Quick Answer
The answer is that the exclamation mark in the shadow password field means the account is locked. In the /etc/shadow file, the password field normally contains a hashed password, but when an administrator places a '!' at the start of that field—or replaces the hash entirely with '!'—the system interprets this as a lock that disables all password-based authentication. This is why user 'alice' cannot log in via SSH: the Linux authentication stack, including PAM, sees the '!' and immediately rejects any password attempt, even if the correct password is entered. On the Linux Foundation Certified System Administrator LFCS exam, this concept tests your understanding of account management and shadow file syntax, often appearing in troubleshooting scenarios where a user unexpectedly cannot authenticate. A common trap is confusing '!' with an expired password (which uses '!!' or a date-based flag), so remember: a single exclamation point is a hard lock, not a temporary disable. Memory tip: think of the exclamation mark as a "bang" that slams the door shut on the account.
This LFCS practice question tests your understanding of user and group management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user 'alice' is unable to log in via SSH. The administrator checks /etc/shadow and sees 'alice:!:19234:0:99999:7:::'. What does the '!' in the password field indicate?
The password must be changed at next login.
Why wrong: That is indicated by the last change field set to 0.
The account is disabled.
Why wrong: Disabled accounts often have '!!' or '*'.
The account is locked.
'!' is a common indicator of a locked account in /etc/shadow.
The password is expired.
Why wrong: Expired passwords are shown by a '!' at the start of the hash.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The account is locked.
The '!' in the password field of /etc/shadow indicates that the account is locked. This is a standard convention in Linux shadow password files: an exclamation mark placed before the hashed password (or replacing it entirely) disables password-based authentication, effectively locking the account. SSH login fails because the system refuses to authenticate any password attempt against a locked entry.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The password must be changed at next login.
Why it's wrong here
That is indicated by the last change field set to 0.
The account is disabled.
Why it's wrong here
Disabled accounts often have '!!' or '*'.
The account is locked.
Why this is correct
'!' is a common indicator of a locked account in /etc/shadow.
Related concept
Read the scenario before looking for a memorised answer.
The password is expired.
Why it's wrong here
Expired passwords are shown by a '!' at the start of the hash.
Common exam traps
The trap here is that candidates confuse 'account locked' (indicated by '!' in the password field) with 'password expired' (indicated by aging fields) or 'password must be changed at next login' (indicated by a last-change value of 0).
Trap categories for this question
Command / output trap
Expired passwords are shown by a '!' at the start of the hash.
Detailed technical explanation
In the /etc/shadow file, each field is colon-separated: username, password hash, last change, min age, max age, warning period, inactivity period, expiration date, and reserved. Placing a '!' at the start of the password hash (or as the entire field) prevents the system from matching any password, effectively locking the account while preserving the original hash for future unlocking. The 'usermod -L' and 'passwd -l' commands prepend this '!' to lock an account, and 'usermod -U' removes it to unlock.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
User and Group Management — study guide chapter
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FAQ
User and Group Management — This question tests User and Group Management — Read the scenario before looking for a memorised answer..
The correct answer is: The account is locked. — The '!' in the password field of /etc/shadow indicates that the account is locked. This is a standard convention in Linux shadow password files: an exclamation mark placed before the hashed password (or replacing it entirely) disables password-based authentication, effectively locking the account. SSH login fails because the system refuses to authenticate any password attempt against a locked entry.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
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