Creating loop device on fedora

We can create a loop device in Linux which we can use as a virtual device for experiment. Following steps will show how to create loop device and use it for creation of file system. 

• Add new device

 # losetup -f

/dev/loop0

• Create a file which will serve as virtual device.

# dd if=/dev/urandom of=/bhushan bs=1M count=128

128+0 records in
128+0 records out
134217728 bytes (134 MB, 128 MiB) copied, 12.9207 s, 10.4 MB/s

• Setup up the mapping between loop device and new file 

# losetup /dev/loop0 /bhushan

• Use new virtual device for file system creation

# mkfs -t ext4 /dev/loop0
mke2fs 1.43.3 (04-Sep-2016)
Discarding device blocks: done                          
Creating filesystem with 131072 1k blocks and 32768 inodes
Filesystem UUID: 7be2cbaf-a2a5-4319-a7e9-51b749c69184
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729

Allocating group tables: done                          
Writing inode tables: done                          
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

# mount -t ext4 /dev/loop0 /mnt

# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/loop0               120M  1.6M  110M   2% /mnt1

# umount /mnt1

• Detach a file from loop device

# losetup -d /dev/loop0