bare systemd doesn't start anymore

[ghedo]

 % sudo build/pflask --chroot=$HOME/local/rootfs -- /lib/systemd/systemd 
[✘] Child was terminated by signal '9'

Weirdly enough, running it inside bash works fine:

 % sudo build/pflask --chroot=$HOME/local/rootfs -- bash
root@pinky:/# /lib/systemd/systemd --system
systemd 232 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN)
Detected virtualization container-other.
Failed to write /run/systemd/container, ignoring: No such file or directory
Detected architecture x86-64.

Welcome to Debian GNU/Linux 9 (stretch)!

Set hostname to <pinky>.
Couldn't move remaining userspace processes, ignoring: Input/output error
[  OK  ] Listening on /dev/initctl Compatibility Named Pipe.
[  OK  ] Listening on Journal Audit Socket.
[  OK  ] Listening on Journal Socket (/dev/log).
[  OK  ] Created slice System Slice.
[...]

I suspect this might have something to do with how we setup the pty.

Failed to write /run/systemd/container, ignoring: No such file or directory

systemd is likely unable to write to /run. I had the same error and what helped to solve was to make sure /run (and /run/lock) is a tmpfs and user that is running systemd is a root user (uid:gid 0:0).