External USB Drives in Linux: Difference between revisions

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Adding external USB drives in Linux is easy. Etch uses hotplug to detect it. Using dmesg you can find out what mountpoint it is (Linux creates a SCSI device to mount to /dev/sdb and the drive will probably be /dev/sdb1).
Adding external USB drives in Linux is easy. Etch uses hotplug to detect it. Using dmesg you can find out what mountpoint it is (Linux creates a SCSI device to mount to /dev/sdb and the drive will probably be /dev/sdb1). NB you can't grep dmesg to find this, you have to look through it because the sd creation doesn't contain the word 'usb'.
 
/proc/bus/usb/devices shows you information about the connected USB device (you can tell what speed and type of usb device it is from here:
 
D: Ver= 2.00 Spd=480
 
C: MxPwr=  2mA
 
indicate it's USB 2)


/proc/bus/usb/devices shows you information about the connected USB device.


Most USB devices are formatted FAT32 which has a file size limit of 4GB. Because I'm using mine for Netvault backups and the virtual library media is created at sizes much larger than that, there are 2 choices:
Most USB devices are formatted FAT32 which has a file size limit of 4GB. Because I'm using mine for Netvault backups and the virtual library media is created at sizes much larger than that, there are 2 choices:
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(nb. it's better to use dd if=/dev/urandom of=/dev/sdb but takes much much longer...)
(nb. it's better to use dd if=/dev/urandom of=/dev/sdb but takes much much longer...)


In order to encrypt the whole disk I used this tutorial [http://www.hermann-uwe.de/blog/howto-disk-encryption-with-dm-crypt-luks-and-debian]
In order to encrypt the whole disk I used this tutorial [http://www.hermann-uwe.de/blog/howto-disk-encryption-with-dm-crypt-luks-and-debian]. There's another one here [http://www.saout.de/tikiwiki/tiki-index.php?page=EncryptedDeviceUsingLUKS].
 
Use dmesg and find usb to find out what device the kernel maps the drive to.


apt-get install cryptsetup hashalot
apt-get install cryptsetup hashalot

Latest revision as of 12:14, 16 October 2007

Adding external USB drives in Linux is easy. Etch uses hotplug to detect it. Using dmesg you can find out what mountpoint it is (Linux creates a SCSI device to mount to /dev/sdb and the drive will probably be /dev/sdb1). NB you can't grep dmesg to find this, you have to look through it because the sd creation doesn't contain the word 'usb'.

/proc/bus/usb/devices shows you information about the connected USB device (you can tell what speed and type of usb device it is from here:

D: Ver= 2.00 Spd=480

C: MxPwr= 2mA

indicate it's USB 2)


Most USB devices are formatted FAT32 which has a file size limit of 4GB. Because I'm using mine for Netvault backups and the virtual library media is created at sizes much larger than that, there are 2 choices:

ntfs-3G (which Etch doesn't support) and ext3 (which etch does).

Format to ext3 using

mke2fs -T ext3 /dev/sdb1

Then create an /etc/fstab entry

and mount


Test the (unmounted) disk for bad blocks and write garbage all over each block using

badblocks -c 10240 -s -w -t random -v /dev/sdb

(nb. it's better to use dd if=/dev/urandom of=/dev/sdb but takes much much longer...)

In order to encrypt the whole disk I used this tutorial [1]. There's another one here [2].

Use dmesg and find usb to find out what device the kernel maps the drive to.

apt-get install cryptsetup hashalot

cfdisk /dev/sdb (if you still need to partition the disk, unlikely though)

I like fdisk - the disk needs to be set up so that it has a partition on it, as the partitions are encrypted, not the entire disk! So create a primary partition at least...

cryptsetup --verbose --verify-passphrase luksFormat /dev/sdb1

Open the encrypted device and assign it to a virtual /dev/mapper/YOURNAME (TripTerra) device:

cryptsetup luksOpen /dev/sdb1 YOURNAME

mkfs.ext3 -m 1 -O dir_index,filetype,sparse_super /dev/mapper/YOURNAME


To mount

cryptsetup luksOpen /dev/sdb1 YOURNAME

mount /dev/mapper/TripTerra /mnt/


Now it's transparently encrypted


To unmount

umount /mnt/TripTerra

cryptsetup luksClose /dev/mapper/TripTerra