df Command Guide

Basic Usage

Running df without options shows disk usage for all mounted filesystems.

df

Output columns: Filesystem, 1K-blocks, Used, Available, Use%, Mounted on.

Common Options

Human-Readable Output

df -h

This is the most commonly used form, showing sizes in KB, MB, GB, etc.

Show Filesystem Type

df -hT

Adds a Type column showing ext4, xfs, tmpfs, etc.

Check Specific Filesystem

# Check specific path
df -h /home

# Check specific device
df -h /dev/sda1

Inode Usage

Inodes track files on the filesystem. You can run out of inodes even with free disk space if you have too many small files.

df -hi

Filtering Output

Show only specific filesystem type

# Show only ext4 filesystems
df -hT -t ext4

# Show only xfs filesystems
df -hT -t xfs

Exclude filesystem types

# Exclude tmpfs and devtmpfs
df -h -x tmpfs -x devtmpfs

Show local filesystems only

df -hl

Understanding the Output

Practical Examples

Quick disk space check

df -h /

Show total with all filesystems

df -h --total

Monitor disk usage in scripts

# Get usage percentage for root filesystem
df -h / | awk 'NR==2 {print $5}'

# Alert if usage exceeds 80%
usage=$(df -h / | awk 'NR==2 {print $5}' | tr -d '%')
if [ $usage -gt 80 ]; then
  echo "Warning: Disk usage is $usage%"
fi

Find filesystems with high usage

df -h | awk '$5 > 80 {print}'

Watch disk space in real-time

watch -n 5 df -h

Export to CSV format

df -h | awk 'BEGIN {OFS=","} {print $1,$2,$3,$4,$5,$6}'

Related Commands

Find large directories with du

# Find largest directories
du -h --max-depth=1 / 2>/dev/null | sort -hr | head -10

Summary

df is essential for monitoring disk space. Key takeaways:

• Use df -h for human-readable output
• Use df -hT to include filesystem type
• Use df -hi to check inode usage
• Use df -x tmpfs to exclude pseudo filesystems
• Combine with du to find what's using space