Linux

df & du — Check Disk Usage

Use df to see filesystem-level disk space and du to find which files and directories are consuming the most space.

March 21, 20255 min read

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df — Disk Free (Filesystem Level)

df reports available and used disk space for each mounted filesystem.

df                             # All filesystems
df -h                          # Human-readable (KB/MB/GB)
df -h /                        # Root filesystem only
df -h /home                    # Specific mount point
df -T                          # Show filesystem type
df -i                          # Inode usage instead of blocks

Reading df Output

# Example output:
# Filesystem      Size  Used Avail Use% Mounted on
# /dev/sda1        50G   20G   28G  42% /
# tmpfs            16G     0   16G   0% /dev/shm
# /dev/sda2       200G  150G   40G  79% /home

# 79% usage on /home — getting full! Time to clean up.

du — Disk Usage (Directory Level)

du measures how much space files and directories consume. Great for finding what's eating your disk.

du -sh /home/sagar              # Total size of a directory
du -sh *                        # Size of each item in current dir
du -sh */ | sort -h             # Directories sorted by size (asc)
du -h --max-depth=1 /home       # One level deep only
du -ah /var/log | sort -rh | head -10   # Top 10 largest items

# Find top space consumers at root
du -h --max-depth=1 / 2>/dev/null | sort -rh | head -10

du Options

Option	Description
`-s`	Summary (total only, no subdirs)
`-h`	Human-readable sizes
`--max-depth=N`	Limit recursion depth
`-a`	Include files (not just dirs)
`-c`	Show grand total at end

Find Large Files

# Find files over 100MB
find / -type f -size +100M 2>/dev/null | head -20

# Find top 5 space users in /var
du -sh /var/* | sort -rh | head -5

# Check if disk is nearly full (>85%)
df -h / | awk 'NR==2 {print $5}'

Run du -sh */ | sort -rh from a directory to instantly see which subdirectory is largest — great for tracking down disk hogs.

Quick Check

Which command shows the total size of a single directory?

Exercise

Check how full your root filesystem is with df. Then find which directory in /var uses the most space.