usermod -u <NEWUID> <LOGIN>   
groupmod -g <NEWGID> <GROUP>
find / -user <OLDUID> -exec chown -h <NEWUID> {} \;
find / -group <OLDGID> -exec chgrp -h <NEWGID> {} \;
usermod -g <NEWGID> <LOGIN>

From <https://disqus.com/embed/comments/?base=default&disqus_version=c40f9aae&f=muffinresearchblog&t_u=https%3A%2F%2Fmuffinresearch.co.uk%2Flinux-changing-uids-and-gids-for-user%2F&t_d=Linux%3A%20Changing%20UIDs%20and%20GIDs%20for%20a%20user&t_t=Linux%3A%20Changing%20UIDs%20and%20GIDs%20for%20a%20user&s_o=default#2> 

Linux修改GID UID