- find source and traget UID / GID using the id command on unix and dscllocalhostread/Local/Default/Users/lup in MacOsX
This post is certainly obsolete...
dscl . -change $HOME UniqueID 41167 545 dscl . -change $HOME PrimaryGroupID 41167 1007 chown -R 545:1007 $HOME
Remember to run the chown command afterwards, or you will not be able to access your home directory. Finally, log out and log in.
you may have to propagate changes on other drives (backup disks and such)