After some time of LXC usage SSH fails with `openpty: Permission denied`

[gozdal]

I'm running Ubuntu 14.04.2 LTS on GNU/Linux 3.13.0-45-generic x86_64 as a host machine for tests run on LXC guests.

After a few test runs on LXC machines, startup of next LXC machine hangs indefinitely.
At the same time SSH connections to the host machine display "PTY allocation request failed on channel 0" and SSH logs in auth.log

Feb 25 05:19:28 remotedev sshd[18578]: error: openpty: Permission denied
Feb 25 05:19:28 remotedev sshd[18628]: error: session_pty_req: session 0 alloc failed

Only reboot brings the machine back to usable state.
I've tried destroying the non-starting LXC guest, stopping removing all guests, purging lxc and lxc-templates.

[Serge Hallyn (serge-hallyn)]

Please show us the exact commands you used to create
and run the containers. Please show us the userids
you are running them as, and contents of /etc/subuid.

Please show /proc/slef/mountinfo both from the host
and a container.

 status: incomplete

[gozdal (gozdal)]

It seems that the problem was caused by autodev parameter that I added as per https://wiki.archlinux.org/index.php/Lxc-systemd. After removing extra options and using bare CentOS template the problem went away.

[Serge Hallyn (serge-hallyn)]

Interesting, thanks for the information.

[Arkadiy Kulev (eth-ethaniel)]

I am having exactly the same problem (I tried installing a openvpn server inside the LXC and needed to use autodev to setup TUN interface). My host machine failed shortly after:

cat > /usr/share/lxc/config/common.conf.d/02-openvpn-auto-tun.conf << EOL
lxc.hook.autodev = /usr/share/lxc/hooks/openvpn-auto-tun
EOL

cat > /usr/share/lxc/hooks/openvpn-auto-tun << EOL
#!/bin/bash
cd ${LXC_ROOTFS_MOUNT}/dev
mkdir net
mknod net/tun c 10 200
chmod 0666 net/tun
EOL

chmod 755 /usr/share/lxc/hooks/openvpn-auto-tun

[Arkadiy Kulev (eth-ethaniel)]

This is an old bug (2 years ago): http://lxc-users.linuxcontainers.narkive.com/QwhqLl5M/lxc-leaking-ptys

[Serge Hallyn (serge-hallyn)]

Did you say your *host* fails shortly after starting that container? In what way does the host fail?

Commenting out the line in 02-openvpn-auto-tun.conf avoids the problem?

[Arkadiy Kulev (eth-ethaniel)]

If you want to install openvpn inside LXC, here is how you do it cleanly without invoking autodev:
https://forum.proxmox.com/threads/tun-devices-in-ve-4-lxc.23473/#post-132952