is used to associate loop devices with regular files or block devices,
to detach loop devices and to query the status of a loop device. If only the
loopdev argument is given, the status of the corresponding loop
device is shown.
It is possible to specify transfer functions (for encryption/decryption
or other purposes) using one of the
There are two mechanisms to specify the desired encryption: by number
and by name. If an encryption is specified by number then one
has to make sure that the Linux kernel knows about the encryption with that
number, probably by patching the kernel. Standard numbers that are
always present are 0 (no encryption) and 1 (XOR encryption).
When the cryptoloop module is loaded (or compiled in), it uses number 18.
This cryptoloop module will take the name of an arbitrary encryption type
and find the module that knows how to perform that encryption.
show status of all loop devices
force loop driver to reread size of the file associated with the specified loop device
detach the file or device associated with the specified loop device(s)
-e, -E, --encryption encryption_type
enable data encryption with specified name or number
find the first unused loop device. If a
argument is present, use this device. Otherwise, print its name
-j, --associated file
show status of all loop devices associated with given
-k, --keybits num
set the number of bits to use in key to num.
Do not hash the password. By default, Debian systems run the password through a
hash function, non-Debian systems tend not to.
-o, --offset offset
the data start is moved offset bytes into the specified file or
the data end is set to no more than sizelimit bytes after the data start
-p, --pass-fd num
read the passphrase from file descriptor with number
instead of from the terminal
setup read-only loop device
print device name if the
option and a
argument are present.
The short form of this option (-s) is deprecated. This short form could
be in collision with Loop-AES implementation where the same option is used for
returns 0 on success, nonzero on failure. When
displays the status of a loop device, it returns 1 if the device
is not configured and 2 if an error occurred which prevented
from determining the status of the device.