I am no lxc expert, but there is a (fairly recent) suggested fix here[1]. I found this line in /etc/fstab in the container’s rootfs: devpts /dev/pts devpts nosuid,noexec,gid=tty,mode=620 0 0 After I added ptmxmode=666 to mount options, /dev/ptmx became 666.
Does that help? Mark [1] https://discuss.linuxcontainers.org/t/dev-ptmx-permission-issue/15509
