Permissions, flags and attributes
Change uid and gid
usermod -u 2005 foo
groupmod -g 3000 foo
find / -group 2000 -exec chgrp -h foo {} \;
find / -user 1005 -exec chown -h foo {} \;
usermod -g <NEWGID> <LOGIN>
End-to-end file access without read directory
chmod 711 <folder name>
Sticky Bit
chmod +t <folder or file name>