Is there a safe way to automatically remove a stray unix-socket files before it’s related services are run?

Solution 1:

Use tmpfs, e.g. create the file inside /dev/shm.

It is intended to appear as a mounted file system, but stored in volatile memory instead of a persistent storage device.

^{[emphasis mine]}

In my Debian /run is also tmpfs and I can see few tools have created their sockets there. According to FHS /run is a good place for a socket created by a system-wide service.

Run-time variable data: Information about the running system since last boot, e.g., currently logged-in users and running daemons. Files under this directory must be either removed or truncated at the beginning of the boot process; but this is not necessary on systems that provide this directory as a temporary filesystem (tmpfs).

In my Debian /run belongs to root and its mode bits (permissions) are rwxr-xr-x. Normal users cannot benefit from it.

On the other hand /dev/shm is rwxrwxrwt, anyone can use it. But since it's a "common land" (like /tmp), few problems arise. Possibility of name conflicts is one of them. Two users may disturb each other even if their intentions are perfectly harmless.

Then there is /run/user/$uid, also as tmpfs:

used for storing files used by running processes for that user. […]
This directory is local to the system and only accessible by the target user. So applications looking to store their files locally no longer have to worry about access control.