On Wed, Mar 8, 2017 at 2:56 AM, Prabhunath G [off-list ref] wrote:

Hi All,

         Binding / folder onto someother folder say /opt/lxc is not working
but otherway round is working. Can I get some help on this.

The following code snippet is executed after cloning
After executing the following code snippet the contents of / is visible in
/opt/lxc
      ret = mount("/", "/opt/lxc", NULL, MS_BIND, NULL);
      if (ret) {
        perror("mount bind / on /opt/lxc");
        exit(1);
     }

But after executing the following code snippet the contents of /opt/lxc is
not visible in /
      ret = mount("/opt/lxc", "/", NULL, MS_BIND, NULL);
      if (ret) {
        perror("mount bind /opt/lxc on /");
        exit(1);
     }

The code is executing successfully, but the result is not as expected.

It's a little curious that the bind succeeds -- if you try "mount
--move /opt/lxc /" you would get an error.  I'd guess there's some use
case for a / bind mount like that though offhand I don't see it.  But
bind mounts aren't substitutes for a chroot(2) call, which I think is
what you'll need for your application.  Bind mounts could still be
useful in setting up the running chroot environment: mount --bind
/proc /opt/lxc/proc, etc.


-- 
Jim