Why is my bind mount visible outside its mount namespace?

So I'm trying to get a handle on how Linux's mount namespace works. So, I did a little experiment and opened up two terminals and ran the following: Terminal 1 root@goliath:~# mkdir a b root@goliath:~# touch a/foo.txt root@goliath:~# unshare --mount -- /bin/bash root@goliath:~# mount --bind a b root@goliath:~# ls b foo.txt Terminal 2 root@goliath:~# ls b foo.txt How come the mount is visible in Te

[ngyuki]

util-linux 2.27 以降なら --make-private しなくても分離されていて、RHEL/CentOS 7.2 にはバックポートされている