Disk usage summary on Unix/Linux: Which command is used to summarize per-file and per-directory disk space consumption for quick assessment?

Introduction / Context:
Administrators frequently need to identify which directories or files consume space. Unix provides standard utilities to summarize disk usage efficiently, assisting in cleanup, quota checks, and capacity planning.

Given Data / Assumptions:

• We are in a Unix/Linux environment.
• The goal is to summarize disk usage by directory and file.
• Only standard command names are considered; no third-party tools.

Concept / Approach:

The du command (disk usage) reports the number of blocks or human-readable sizes used by files and directories. Options like -s (summary) and -h (human-readable) are common combinations. Other listed commands are from different ecosystems or serve different purposes.

Step-by-Step Solution:

Verification / Alternative check:

Running du -sh /var/ quickly reveals which subdirectories occupy the most space. This is the canonical approach for Unix-like systems.

Why Other Options Are Wrong:

• chkdsk: DOS/Windows filesystem checking tool, not a Unix usage reporter.
• fdisk: Partition table editor; unrelated to per-directory usage.
• disk: Not the standard tool for usage in Unix.
• None of the above: Incorrect because 'du' is correct.

Common Pitfalls:

Confusing 'du' with 'df'. df reports filesystem-level free/used space; du drills down into directories and files. For complete analysis, both are useful together.

Final Answer:

du