Changing the UUID of a FAT32 or NTFS Partition

[Bouki]

i want change my usb disk uuid. but i dont understand the risk!
it means if i changed , it may not working?

[clubsoda]

i want change my usb disk uuid. but i dont understand the risk!
it means if i changed , it may not working?

Changing the UUID won't break the disk or make it unreadable. Some software might check UUIDs to try and detect unauthorised copying.

The risk I was referring to was the risk of making a mistake when running 'sudo dd' to read or write the superblock. That could definitely make the disk unreadable.

If it's that important, I suggest you backup the usb disk using gparted before changing the UUID. Please also read the dd manual page so you know what you're doing.

man dd

PS: To the thread moderator, my thanks.

[strudel]

Thank you! It worked perfectly for me on ubuntu 11.04
-strudel

[vkr]

I wrote a script to automate this process for NTFS partitions and to avoid overwriting anything that isn't NTFS (or at least reduce the risks). I'm sure one could modify it to work with FAT as well, but it's a starting point.

#!/bin/dash
IFS=""

# echo with exit for error termination
exho(){
    echo "error: $1"
    exit 1
}

# convert hexidecimal UUID to binary characters
uuid2bin(){
    STBF="$1"
    while [ -n "$STBF" ]; do
        BYTE="${STBF%??}"
        BYTE="${STBF#$BYTE}"
        STBF="${STBF%$BYTE}"
        BYTE="$(printf "%u\n" "0x$BYTE")"
        echo -n "$BYTE" | awk '{printf("%c",$0)}'
    done
    return 0
}

# usage help
if [ $# != 2 ]; then
    echo "$0 <UUID> <device>"
    exit 1
fi

# test the input UUID for validity
UUID_NEW="$(echo -n "$1" | tr [a-f] [A-F])"
STBF="${UUID_NEW#[0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F][0-9A-F]}"
if [ -n "$STBF" ]; then
    exho "invalid UUID format"
fi
if [ "$UUID_NEW" = 0000000000000000 ]; then
    exho "UUID cannot be empty"
fi

# get current/old UUID value via system tool
UUID_OLD="$(blkid -c /dev/null -s UUID -o value "$2" 2>/dev/null)"
if [ -z "$UUID_OLD" ]; then
    exho "could not read old UUID using blkid on $2"
fi

# get current/old UUID value via raw read
STBF="$(dd bs=1 skip=72 count=8 if="$2" 2>/dev/null | hexdump -ve '1/1  "%02X"')"
if [ ${#STBF} != 16 ]; then
    exho "could not read old UUID using dd on $2"
fi

# reorder the hex digits since they are reversed
UUID_RAW=""
while [ -n "$STBF" ]; do
    BYTE="${STBF%??}"
    BYTE="${STBF#$BYTE}"
    STBF="${STBF%$BYTE}"
    UUID_RAW="$UUID_RAW$BYTE"
done

# matching UUIDs confirm NTFS structure
if [ "X$UUID_RAW" != "X$UUID_OLD" ]; then
    exho "$2 invalid NTFS device"
fi

# write UUID to device
if ! uuid2bin "$UUID_NEW" | dd bs=1 seek=72 count=8 of="$2" 2>/dev/null && sync; then
    exho "could not write UUID to $2"
fi

# verify UUID
UUID_RAW="$(blkid -c /dev/null -s UUID -o value "$2" 2>/dev/null)"
if [ "X$UUID_RAW" != "X$UUID_NEW" ]; then
    exho "verification of new UUID failed"
fi

# status information
echo "DEVICE:\t\t$2"
echo "OLD UUID:\t$UUID_OLD"
echo "NEW UUID:\t$UUID_NEW"

[GMHilltop]

I have used this many times now and it works perfectly:
http://ubuntuforums.org/showpost.php...8&postcount=10

[wbloos]

This should patch the NTFS UUID with 8 random bytes (substitute the obvious with your actual NTFS partition designation, and all those spaces are required):

sudo dd if=/dev/urandom bs=80 count=1 | xxd -l 80 -c 8 | tail -1 | xxd -r - /dev/sd-NTFS-Partition

This works great. Thanks.