#linux #user-management 

Change uid/gid of user
`usermod -u newnumber user`
`groupmod -g newnumber user`

File permissions in homedir will be automatically updated; file perms outside home dir will not be automatically updated.

Finding files of a specific user, and printing their uid/gid;
`sudo find / -user 4109 -printf '%p %u(%U) %g(%G)\n'`

To change only the group: `chgrp`.

Or using find to chmod/chgrp:
`sudo find / -user 4109 -group 4109 -exec chmod 998:998 {} \;`
`sudo find / -group 4109 -exec chgrp 998 {} \;`

Dirty way to find "system users" (uid < 999) - note that this is not fool-proof, it also lists groups
`getent passwd | grep -oP '\b[0-9]{3}\b' | uniq | sort`

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https://www.cyberciti.biz/faq/linux-change-user-group-uid-gid-for-all-owned-files/