Comment 8 for bug 1642767

I'm running umask 027 (set in `.bashrc` for my user, which is copied to my root session after using `su`) and can report this issue still occurs for unprivileged containers under Debian 9 (stretch, stable) using LXC 2.0.7-2+deb9u2 and kernel 4.19.0-0.bpo.4-amd64. I can also confirm umask at container creation time does not matter. Another symptom of this issue is that after it occurred, `sync` (both the utility and system call) and `update-initramfs` (which calls `sync`) start hanging.

The comments to the [launchpad bug](https://discuss.linuxcontainers.org/t/cannot-stop-unprivileged-container-not-even-kill-9-its-systemd-process-on-host/1079) by the original author of this issue and [this](https://discuss.linuxcontainers.org/t/cannot-stop-unprivileged-container-not-even-kill-9-its-systemd-process-on-host/1079) thread contain a few discussions with regards to possible reasons this occurs. Also, is #2277 perhaps related?

It took a long time before I traced this down to the umask, because the symptoms are bewildering. My original issue:
https://superuser.com/questions/1439108/lxc-start-stop-hangs-and-filesystem-sync-hangs/1440273