1) in create mask is always set on a file created by Samba
• EWhen both create mask and create mode are specific for a share, create mask is ignored.

• A
  10% (3)
• B
  3% (1)
• C
  79% (23)
• D
  7% (2)

Explanation

create mask works as a bitwise AND filter applied to file permissions when Samba creates files. Because of this AND operation, any bit that is 0 in the mask will force the corresponding permission bit to 0 in the resulting file - unconditionally - making C correct.

Why the distractors are wrong:

• A reverses the logic: bits set to 1 in create mask are permitted (they pass through the AND), not blocked.
• B is wrong because 0 bits are not "conditionally" cleared - they are always cleared; there is no circumstance under which a masked-out bit gets set.
• D confuses "allowed" with "guaranteed": a 1 in create mask means the bit can be set, but only if the underlying permission also requests it - it is not forced on.
• E is false: create mask (AND mask, removes bits) and force create mode (OR mask, adds bits) are both applied together; neither is ignored when both are present.

Memory tip: Think of create mask as a net with holes. Wherever the net has a 0 (solid patch), no permission can pass through - ever. Wherever it has a 1 (hole), the permission might pass through, depending on what was requested.

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