losetup(loop setup)
losetup(loop setup)功能说明：设置循环设备。
语 法：losetup [-d][-e <加密方式>][-o <平移数目>][循环设备代号][文件]
补充说明：循环设备可把文件虚拟成区块设备，籍以模拟整个文件系统，让用户得以将其视为硬盘驱动器，光驱或软驱等设备，并挂入当作目录来使用。
参 数：
-d 卸除设备。
-e<加密方式> 启动加密编码。
-o<平移数目> 设置数据平移的数目。
losetup
losetup [options] loopdevice [file]
System administration command. Set up and control loop devices. Attach a loop device to a regular file or block device, detach a loop device, or query a loop device. A loop device can be used to mount an image file as if it were a normal device.
Options
Detach specified loopdevice.
Use specified kernel encryption module when performing writes and reads. (Usually NONE, DES, and XOR.) You may also specify the encryption module by number. When using DES encryption, you will be prompted for an initialization passphrase.
Start reading data at offset bytes from the beginning of file.
Read the passphrase from file descriptor fd.