I have been trying to figure this out for a few days. I have a
directory /var/peach/. I have a user user1 that reads and writes file1
to /var/peach. I have a user2 that reads and writes /var/peach/file1.
The only way that I can get them both to have access to newly created
files in /var/peach is by chown user1.user2 /var/peach

The problem is my user1's umask is set to 0022. I don't want to change
that at all. So how can i have it so that all files in /var/peach are
created as 770, without having the user chmod 770 /var/peach/file1
after he creates the file?

The only solution i have come up with is the posix acl. I'm using
resierfs (if that matters).

So how can I do this?