Comment 4 for bug 1940514

I read the source code of finalrd, when the system shutdown or reboot, it will copy the systemd-shutdown, /bin/sh and needed .so files, but I'm not sure when systemd switch to /run/initramfs/shutdown to finish shutdown.
I thought the error messages is from /run/initramfs/shutdown, it will umount /oldroot/dev/pts, but the device is busy.

I tried to umount /dev/pts before shutdown, the /oldroot/dev/pts is gone, but the /oldroot/dev is still there, there are too much devices node at /dev, I couldn't remove them to verify the error.