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There is only one user on my system. How can I change its user ID from the default of 1000?

If there are additional steps that would be required in order to avoid breaking the login process on a typical desktop installation, those should be included as part of the answer.

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4  
Out of curiosity, what are the reasons for changing a user ID? –  Olivier Lalonde Dec 9 '10 at 2:27
8  
If you commonly exchange data with other systems via NFS, or just some copy method which preserves the UID, it will help if you use the same UID for the same username across systems. –  João Pinto Dec 9 '10 at 11:16
    
João got it right. In particular, I'm hoping to match up UIDs with users in Mac OS X so that a shared filesystem carries the intended permissions across operating systems. –  ændrük Dec 9 '10 at 16:16

7 Answers 7

up vote 14 down vote accepted

The problem is that, like you mentionned, you cannot change your user's UID when it is logged in a session. You have to use another user account to proceed.

But you don't have to create a new user account, promote it to admin, log out, log in to the new amdin account, change your primary account's UID, log out, log in to your primary account then delete the new admin user just change your UID. ;)

You can boot into recovery mode (it's an option that appears when you start up your computer). This will log you in a root session. Being logged in root -- and not your usual user account --, you will be able to modify your UID.

Because the recovery mode only works in command line interface, once logged into a root session, you will have to use Luis Alvarado's command: usermod -u NEW_UID your_username. Follow ddeimeke's instructions to update file permissions. Then, reboot your computer (reboot), so you can boot in normal mode.

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1  
Doesn't work for Ubuntu 14.04. After doing usermod -u NEW_UID your_username and find / -uid 1000 -exec chown -h 5000 '{}' \+, reboot leads to a guess-session-only GUI login. –  Kay Apr 28 at 7:19
    
Maybe, hidden files in the home are not changed properly? Do you use encryption for your home? –  math Jun 18 at 7:53

You can change it in /etc/passwd, /etc/group and /etc/shadow or you use one of the preferred possibilties above. But - most important - you have to change the ownership of all files belonging to the user.

For instance, if the old user id is 1000 and the new one is 5000:

find / -uid 1000 -exec chown -h 5000 '{}' \+

And the same for the group id (if you change it as well).

find / -gid 1000 -exec chgrp -h 5000 '{}' \+
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7  
This is a really important point. Many things will break if you follow the techniques given in the other answers without also doing this. –  poolie Dec 9 '10 at 6:41
3  
I just learnt one should better use sudo find / -xdev -uid 1000 -exec chown 5000 '{}' \+, otherwise one would include mounted data (in /mnt, which is possibly undesired) and files you better not mess with in /proc and /dev. See this post –  Sebastian Jan 12 '12 at 16:42
    
This is not a good idea. Given the case that /home is on a different filesystem, you will not even change the ownership of your own files. –  ddeimeke Jan 13 '12 at 8:37
    
On this answer you should change the group and uid permissions, before editing the files in /etc, right? –  MrDaniel Mar 27 '12 at 19:49
    
It does not matter, what you do first. –  ddeimeke Mar 28 '12 at 9:06

Complete solution based on @AlexandreP. and @ddeimeke + official documentation. No reboot necessary.

The Debian/Ubuntu policy is that if there is a user jim with user ID 1001, there is also a group jim with group ID 1001. This solution also updates those group IDs.

  1. Enable the root account:

    sudo passwd root
    
  2. If the user is logged in, then log out (also on virtual terminals)
  3. Go to VT1: Ctrl-Alt-F1
  4. Log in as root and run this with the user name and old/new UID supplied:

    # put the information we need in variables
    username=...
    old_uid=`id -u $username`  # looks up current (old) uid
    new_uid=...
    
    # update the user ID and group ID for $username
    usermod -u $new_uid $username
    groupmod -g $new_uid $username
    
    # update the file ownerships
    # NB: you cannot combine the next two chowns, or files where 
    # only the uid xor the gid matches won't be updated  
    chown -Rhc --from=$old_uid $new_uid /    # change the user IDs
    chown -Rhc --from=:$old_uid :$new_uid /  # change the group IDs
    
  5. Log out
  6. Log in as $username
  7. Disable the root account:

    sudo passwd -dl root
    
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Enabling the root account shouldn't be necessary; just use Recovery Mode. –  ændrük Jul 24 '12 at 13:56
2  
This should be faster than rebooting, which is why I posted it. –  l0b0 Jul 24 '12 at 18:25
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In Ubuntu 14.04 and 14.10 you also need to fix the extended ACL permissions in /media otherwise automounting (in Nautilus/Nemo) breaks as the old UID remains. sudo setfacl -m "u:<NEWUID>:r-x" /media/<USERNAME> sudo setfacl -x "u:<OLDUID>" /media/<USERNAME> –  richud.com Nov 7 at 19:29

If you go to console and type: usermod --help you will get one of the parameters saying:

-u, --uid UID new UID for the user account

so if you want to change the UID for user cyrex then do:

usermod -u 1000 cyrex

that would change the uid for cyrex from whatever value it had before to 1000

If you want to do it visually then do this:

Go to

SYSTEM --> ADMINISTRATION --> USERS AND GROUPS

Select yourself from the list and click on ADVANCED SETTINGS

UID is at the end of that window.

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1  
I tried the graphical method you suggested, but there is a message saying "You can't change user ID while the user is logged in." Have you tested this method? –  ændrük Dec 9 '10 at 23:13
1  
Hehe well that is true. I tried with another account. You need to login via root or any other admin account. Then do the graphical way. Sorry for that. –  Luis Alvarado Dec 10 '10 at 13:19
  • Goto System>>Administration>>Users and Groups

alt text

  • Click Advanced Settings and goto Advanced Tab there in the bottom you will see your user id.
  • Change it and click ok.
    alt text
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1  
Should I just ignore the warning in your screenshot, "You can't change user ID while the user is logged in."? –  ændrük Dec 9 '10 at 16:20
    
You have to change it from another another user account to get rid of this warning. –  karthick87 Dec 9 '10 at 16:42
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My question is "How can I change my own user ID?". If you intend your answer to be that I should create a new user just to edit this value, you should edit your answer to indicate so. –  ændrük Dec 9 '10 at 23:10

With KDE: In the Change Advanced User Settings Menu:

Changing from another user does not work for 1000 which is the default user.

you have to do that manually - my experience

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First you need to login as root, at least for a while, so let us make this possible:

sudo passwd root

Reboot, ctrl + alt + f1 to switch to the console, login as root, do the following (ownership in home dir will be taken care of automatically):

groupmod --gid NEWGID username
usermod  --uid NEWUID username 

For your files in places other than your home dir, to this:

sudo chown -R username:username /path/to/files

Delete and lock the passwd of root, if you want. (I tend to keep it):

passwd -dl root
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