Web Server Rescue

Read-only, can be slow

Find Large Directories with du

You know a filesystem is full and need to identify which top-level directory is consuming the most space without crossing into other mounts.

Command

du -xh --max-depth=1 /var 2>/dev/null | sort -h

Before you run this

System impact: Read-only. Can create load on large logs, directories, filesystems, or process tables.

When not to use it: Do not start at `/` on a busy production system unless you have a reason. Keep the path narrow and stay on one filesystem.

Expected output

A size-sorted list of directories under `/var`, with the largest entries at the bottom because `sort -h` orders smallest to largest.

System impact

Read-only, can be slow. Nothing changes, but the scan can create disk I/O. The command measures directory sizes and sorts them.

May require elevated permissions on protected paths or service-owned files.

Scope this to the smallest useful path or service on busy systems.

Recovery / rollback: no state is changed.

When to use it

Use after `df -h` identifies the full mount and you need a folder-level map before inspecting individual files.

When not to use it

Do not start at `/` on a busy production system unless you have a reason. Keep the path narrow and stay on one filesystem.

Watch this command run

Command transcript

This sanitized transcript shows the commands and output shape without exposing host details.

demo@lab:~$

$ df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        25G   19G  5G  80% /work
tmpfs           982M   12M  970M   2% /run

$ du -xh --max-depth=1 /var 2>/dev/null | sort -h

24M	/var/tmp
180M	/var/cache
1.4G	/var/log
3.8G	/var/lib

View commands shown

These are the commands shown in the sanitized transcript.

Commands shown

df -h
du -xh --max-depth=1 /var 2>/dev/null | sort -h

next steps

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Study mapping

Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.