010-160 · Question #10
What is the UID of the user root?
The correct answer is E. 0. The root superuser account is always assigned UID 0 on Linux and Unix-like systems, and this value is what the kernel uses to grant unrestricted privileges.
Question
Options
- A1
- B-1
- C255
- D65536
- E0
How the community answered
(21 responses)- B5% (1)
- C5% (1)
- E90% (19)
Why each option
The root superuser account is always assigned UID 0 on Linux and Unix-like systems, and this value is what the kernel uses to grant unrestricted privileges.
UID 1 is typically assigned to the first non-root system account such as 'daemon' or 'bin', not to the root account.
UIDs are unsigned integers on Linux; negative values are not valid and cannot be assigned to any user.
UID 255 falls within the range commonly used for system or service accounts, not for the root superuser.
UID 65536 exceeds the traditional 16-bit UID space and is sometimes used as a sentinel value for 'nobody', not for root.
UID 0 is reserved exclusively for root by POSIX convention and is hardcoded into the kernel's privilege model. The kernel checks the numeric UID 0 - not the string 'root' - when determining superuser access, so any account assigned UID 0 inherits full system privileges regardless of its login name.
Concept tested: Root user UID 0 assignment in Linux
Source: https://man7.org/linux/man-pages/man5/passwd.5.html
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