Linux Professional Institute Certification Level 1 LPIC-1 LPIC-1 Questions 526–527 | Page 8/8

526

MCQmedium

An administrator notices that a large file on an ext4 filesystem is taking up more disk space than expected based on its size. Which command would show the actual disk usage (block allocation) of the file?

A.ls -l

B.df -h

C.du -h

D.stat

AnswerC

du -h displays disk usage in human-readable format for files and directories.

Why this answer

(du -h) is correct because du (disk usage) reports the actual disk space consumed by a file, including allocated blocks, which can be larger than the file's logical size due to block size overhead, fragmentation, or sparse file handling. On ext4, the default block size is 4096 bytes, so a 1-byte file occupies 4096 bytes on disk, and du reflects this allocation.

Exam trap

The trap here is that candidates confuse logical file size (shown by ls -l) with actual disk block allocation, assuming they are identical, and overlook that du accounts for filesystem overhead like block size rounding and sparse file handling.

How to eliminate wrong answers

Option A (ls -l) is wrong because it shows the logical file size (st_size), not the actual disk blocks allocated; it does not account for block size overhead or sparse file holes. Option B (df -h) is wrong because it reports filesystem-wide free and used space, not per-file disk usage. Option D (stat) is wrong because while it displays the file's size and blocks allocated (in 512-byte units), it does not directly show human-readable disk usage like du does; stat is more for inode metadata, not a quick usage summary.

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527

MCQhard

A database server on a Linux system is configured to listen on TCP port 3306. The administrator wants to restrict access to the database server to only the local network (192.168.1.0/24) using iptables. Which of the following iptables rules achieves this?

A.iptables -A INPUT -p tcp --dport 3306 -d 192.168.1.0/24 -j DROP

B.iptables -A OUTPUT -p tcp --dport 3306 -d 192.168.1.0/24 -j ACCEPT

C.iptables -A INPUT -p tcp --dport 3306 -s 192.168.1.0/24 -j ACCEPT

D.iptables -A OUTPUT -p tcp --sport 3306 -s 192.168.1.0/24 -j ACCEPT

AnswerC

Correct rule to allow incoming MySQL from local subnet.

Why this answer

It adds an INPUT chain rule that accepts TCP traffic destined for port 3306 only when the source address is within the 192.168.1.0/24 subnet. This effectively restricts incoming database connections to the local network, while all other sources are implicitly dropped by the default INPUT policy or subsequent rules.

Exam trap

The trap here is confusing the -s (source) and -d (destination) flags, leading candidates to pick Option A which drops traffic to the local network instead of accepting traffic from it.

How to eliminate wrong answers

Option A is wrong because it uses the -d (destination) flag instead of -s (source), and then jumps to DROP, which would block traffic destined for the 192.168.1.0/24 network (i.e., traffic going out to that subnet) rather than restricting incoming connections from it. Option B is wrong because it applies to the OUTPUT chain, which controls outgoing traffic; restricting access to an incoming database server requires an INPUT chain rule, not OUTPUT. Option D is wrong because it uses the OUTPUT chain with --sport 3306 (source port) and -s (source address), which would match outgoing packets originating from port 3306 with a source address in 192.168.1.0/24 — this is irrelevant for controlling incoming connections to the database server.

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Linux Professional Institute Certification Level 1 LPIC-1 (LPIC-1) — Questions 526–527