[olug] iso image
Brian Roberson
roberson at bstc.net
Wed Nov 7 04:43:31 UTC 2001
look at the key word here... mount... `man mount` and search for the word
"loop" or to save you the keystrokes....
####### `man 8 mount` #############
# ( search for keyword "loop".... e.g. type this after you are looking at
the man page: " /loop" and hit <enter> ( hopefully your $EDITOR is vi )
THE LOOP DEVICE
One further possible type is a mount via the loop device.
For example, the command
mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024
will set up the loop device /dev/loop3 to correspond to
the file /tmp/fdimage, and then mount this device on /mnt.
This type of mount knows about three options, namely loop,
offset and encryption, that are really options to los
etup(8). If no explicit loop device is mentioned (but
just an option `-o loop' is given), then mount will try to
find some unused loop device and use that. If you are not
so unwise as to make /etc/mtab a symbolic link to
/proc/mounts then any loop device allocated by mount will
be freed by umount. You can also free a loop device by
hand, using `losetup -d', see losetup(8).
######### `man 8 losetup` ##########
LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
NAME
losetup - set up and control loop devices
SYNOPSIS
losetup [ -e encryption ] [ -o offset ] loop_device file
losetup [ -d ] loop_device
DESCRIPTION
losetup 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 loop_device
argument is given, the status of the corresponding loop
device is shown.
OPTIONS
-d detach the file or device associated with the spec
ified loop device.
-e encryption
enable data encryption. The following keywords are
recognized:
NONE use no encryption (default).
XOR use a simple XOR encryption.
Blowfish
use Blowfish encryption. Blowfish encryption
is only available if you are using the
aux:~ # man losetup
LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
NAME
losetup - set up and control loop devices
SYNOPSIS
losetup [ -e encryption ] [ -o offset ] loop_device file
losetup [ -d ] loop_device
DESCRIPTION
losetup 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 loop_device
argument is given, the status of the corresponding loop
device is shown.
OPTIONS
-d detach the file or device associated with the spec
ified loop device.
-e encryption
enable data encryption. The following keywords are
recognized:
NONE use no encryption (default).
XOR use a simple XOR encryption.
Blowfish
use Blowfish encryption. Blowfish encryption
is only available if you are using the
international kernel and Blowfish encryption
has been enabled in the Crypto API.
Twofish
use Twofish encryption. Twofish encryption
is only available if you are using the
international kernel and Twofish encryption
has been enabled in the Crypto API.
CAST use CAST encryption. CAST encryption is only
available if you are using the international
kernel and CAST encryption has been enabled
in the Crypto API.
DES use DES encryption. DES encryption is only
available if the optional DES package has
been added to the kernel. DES encryption
uses an additional start value that is used
to protect passwords against dictionary
attacks. Use of DES is deprecated.
DFC use DFC encryption. DFC encryption is only
available if you are using the international
kernel and DFC encryption has been enabled
in the Crypto API.
IDEA use IDEA encryption. IDEA encryption is only
available if you are using the international
kernel and IDEA encryption has been enabled
in the Crypto API.
MARS use MARS encryption. MARS encryption is only
available if you are using the international
Linux Nov 24 1993 1
LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
kernel and MARS encryption has been enabled
in the Crypto API.
RC5 use RC5 encryption. RC5 encryption is only
available if you are using the international
kernel and RC5 encryption has been enabled
in the Crypto API.
RC6 use RC6 encryption. RC6 encryption is only
available if you are using the international
kernel and RC6 encryption has been enabled
in the Crypto API.
Serpent
use Serpent encryption. Serpent encryption
is only available if you are using the
international kernel and Serpent encryption
has been enabled in the Crypto API.
-o offset
the data start is moved offset bytes into the spec
ified file or device.
RETURN VALUE
losetup returns 0 on success, nonzero on failure. When
losetup displays the status of a loop device, it returns 1
if the device is not configured and 2 if an error occurred
which prevented losetup from determining the status of the
device.
FILES
/dev/loop0,/dev/loop1,... loop devices (major=7)
/proc/cipher/* available ciphers
EXAMPLE
If you are using the loadable module you must have the
module loaded first with the command
# insmod loop.o
The following commands can be used as an example of using
the loop device.
dd if=/dev/zero of=/file bs=1k count=100
losetup -e blowfish /dev/loop0 /file
Password :
mkfs -t ext2 /dev/loop0 100
mount -t ext2 /dev/loop0 /mnt
...
umount /dev/loop0
losetup -d /dev/loop0
If you are using the loadable module you may remove the
module with the command
# rmmod loop
Linux Nov 24 1993 2
LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
RESTRICTIONS
DES encryption is painfully slow. On the other hand, XOR
is terribly weak. Both are insecure nowadays. Some ciphers
require a licence for you to be allowed to use them.
BUGS
CAST, DES, RC5 and Twofish are currently broken and cannot
be used.
AUTHORS
Original version: Theodore Ts'o <tytso at athena.mit.edu>
Original DES by: Eric Young <eay at psych.psy.uq.oz.au>
----- Original Message -----
From: "Jazz Lover" <jzlvr at home.com>
To: <olug at bstc.net>
Sent: Tuesday, November 06, 2001 9:30 PM
Subject: Re: [olug] iso image
> What is a loop device?
>
>
>
> It is a byte image of a CDROM. You can burn it to CD or MOUNT it with a
> loop device to get its contents. Be careful to make the cd from the image
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