What does `chmod u+s directory` do?
chmod g+s directory makes new files inherit the group of the directory. I thought that chmod u+s directory would make them inherit the directory owner, but they don't and I see no other effect.
Solution 1:
Nothing useful, generally.
According to Sven Mascheck's page on special permission bits, the u+s bit only has an effect on three non-Linux operating systems:
on HP-UX up to 9, marks the file as context-dependent (pages 607, 828)
on FreeBSD, if built with the kernel option, allows user ownership to be inherited like
g+s;on SCO OpenServer, enables file versioning.