How to Change a USER and GROUP ID on Linux For All Owned Files

I

would like to know how to change a UID (USER ID)/GID (GROUP ID) and all belonging files on Linux operating system. Say, I want to change UID from 1005 to 2005 and GID from 1005 to 2005 on Linux. How do I make such change for belonging files and directories?

 

The procedure is pretty simple:

First, assign a new UID to user using the usermod command.

Second, assign a new GID to group using the groupmod command.

Finally, use the chown and chgrp commands to change old UID and GID respectively. You can automate this with the help of find command.

It cannot be stressed enough how important it is to make a backup of your system before you do this. Make a backup. Let us say:

Our sample user name: foo

Foo’s old UID: 1005

Foo’s new UID: 2005

Our sample group name: foo

Foo’s old GID: 2000

Foo’s new GID: 3000

Commands

To assign a new UID to user called foo, enter:

# usermod -u 2005 foo

 

To assign a new GID to group called foo, enter:

# groupmod -g 3000 foo

 

Please note that all files which are located in the user’s home directory will have the file UID changed automatically as soon as you type above two command. However, files outside user’s home directory need to be changed manually. To manually change files with old GID and UID respectively, enter:

# find / -group 2000 -exec chgrp -h foo {} \;

# find / -user 1005 -exec chown -h foo {} \;

 

The -exec command executes chgrp or chmod command on each file. The -h option passed to the chgrp/chmod command affect each symbolic link instead of any referenced file. Use the following command to verify the same:

# ls -l /home/foo/

# id -u foo

# id -g foo

# grep foo /etc/passwd

# grep foo /etc/group