I am trying to use recursive bind mount in a new user namespace and mount namespace.
This is what I do. Assume
/foo are both mount points.
Firstly I do
mount --rbind /foo/bar/ /baz, and then when I want to unmount it, I get
umount: /baz: device is busy.
I am sure that there is no other process is using
Then I tried to unmount
/baz/bar. This time I got
unmount: /baz/bar: not mounted.
However, I can see
What is going wrong or how should I bind mount and then unmount in a new user & mount namespace?