Create and mount a loopback filesystem

loopback_filesystem.sh

#!/usr/bin/env bash

## Loopback Filesystem
# This script will create and mount a loopback filesystem
# Useful if you need to limit director(ies) by size
# but only have one volume
# This script needs to be run with sudo

LO_FILESYSTEM_NAME=my_loopback
LO_FILESYSTEM_MB_SIZE=5
MOUNT_LOCATION="/backup"

# Check if we have proper permissions
if [ "$EUID" -ne 0 ]; then
  echo "Please run as root/with sudo"
  exit
fi

# Check if $MOUNT_LOCATION already exists
if [ -d "$MOUNT_LOCATION" ]; then
  echo "Directory $MOUNT_LOCATION already exists. Please clean up and run again."
  exit
fi


# Create a file that is the size you want your filesystem to be
# Size = bs*count
# You CAN change the block size (bs) to be bigger, and then lower your count
# but that will create performance problems for anything that is comparing blocks
LO_FILESYSTEM_SIZE=$((LO_FILESYSTEM_MB_SIZE*10000))
echo "Creating file..."
dd if=/dev/zero of=$LO_FILESYSTEM_NAME bs=1024 count=$LO_FILESYSTEM_SIZE &> /dev/null

# Check to see which loop device we can use
for LOOP_DEVICE in {0..7}; do
  losetup /dev/loop$LOOP_DEVICE &> /dev/null
  if [ $? -eq 1 ]; then
    break
  fi
done

# Attach file as loopback device
echo "Using /dev/loop$LOOP_DEVICE"
losetup /dev/loop$LOOP_DEVICE $LO_FILESYSTEM_NAME &> /dev/null

# Add a filesystem to our new device
echo "Adding filesystem to /dev/loop$LOOP_DEVICE"
mkfs -t ext4 /dev/loop$LOOP_DEVICE &> /dev/null

# Mount the filesystem
echo "Mounting at $MOUNT_LOCATION"
mkdir -p $MOUNT_LOCATION
mount -t ext4 /dev/loop$LOOP_DEVICE $MOUNT_LOCATION

# Add entry to /etc/fstab
echo "/dev/loop$LOOP_DEVICE	$MOUNT_LOCATION	ext4	defaults	0 0" >> /etc/fstab



#dd if=/dev/zero of="$image" bs=1024K count="$img_size"
#mkfs.xfs "$image"
#sudo mount -o loop "$image" "$mount_path"
#sudo chown $USER:$USER "$mount_path"