Change UID and GID of default user pi

Question

In my network environment I already have a user with the same UID (user id) and GID (group id) than the default user pi on Raspbian. This conflicts with user rights on my network, so I have to change these ids. How can I do this?

Answer 1

This is what I do.

Warning: Use at your own risk as making a mistake may require a reinstall.

1. log in as the pi user and add two more users with sudo adduser name1 and sudo adduser name2. The name2 user is a safeguard in case you make a mistake. Give both users the same password.
2. IMPORTANT. Now give the pi user the same password as used for the other two users. Use the passwd command to set the password.
3. Add both the new users to the sudo group. sudo adduser name1 sudo and sudo adduser name2 sudo.
4. Login as the new users in turn an check they can use sudo, e.g. sudo ls.
5. Login as name2.
6. Edit /etc/passwd and /etc/group. Swap all occurrences of pi to name1 and vice versa. Be careful.
7. Last step. Change the home directory ownerships. sudo chown pi.pi -R /home/pi and sudo chown name1.name1 -R /home/name1.

Answer 2

You can use usermod to change the user id UID and the group id GID of a user. But it is not all done with it. All files that are owned by the user has his id stored as metadata, so we have to scan all files and change its ids also. And there is another issue with the user pi on Raspbian. If you try to change his uid you get an error message that prevents changes:

rpi ~$ sudo usermod -u 65532 pi
usermod: user pi is currently used by process 608

And no, it doesn't help to kill all the processes owned by the user pi with sudo pkill -9 -u pi. At least one process is restarted immediately. It only helps to chroot into the not running filesystem of the SD Card and execute the commands. For this we need a second SD Card with Raspbian (Raspbian Light is sufficient) that you use to boot the RasPi. Then attach the original SD Card with your Card Reader to it. I assume it is attached as device /dev/sda. Now modify its filesystem as follows.

Chroot into the filesystem:

rpi ~$ sudo -Es
rpi ~# mkdir /mnt/p2
rpi ~# mount /dev/sda2 /mnt/p2
rpi ~# chroot /mnt/p2 /bin/bash

Change the ids and modify the files owned by user pi. It has uid and gid 1000. I will change them to 65532:

root@raspberrypi:/# usermod -u 65532 pi
root@raspberrypi:/# groupmod -g 65532 pi
root@raspberrypi:/# find / -group 1000 -exec chgrp -h pi {} \;
root@raspberrypi:/# find / -user 1000 -exec chown -h pi {} \;

Now check if its all correct:

root@raspberrypi:/# ls -aln /home/pi/
root@raspberrypi:/# id -u pi
root@raspberrypi:/# id -g pi
root@raspberrypi:/# grep pi /etc/passwd
root@raspberrypi:/# grep pi /etc/group
root@raspberrypi:/# find / -user pi -ls
root@raspberrypi:/# find / -group pi -ls

Clean up:

root@raspberrypi:/# exit
rpi ~# umount /mnt/p2
rpi ~# rmdir /mnt/p2
rpi ~# exit
rpi ~$

Boot the modified SD Card and use it. Most I have taken from How to Change a USER and GROUP ID on Linux For All Owned Files. Thanks to Vivek Gite. For more detailed information about the commands, look at his instructions.