Disk Management

Introduction

Monitoring disk space and managing storage drives is a critical task for any Linux administrator. Running out of disk space on a database server can cause catastrophic application crashes.

Checking Disk Space

The df Command

The df (Disk Free) command reports file system disk space usage. Always use the -h (human-readable) flag to print sizes in Megabytes (M) and Gigabytes (G) rather than blocks.

df -h

This will output a table showing the Filesystem, Size, Used, Avail, and Mounted on path for every drive connected to the machine.

The du Command

While df shows space for the entire drive, du (Disk Usage) estimates the space used by specific files or directories.

# Show the size of a specific directory in human-readable format
du -sh /var/log/

# Show the size of all subdirectories within the current folder
du -h --max-depth=1 .

Mounting and Unmounting Drives

Unlike Windows, where a new USB drive instantly appears as D:\, Linux requires you to "mount" physical drives to a specific folder in the existing file system tree.

1. Identify the Drive

Use the lsblk (List Block Devices) command to see all connected physical drives (e.g., /dev/sdb).

2. Mount the Drive

To access the files on /dev/sdb1, you must mount it to a directory.

# Create an empty directory
sudo mkdir /mnt/mydrive

# Mount the physical drive to the directory
sudo mount /dev/sdb1 /mnt/mydrive

Now, navigating to /mnt/mydrive will show the contents of the new disk!

3. Unmount the Drive

Before physically removing a drive, you must unmount it to prevent data corruption.

sudo umount /mnt/mydrive

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