Linux Survival Basics

Read-only, can be slow

Find Which Folder Is Filling the Disk

A server is low on disk and you need a folder-level view before drilling into individual files.

Command

du -sh /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: Avoid assuming the largest folder is safe to delete; size is not ownership or importance. Scope the path more tightly on busy systems.

Expected output

A sorted list of directory sizes under `/var`, often pointing you toward logs, caches, backups, or application data.

System impact

Read-only, can be slow. Nothing changes on disk. The command prints human-readable folder 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.

When to use it

Use this before deeper `find` searches or cleanup decisions. It is a broad map, not the cleanup step.

When not to use it

Avoid assuming the largest folder is safe to delete; size is not ownership or importance. Scope the path more tightly on busy systems.

Recovery / rollback

No filesystem state is changed. If the scan is too slow, stop it with Ctrl-C and rerun against a narrower path.

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            64M     0   64M   0% /dev
shm              64M     0   64M   0% /dev/shm
tmpfs            64M     0   64M   0% /tmp
tmpfs            64M  352K   64M   1% /var
/dev/vda1        25G   19G  5G  80% /work
tmpfs            63G     0   63G   0% /proc/asound
tmpfs            63G     0   63G   0% /proc/acpi
tmpfs            63G     0   63G   0% /proc/scsi
tmpfs            63G     0   63G   0% /sys/firmware
tmpfs            63G     0   63G   0% /sys/devices/virtual/powercap

$ du -sh /var/* 2>/dev/null | sort -h

64K	/var/backups
96K	/var/log
192K	/var/cache

$ du -sh /var/log /var/cache /var/backups 2>/dev/null

96K	/var/log
192K	/var/cache
64K	/var/backups

View commands shown

These are the commands shown in the sanitized transcript.

Commands shown

df -h
du -sh /var/* 2>/dev/null | sort -h
du -sh /var/log /var/cache /var/backups 2>/dev/null

next steps

Related commands

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The disk was full, but guessing at folders was the slow part.

find /var -type f -printf '%s %p\n' | sort -nr | head -20

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Find Large Directories with du

Once you know a filesystem is full, the next question is where.

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

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A cleanup scan should not wander into mounted backups or network storage.

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

Hosting Operations Read-only

Check Inodes When Disk Space Looks Fine

Sometimes the disk has free bytes but still cannot create files.

df -ih