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' has a umask of 027 in her .bashrc, but the system administrator wants to enforce a umask of 007 for all users in the 'staff' group. Where should the administrator place the umask command to ensure it cannot be overridden by users?
/etc/bash.bashrc
Why wrong: Users can override in their .bashrc.
/etc/skel/.bashrc
Why wrong: Only affects new users; existing users not changed.
/etc/profile
Why wrong: Users can override in their .bash_profile.
In /etc/pam.d/common-session with pam_umask.so
PAM umask module applies the umask regardless of shell scripts.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
In /etc/pam.d/common-session with pam_umask.so
Option C is correct: /etc/bash.bashrc is sourced before user files, but users can still override? Actually, the safest is to use /etc/profile.d/ with a script, but the question asks for a location that cannot be overridden? Typically, /etc/bash.bashrc is for all bash users, but users can still override in their .bashrc after it. The only way to enforce is to set umask in /etc/profile or /etc/bash.bashrc and also in /etc/skel/.bashrc, but users can still change. Actually, no shell-level enforcement is absolute; root can set it in a login script that runs after user scripts? But the question is tricky. I'll set the correct answer to a pam module: option D: using pam_umask.so in /etc/pam.d/common-session. That ensures it is applied regardless of shell configuration. So D is correct. Other options are overrideable.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
/etc/bash.bashrc
Why it's wrong here
Users can override in their .bashrc.
/etc/skel/.bashrc
Why it's wrong here
Only affects new users; existing users not changed.
/etc/profile
Why it's wrong here
Users can override in their .bash_profile.
In /etc/pam.d/common-session with pam_umask.so
Why this is correct
PAM umask module applies the umask regardless of shell scripts.
Related concept
CIDR notation defines the prefix length.
Common exam traps
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
What to study next
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related LFCS subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
User and Group Management — This question tests User and Group Management — CIDR notation defines the prefix length..
The correct answer is: In /etc/pam.d/common-session with pam_umask.so — Option C is correct: /etc/bash.bashrc is sourced before user files, but users can still override? Actually, the safest is to use /etc/profile.d/ with a script, but the question asks for a location that cannot be overridden? Typically, /etc/bash.bashrc is for all bash users, but users can still override in their .bashrc after it. The only way to enforce is to set umask in /etc/profile or /etc/bash.bashrc and also in /etc/skel/.bashrc, but users can still change. Actually, no shell-level enforcement is absolute; root can set it in a login script that runs after user scripts? But the question is tricky. I'll set the correct answer to a pam module: option D: using pam_umask.so in /etc/pam.d/common-session. That ensures it is applied regardless of shell configuration. So D is correct. Other options are overrideable.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related LFCS subnetting questions on CIDR, address ranges, and subnet selection.
CIDR notation defines the prefix length.
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Last reviewed: Jun 24, 2026
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