LPIC-1 Administrative Tasks Practice Question
In the /etc/shadow file, a user's password hash begins with '$6$'. What hash algorithm does this prefix indicate?
⚠ Common exam trap
It's easy for candidates to confuse the prefix '$6$' with SHA-256 (which uses '$5$') or mistakenly associate '$6$' with Blowfish due to similar numbering, but the correct mapping is $1$=MD5, $5$=SHA-256, $6$=SHA-512.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SHA-512
The prefix '$6$' in the /etc/shadow file indicates that the password hash was generated using the SHA-512 (Secure Hash Algorithm 512-bit) algorithm. This is defined in the crypt(3) function's modular crypt format, where $1$ is MD5, $5$ is SHA-256, and $6$ is SHA-512. SHA-512 is the strongest of the commonly used hash algorithms in Linux password hashing, providing a 512-bit digest.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
SHA-512
Why this is correct
$6$ corresponds to SHA-512.
- ✗
SHA-256
Why it's wrong here
SHA-256 is indicated by $5$.
- ✗
MD5
Why it's wrong here
MD5 is indicated by $1$.
- ✗
Blowfish
Why it's wrong here
Blowfish is indicated by $2a$ or $2b$.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-1 practice question is part of Courseiva's free LPI certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LPIC-1 exam.