Df

📂 Command: df (Disk Free)

The df command reports the amount of disk space used and available on your Linux filesystems. It’s your primary tool for making sure your partitions aren't hitting 100%.

1. The "Why"

On Arch Linux, you are the architect of your own system. Since you likely manage your own partitions (perhaps a separate /home or a specific EFI partition for rEFInd), you need to keep an eye on them.

• Prevent Crashes: If your root ( / ) partition hits 100%, your system might fail to boot or behave erratically.
• Monitor Backups: See how much space your Preader source code or e-book drafts are taking up on your drive.
• Check External Drives: Verify if a USB stick or external HDD is correctly mounted and how much room is left for your Android projects.

2. Basic Syntax

df [OPTIONS]

If you run just df, it will show sizes in 1-kilobyte blocks, which is very hard for humans to read. You will almost always use the "Human Readable" flag.

3. The "Must-Have" Flag: -h

The -h flag converts the output into Gigabytes (G) and Megabytes (M).

df -h

Understanding the Output Columns:

• Filesystem: The physical drive or partition (e.g., /dev/sda2).
• Size: Total capacity.
• Used: Space currently occupied.
• Avail: Space remaining.
• Use%: The percentage used (if this is over 90%, it's time to clean up!).
• Mounted on: Where the partition is attached to your folder structure.

4. Practical Examples

A. Checking a Specific Partition

If you only care about your home folder:

df -h /home

B. Checking Filesystem Types

If you want to see which partitions are ext4, fat32, or btrfs:

df -hT

C. Excluding "Temp" Filesystems

Linux uses many "virtual" filesystems in RAM (like tmpfs). To hide these and only see your actual hard drive partitions:

df -h --total -x tmpfs -x devtmpfs

5. Pro-Tips

• Inodes: Sometimes a disk says it has space, but you can't create new files. This usually means you've run out of "inodes" (index nodes). You can check this with df -i.
• Total Sum: Use df -h --total to see a grand total at the bottom of the list.
• Arch Linux Context: If you find your disk space disappearing unexpectedly, check your Pacman cache (/var/cache/pacman/pkg/). It stores every package you've ever downloaded. You can clean it with sudo paccache -r.

6. Summary Reference