GCFA · Question #201
You work as a Network Administrator for Perfect Solutions Inc. The company has a Linux-based network. You are creating a user account by using the USERADD command. Which of the following entries…
The correct answer is A. 0 B. 99 D. -1. The useradd command reserves certain UID ranges for the system, and negative UIDs are invalid, making UIDs 0, 99, and -1 ineligible for regular user accounts.
Question
You work as a Network Administrator for Perfect Solutions Inc. The company has a Linux-based network. You are creating a user account by using the USERADD command. Which of the following entries cannot be used for specifying a user ID? Each correct answer represents a complete solution. Choose all that apply.
Options
- A0
- B99
- C100
- D-1
How the community answered
(35 responses)- A77% (27)
- C23% (8)
Why each option
The useradd command reserves certain UID ranges for the system, and negative UIDs are invalid, making UIDs 0, 99, and -1 ineligible for regular user accounts.
UID 0 is exclusively reserved for the root superuser account and cannot be assigned to a regular user via useradd.
UIDs 1 through 99 are conventionally reserved for system accounts and daemons, making 99 unavailable for regular user creation.
UID 100 falls within the range available for regular user accounts (typically 100 or 1000 and above depending on distribution), so it is a valid choice for useradd.
Negative integers such as -1 are not valid UID values - UIDs must be non-negative integers, so -1 is rejected by the useradd command.
Concept tested: Linux useradd reserved UID ranges and validity
Source: https://man7.org/linux/man-pages/man8/useradd.8.html
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