DUMMY Disks and Partitions

# ===== CHECK FREE SPACE ON MAIN DISK =====
sudo df -h /        # See available space on root filesystem

# ===== CREATE 1GB DUMMY DISK FILE =====
sudo fallocate -l 1G /tmp/disk1.img   # Create 1GB file to act as dummy disk

# ===== ATTACH FILE AS LOOP DEVICE (let system pick loop0) =====
sudo losetup -fP /tmp/disk1.img       # Map file to first free loop device (e.g., /dev/loop0)
losetup -a                             # Verify which loop device was assigned (likely /dev/loop0)
lsblk                                   # Confirm loop0 appears as a disk

# ===== CREATE PARTITIONS INSIDE LOOP0 (2 PARTITIONS EXAMPLE) =====
sudo fdisk /dev/loop0

Inside fdisk (for 2 partitions):

g       # Create new GPT partition table
n       # New partition
<Enter> # Default partition number 1
<Enter> # Default first sector
+512M   # Size 512MB
n       # New partition 2
<Enter> # Default partition number 2
<Enter> # Use remaining space (~512MB)
w       # Write changes and exit

Or for 3 partitions (~300MB each for first two):

g
n
<Enter>
<Enter>
+300M
n
<Enter>
<Enter>
+300M
n
<Enter>
<Enter>
<Enter>
w

# ===== INFORM KERNEL ABOUT PARTITIONS =====
sudo partprobe /dev/loop0        # Make kernel aware of new partitions
lsblk                             # Verify loop0p1 and loop0p2 appear

# ===== FORMAT AND MOUNT FIRST PARTITION =====
sudo mkfs.ext4 /dev/loop0p1       # Format first partition with ext4
sudo mkdir -p /mnt/test           # Create mount point
sudo mount /dev/loop0p1 /mnt/test # Mount partition
df -h                             # Verify mounted partition and space

# ===== DELETE SPECIFIC PARTITION =====
sudo fdisk /dev/loop0

Inside fdisk to delete partition 1:

d       # Delete partition
1       # Select partition 1
w       # Write changes

sudo partprobe /dev/loop0        # Inform kernel about partition change
lsblk                             # Verify partition removed

# ===== REMOVE ENTIRE DUMMY DISK =====
sudo umount /mnt/test             # Unmount any mounted partitions
sudo losetup -d /dev/loop0        # Detach loop device
sudo rm -f /tmp/disk1.img         # Delete the dummy disk file

# ===== VERIFY FREE SPACE ON MAIN DISK =====
lsblk
df -h /                           # Check free space on root filesystem