[lxc-users] lxc-attach runs in root fs, not container chroot

[Noel Burton-Krahn]

Hi,

I'm running lxc-1.0.6-r1 on Gentoo.  I can create my lxc container and ssh
into it and everything looks fine.

lxc-create -n u1 -t download -- --no-validate --dist ubuntu --release
trusty --arch amd64

lxc-start -n u1


However, lxc-attach runs programs in the host's root, not in the container
root:

lxc-attach -n u1 ls /tmp

This lists files in the *hosts* /tmp.  The guest's /tmp is empty

Looking at /proc/$PID/mountinfo in host and guest, I see that processes
created inside the guest are chrooted to the right place:

(in lxc guest, init is chrooted)

head -1 /proc/1/mountinfo
81 124 0:2 /etc/lxc/u1/rootfs / rw - rootfs rootfs
rw,size=16332604k,nr_inodes=4083151

However, programs run by lxc-attach are not chrooted

lxc-attach -n u1 -- head -1 /proc/self/mountinfo
82 82 0:2 / / rw - rootfs rootfs rw,size=16332604k,nr_inodes=4083151


What config options could break this?

I created a small program that just does nsexec [1], and it has the same
behaviour.  somehow, setns() is not setting the root fs properly using
processes running in lxc.


[1] https://gist.github.com/noelbk/b6964f8c55d5f6258819


PS
This all works fine on stock ubuntu-14.04/

Cheers,
--
Noel
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