Why did the /run/php directory stop being created after a reboot?

Question

linux

Debian 10 OS.
Haven't rebooted the server for about a month. Reloaded today.
php-fpm stopped working. Digging through the logs, I realized that he could not create a directory for himself in /run/.

I do:
mkdir /run/php && systemctl reststart php7.3-fpm
Everything starts. But since the system deletes everything in /run on reboot, the php directory is not created after the reboot.

At the same time, I did not change anything in the configs for a long time. After the kernel updates rebooted the server, everything started.
The only thing I sin on is updates during the last month. But on the other hand, this is debian, not arch or gentoo, to break it like that.

I found a solution - add a line to the php7.3-fpm.service unit:
RuntimeDirectory=php

Everything is working. But the question still remains why this happened. Indeed, quite after some future update, the php7.3-fpm.service unit file will be overwritten.

Answer 1

Could this be related?
ISPmanager deletes /var/run/mariadb after server restart?

Answer 2

The user under which the unit is running does not have write permissions to /run

Answer 3

finish the systemd.