How to modify UUID

[kiyop]

You can modify UUID of partition as you like.

The UUID is written in the following place.

"EXT2, EXT3, EXT4"
16 bytes starting at 0x468=4*16^2+6*16+8=1128 bytes

"LINUX SWAP"
16 bytes starting at 0x40c bytes

"FAT16"
4 bytes starting at 0x27 (Little Endian)

"FAT32"
4 bytes starting at 0x43 (Little Endian)

"NTFS"
8 bytes starting at 0x48 (Little Endian)

"REISERFS"
16 bytes starting at 0x10054

"BTRFS"
(main)
16 bytes starting at 0x10020
(sub)
16 bytes starting at 0x1010b

===============
You can edit UUID of EXT3 partition (/dev/sda1) by the following method.

~$ sudo dd if=/dev/sda1 bs=1 count=16 skip=1128 > test
~$ hexedit test
Edit UUID as you like and save by pressing CTRL+X.
~$ sudo dd if=test bs=1 count=16 seek=1128 of=/dev/sda1

You must be wise enough to modify /etc/fstab and /etc/initramfs-tools/conf.d/resume et al. to boot correctly, if you changed the UUID of / partition and so on of Ubuntu.

EDIT at 2011/4/28 0:28 in JAPAN:
Windows may have information on UUID of partitions in registry.
http://ubuntuforums.org/showthread.php?t=480226&page=2

So it may be dangerous to change UUID of partition Windows uses.

[kiyop]

I wrote a script for changing UUID of a partition as you like.

It works on my ubuntu 10.10-desktop-jp.

Currently, it can deal only ext2,ext3,ext4,ntfs,reiserfs,fat16,fat32 and swap partition.


#!/bin/bash
echo "==============================================="
echo "UUID manipulater by Kiyoshi SUZUKI at 2011/4/20"
echo "==============================================="
gksu sleep 0
sudo blkid
echo "==============================================="
echo "Type the partition device file name the UUID of which you want to modify (for example, sda1)"
read a
if [ ! -e /dev/$a ];then
echo "/dev/$a does not exist. Abort!"
exit 0
fi
filesystem=$(sudo blkid /dev/$a|sed -e "s/.*TYPE=\"//" -e "s/\".*//")
echo "filesystem of /dev/$a is $filesystem"
littleendian () {
if [ $(expr $(echo $check1|wc -c) % 2) = 0 ];then
echo "number of word \"$check1\" is odd. Abort."
exit 0
else
repeatnum=$(expr $(expr $(echo $check1|wc -c) - 1) / 2 - 1)
len=$(expr $(echo $check1|wc -c) - 1)
while [ 0 -lt $repeatnum ];do
check1="$(echo $check1|cut -c3-$(expr $(expr $repeatnum \* 2) + 2))$(echo $check1|cut -c1-2)$(if [ $(expr $(expr $repeatnum + 1) \* 2) -lt $len ];then echo $check1|cut -c$(expr $(expr $repeatnum \* 2) + 3)-;fi)"
repeatnum=$(expr $repeatnum - 1)
done
fi
}
modify () {
sudo dd if=/dev/$a bs=1 count=$num skip=$skip > test 2>/dev/null
check1=$(hd test |head -n 1| sed -e "s/|.*//"|cut -c 9-|tr -d " ")
if [ $littleendian = "on" ];then littleendian;fi
check2=$(sudo blkid /dev/$a|tr -d "-"|sed -e "s/.*UUID=\"//" -e "s/\".*//")
echo $check1 : $check2 :
if [ $check1 = $(echo $check2|tr "[A-Z]" "[a-z]") ];then
echo "UUID is $check2"
echo "Please type what UUID you want to change to"
read newuuid
newuuid=$(echo "${newuuid}00000000000000000000000000000000"|cut -b1-$(expr $num + $num))
if [ $(echo $newuuid|tr -d "0123456789abcdef") ];then
echo "==============================================="
echo "UUID must consist of \"0123456789abcdef\" only. Abort."
echo "==============================================="
exit 0
fi
echo "==============================================="
echo "Do you want to change UUID of /dev/$a to ${newuuid} ? (Yes:y or No:other)"
read b
if [ $b = "y" ];then
if [ $littleendian = "on" ];then
check1=$newuuid
littleendian
newuuid=$check1
fi
echo "${newuuid}y"|hexedit test 2>/dev/null
check1=$(hd test|head -n 1| sed -e "s/|.*//"|cut -c 9-|tr -d " ")
if [ $littleendian = "on" ];then littleendian;fi
echo "==============================================="
echo "Please confirm new UUID of /dev/$a is:"
echo $check1
echo "Is it OK? (Yes:y, No:other)"
read ans
if [ $ans = "y" ];then
sudo dd if=test bs=1 count=$num of=/dev/$a seek=$skip 2>/dev/null && echo "UUID is modified. \"blkid\" command gives:
$(sudo blkid /dev/$a)
You should manually update (modify) system settings such as /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume and so on."
sudo sync
exit 0
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
else
echo "Something is wrong. Abort!"
exit 0
fi
}
case $filesystem in
ext2|ext3|ext4)
echo "Please type what UUID you want to change to"
read newuuid
newuuid=$(echo $newuuid|tr "[A-Z]" "[a-z]"|tr -d -- -)
newuuid=$(echo "${newuuid}00000000000000000000000000000000"|cut -b1-32)
if [ $(echo $newuuid|tr -d "0123456789abcdef") ];then
echo "==============================================="
echo "UUID must consist of \"0123456789abcdef\" only. Abort."
echo "==============================================="
exit 0
fi
echo "==============================================="
echo "Do you want to change UUID of /dev/$a to ${newuuid} ? (Yes:y or No:other)"
read b
if [ $b = "y" ];then
sudo tune2fs -U "$(echo $newuuid|cut -c1-8)-$(echo $newuuid|cut -c9-12)-$(echo $newuuid|cut -c13-16)-$(echo $newuuid|cut -c17-20)-$(echo $newuuid|cut -c21-32)" /dev/$a && echo "UUID is modified. \"blkid\" command gives:
$(sudo blkid /dev/$a)
You should manually update (modify) system settings such as /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume and so on."
sudo sync
exit 0
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
;;
swap)
num=16
skip=1036
littleendian="off"
modify
;;
ntfs)
num=8
skip=72
littleendian="on"
modify
;;
reiserfs)
num=16
skip=65620
littleendian="off"
modify
;;
btrfs)
num=16
skip=65568
littleendian="off"
modify
;;
vfat)
if [ -n "$(sudo blkid /dev/$a|grep msdos)" ];then
num=4
skip=39
littleendian="on"
modify
else
num=4
skip=67
littleendian="on"
modify
fi
;;
*)
echo "Filesystem type $filesystem is not supported. Abort."
exit 0
;;
esac
exit 0

save it as "UUIDmanipulater.sh".
And execute in terminal, for example,
bash UUIDmanipulater.sh

* Known problems *

UUID of swap partition did not changed by this script sometimes.

[Artemis3]

Great, So now you can now label your stuff...

deadbeef-cafe-babe-feed-defacefacade or something ;)

[kiyop]

Yes!:guitar:

We can use:

face
babe
bad
dad
ace
aced
cab
cafe
baba
aba
abaca
abbe
abd
abed
baa
bade
fade
ba11
ab1e-b0d1ed;)

et al.

I want to make a sentence.:P

By the way,
I want to include some function to search former UUID value in /etc/fstab and/or /boot/grub/grub.cfg or /boot/grub/menu.lst and/or /etc/initramfs-tools/conf.d/resume,
and to help changing them into my script.

***
The reason I tried to change UUID is that I sometimes need to type kernel option such as "root=UUID=..." and it is difficult to remember and type UUID value correctly.
I changed UUID of partitions like,
100000000000...
1234567890abcdef...

Of course, now I know that I can write like "root=LABEL=...", which is easier for me to remember. I can modify label of partition easily.

[kiyop]

I added the function to search old UUID value from /etc/fstab, /boot/grub/grub.cfg, /boot/grub/menu.lst, and /etc/initramfs-tools/conf.d/resume and give chance to change the old UUID value to the new one.

Edit: I fixed a bug at 2011/4/26 12:06 in Japan

The script is as follows:

#!/bin/bash
echo "==============================================="
echo "UUID manipulater by Kiyoshi SUZUKI at 2011/4/25"
echo "==============================================="
gksu sleep 0
sudo blkid
echo "==============================================="
echo "Type the partition device file name the UUID of which you want to modify (for example, sda1)"
read a
if [ ! -e /dev/$a ];then
echo "/dev/$a does not exist. Abort!"
exit 0
fi
filesystem=$(sudo blkid /dev/$a|sed -e "s/.*TYPE=\"//" -e "s/\".*//")
echo "filesystem of /dev/$a is $filesystem"
littleendian () {
if [ $(expr $(echo $check1|wc -c) % 2) = 0 ];then
echo "number of word \"$check1\" is odd. Abort."
exit 0
else
repeatnum=$(expr $(expr $(echo $check1|wc -c) - 1) / 2 - 1)
len=$(expr $(echo $check1|wc -c) - 1)
while [ 0 -lt $repeatnum ];do
check1="$(echo $check1|cut -c3-$(expr $(expr $repeatnum \* 2) + 2))$(echo $check1|cut -c1-2)$(if [ $(expr $(expr $repeatnum + 1) \* 2) -lt $len ];then echo $check1|cut -c$(expr $(expr $repeatnum \* 2) + 3)-;fi)"
repeatnum=$(expr $repeatnum - 1)
done
fi
}
modify () {
sudo dd if=/dev/$a bs=1 count=$num skip=$skip > test 2>/dev/null
check1=$(hd test |head -n 1| sed -e "s/|.*//"|cut -c 9-|tr -d " ")
if [ $littleendian = "on" ];then littleendian;fi
check2=$(sudo blkid /dev/$a|tr -d "-"|sed -e "s/.*UUID=\"//" -e "s/\".*//")
if [ $check1 = $(echo $check2|tr "[A-Z]" "[a-z]") ];then
olduuid=$(sudo blkid /dev/$a|sed -e "s/.*UUID=\"//" -e "s/\".*//")
echo "UUID is $olduuid"
echo "Please type what UUID you want to change to"
read newuuid
newuuid=$(echo "${newuuid}00000000000000000000000000000000"|cut -b1-$(expr $num + $num))
if [ $(echo $newuuid|tr -d "0123456789abcdef") ];then
echo "==============================================="
echo "UUID must consist of \"0123456789abcdef\" only. Abort."
echo "==============================================="
exit 0
fi
echo "==============================================="
echo "Do you want to change UUID of /dev/$a to ${newuuid} ? (Yes:y or No:other)"
read b
if [ $b = "y" ];then
check1=$newuuid
if [ $littleendian = "on" ];then
littleendian
fi
echo "${check1}y"|hexedit test 2>/dev/null
check1=$(hd test|head -n 1| sed -e "s/|.*//"|cut -c 9-|tr -d " ")
if [ $littleendian = "on" ];then littleendian;fi
echo "==============================================="
echo "Please confirm new UUID of /dev/$a is:"
echo $check1
echo "Is it OK? (Yes:y, No:other)"
read ans
if [ $ans = "y" ];then
sudo dd if=test bs=1 count=$num of=/dev/$a seek=$skip 2>/dev/null && echo "UUID is modified. \"blkid\" command gives:
$(sudo blkid /dev/$a)
You should manually update (modify) system settings such as /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume and so on.
I will check /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume for $olduuid."
sudo sync
newuuid=$(echo $check1|cut -c1-$(echo $cutspace|cut -d " " -f1))
loc1=$(echo $cutspace|cut -d " " -f1)
cutspace=$(echo "$cutspace"|cut -d " " -f2-)
for loc2 in $cutspace;do
newuuid=$newuuid$(echo -$(echo $check1|cut -c$(expr $loc1 + 1)-$loc2))
loc1=$loc2
done
changefstabetal
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
else
echo "Something is wrong. Abort!"
exit 0
fi
}
modifyfile () {
if [ -e /mnt$file ];then
if [ "$(grep $olduuid /mnt/$file|grep -v ^#)" ];then
for line in $(grep -n $olduuid /mnt$file|grep -v ^[0-9]*:#|tr " " "_");do
answer="1"
while :;do
echo "There is the following line in $file in /dev/$aa:"
echo $(echo $line|sed -e "s/^[0-9]*:/& lines:/")
echo "Do you change \"$olduuid\" to \"$newuuid\" ?(yes=y,no=n)"
read answer
if [ "$answer" = "y" ];then
perm=$(ls -l /mnt$file|cut -c2-10)
perm2=$(expr 0 $(echo $perm|cut -c1-3|sed -e "s/r/ + 4/" -e "s/w/ + 2/" -e "s/x/ + 1/" -e "s/-//g"))$(expr 0 $(echo $perm|cut -c4-6|sed -e "s/r/ + 4/" -e "s/w/ + 2/" -e "s/x/ + 1/" -e "s/-//g"))$(expr 0 $(echo $perm|cut -c7-9|sed -e "s/r/ + 4/" -e "s/w/ + 2/" -e "s/x/ + 1/" -e "s/-//g"))
sudo mv -f /mnt$file /mnt${file}.backup
sudo touch /mnt$file
sudo chmod a+w /mnt$file
cat /mnt${file}.backup|sed "$(echo $line|cut -d: -f1)s/$olduuid/$newuuid/" > /mnt$file
sudo chmod $perm2 /mnt$file
break
elif [ "$answer" = "n" ];then break
fi
done
done
fi
fi
}
changefstabetal () {
deviceslist=$(sudo blkid|cut -d: -f1)
for aa in $deviceslist;do
sudo umount -l /mnt 2>/dev/null
sudo mount -t $(sudo blkid $aa|sed -e "s/.*TYPE=\"//"|sed -e "s/\".*//") $aa /mnt 2>/dev/null || continue
echo "checking $aa"
file="/etc/fstab"
modifyfile
file="/boot/grub/grub.cfg"
modifyfile
file="/boot/grub/menu.lst"
modifyfile
file="/etc/initramfs-tools/conf.d/resume"
modifyfile
umount -l /mnt 2>/dev/null
done
}
case $filesystem in
ext2|ext3|ext4)
olduuid=$(sudo blkid /dev/$a|sed -e "s/.*UUID=\"//" -e "s/\".*//")
echo "UUID is $olduuid"
echo "Please type what UUID you want to change to"
read newuuid
newuuid=$(echo $newuuid|tr "[A-Z]" "[a-z]"|tr -d -- -)
newuuid=$(echo "${newuuid}00000000000000000000000000000000"|cut -b1-32)
if [ $(echo $newuuid|tr -d "0123456789abcdef") ];then
echo "==============================================="
echo "UUID must consist of \"0123456789abcdef\" only. Abort."
echo "==============================================="
exit 0
fi
newuuid="$(echo $newuuid|cut -c1-8)-$(echo $newuuid|cut -c9-12)-$(echo $newuuid|cut -c13-16)-$(echo $newuuid|cut -c17-20)-$(echo $newuuid|cut -c21-32)"
echo "==============================================="
echo "Do you want to change UUID of /dev/$a to ${newuuid} ? (Yes:y or No:other)"
read b
if [ $b = "y" ];then
sudo tune2fs -U $newuuid /dev/$a && echo "UUID is modified. \"blkid\" command gives:
$(sudo blkid /dev/$a)
You should manually update (modify) system settings such as /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume and so on.
I will check /etc/fstab, /boot/grub/grub.cfg, /etc/initramfs-tools/conf.d/resume."
sudo sync
changefstabetal
exit 0
else
echo "If you want to change, type \"y\". Abort."
exit 0
fi
;;
swap)
num=16
skip=1036
littleendian="off"
cutspace="8 12 16 20 32"
modify
;;
ntfs)
num=8
skip=72
littleendian="on"
cutspace="16 "
modify
;;
reiserfs)
num=16
skip=65620
littleendian="off"
cutspace="8 12 16 20 32"
modify
;;
btrfs)
num=16
skip=65568
littleendian="off"
cutspace="8 12 16 20 32"
modify
;;
vfat)
littleendian="on"
cutspace="4 8"
if [ -n "$(sudo blkid /dev/$a|grep msdos)" ];then
num=4
skip=39
else
num=4
skip=67
fi
modify
;;
*)
echo "Filesystem type $filesystem is not supported. Abort."
exit 0
;;
esac
exit 0

[kiyop]

Sometimes, the odd word "" which means CTRL+x is eliminated after submission.

echo "${check1}y"|hexedit test 2>/dev/nullEdit at 2011/4/26 12:11 in Japan:
I cannot correctly submit "" which means CTRL+x in this forum.
I submitted the correct script at
http://kiyoandkei.blog68.fc2.com/blog-entry-51.html

EDIT at 2011/4/28 0:35 in JAPAN
A recent one is
http://blog-imgs-17.fc2.com/k/i/y/kiyoandkei/UUIDmanipulater110427no1.txt (http://blog-imgs-17.fc2.com/k/i/y/kiyoandkei/UUIDmanipulater110426no1.txt)

[kiyop]

I am not sure, but Windows may have information on UUID of partitions in registry.
http://ubuntuforums.org/showthread.php?t=480226&page=2

So it may be dangerous to change UUID of partition Windows uses.

I will write this in #1