Use losetup to virtualize a block device (File System)

Using losetup to virtualize Block devices (file systems) in Linux, SCSI disks support up to 15 partitions (3 primary partition sda1-sda3 + 1 Extension
Partition sda4 + 11 logical partition sda5-sda15), and The IDE disk only supports 63 partitions [root @ rhel6 ~] # Fdisk-l/dev/sda Disk/dev/sda: 6442 MB, 6442450944 bytes 16 heads, 63 sectors/track, 12483 cylinders Units = cylinders of 1008*512 = 516096 bytes Sector size (logical/physical): 512 bytes/512 bytes I/O size (minimum/optimal ): 512 bytes/512 bytes Disk identifier: 0x00053d18 Device Boot Start End Blocks Id System/dev/sda1 * 1 104 51200 83 Linux/dev/sda2 104 11076 5529600 8e Linux LVM/dev /Sda3 11076 12116 524288 82 Linux swap/Solaris/dev/sda4 12116 12483 185320 5 Extended/dev/sda5 12116 12136 10400 + 83 Linux/dev/sda6 12137 12157 10552 + 83 Linux/ dev/sda7 12158 12178 10552 + 83 Linux/dev/sda8 12179 12199 10552 + 83 Linux/dev/sda9 12200 12220 10552 + 83 Linux/dev/sda10 12221 12241 10552 + 83 Linux/ dev/sda11 12242 12262 10552 + 83 Linux/dev/sda12 12263 12283 10552 + 83 Linux/dev /Sda13 12284 12304 10552 + 83 Linux/dev/sda14 12305 12325 10552 + 83 Linux/dev/sda15 12326 12346 10552 + 83 Linux/dev/sda16 12347 12367 10552 + 83 Linux [root @ rhel6 ~] # Mkfs. ext4/dev/sda16 // although more than 15 partitions can be drawn, mke2fs 1.41.12 (17-May-2010) cannot be formatted) cocould not stat/dev/sda16 --- No such file or directory The device apparently does not exist; did you specify it correctly? [Root @ rhel6 ~] # Ls/dev/sda16 ls: cannot access/dev/sda16: No such file or directory loopback device can Virtualize files into block devices to simulate the entire file system, in this way, users can regard it as a hard drive, optical drive, and other devices, and mount it as a file system for use. As a result, the system can add more partitions (only loop0-loop7 by default) losetup-a displays the status of all used loopback devices-d disconnects loopback devices-f searches for the first unused loopback device-e <encryption Options> Start the encryption code [root @ rhel6 ~] # Losetup-f // find the first unused loopback device/dev/loop0 [root @ rhel6 ~] # Losetup-a // display the status of all used loopback devices [root @ rhel6 ~] # Dd if =/dev/zero of = loop. img bs = 10 M count = 10 10 + 0 records in 10 + 0 records out 104857600 bytes (105 MB) copied, 0.794912 s, 132 MB/s [root @ rhel6 ~] # Losetup-f loop. img // Virtualize loop. img into the first unused loop device [root @ rhel6 ~] # Losetup-a/dev/loop0: [fd00]: 26524 (/root/loop. img) [root @ rhel6 ~] # Losetup-f/dev/loop1 [root @ rhel6 ~] # Mkfs. ext4/dev/loop0 [root @ rhel6 ~] # Mount/dev/loop0/mnt/[root @ rhel6 ~] # Df-h Filesystem Size Used Avail Use % Mounted on/dev/mapper/Lrhel6-root 3.9G 2.4G 1.4G 64%/tmpfs 499 M 0 499 M 0%/dev/shm/dev/ sda1 49 M 27 M 20 M 59%/boot/dev/loop0 97 M 5.6 M 87 M 7%/mnt [root @ rhel6 ~] # Umount/mnt/[root @ rhel6 ~] # Losetup-d/dev/loop0 // The loop0 unmounts the loopback device.