I have some questions I don't understand

[JQiue]

root@archlinux ~/D/r/t/debug (main)# ll
total 36M
drwxr-xr-x 1 root root 1.4K Nov 16 14:02 build/
drwxr-xr-x 1 root root  17K Nov 16 14:06 deps/
drwxr-xr-x 1 root root    0 Nov 16 13:57 examples/
drwxr-xr-x 1 root root  572 Nov 16 14:06 incremental/
-rwxr-xr-x 2 root root  36M Nov 16 14:06 rust-demo*
-rw-r--r-- 1 root root  151 Nov 16 14:06 rust-demo.d
root@archlinux ~/D/r/t/debug (main)# sudo ser create ./rust-demo
Service rust-demo created at /etc/systemd/system/rust-demo.ser.service. To start run `ser start rust-demo`
+-----+-----------+--------+----------------+-------+--------+
| pid | name      | active | enable on boot | cpu % | memory |
+-----+-----------+--------+----------------+-------+--------+
| 0   | rust-demo | failed | false          | 0     | 0      |
+-----+-----------+--------+----------------+-------+--------+
root@archlinux ~/D/r/t/debug (main)# ser start rust-demo
service started: /org/freedesktop/systemd1/job/31947
+-----+-----------+--------+----------------+-------+--------+
| pid | name      | active | enable on boot | cpu % | memory |
+-----+-----------+--------+----------------+-------+--------+
| 0   | rust-demo | failed | false          | 0     | 0      |
+-----+-----------+--------+----------------+-------+--------+
root@archlinux ~/D/r/t/debug (main)# sudo ser logs rust-demo
Nov 19 21:15:31 archlinux (ust-demo)[19872]: rust-demo.ser.service: Failed to locate executable rust-demo: No such file or directory
Nov 19 21:15:31 archlinux (ust-demo)[19872]: rust-demo.ser.service: Failed at step EXEC spawning rust-demo: No such file or directory
Nov 19 21:15:31 archlinux systemd[1]: Started Servicer:rust-demo.
Nov 19 21:15:31 archlinux systemd[1]: rust-demo.ser.service: Main process exited, code=exited, status=203/EXEC
Nov 19 21:15:31 archlinux systemd[1]: rust-demo.ser.service: Failed with result 'exit-code'.
Nov 19 21:15:36 archlinux (ust-demo)[19887]: rust-demo.ser.service: Failed to locate executable rust-demo: No such file or directory
Nov 19 21:15:36 archlinux (ust-demo)[19887]: rust-demo.ser.service: Failed at step EXEC spawning rust-demo: No such file or directory
Nov 19 21:15:36 archlinux systemd[1]: Started Servicer:rust-demo.
Nov 19 21:15:36 archlinux systemd[1]: rust-demo.ser.service: Main process exited, code=exited, status=203/EXEC
Nov 19 21:15:36 archlinux systemd[1]: rust-demo.ser.service: Failed with result 'exit-code'.
Nov 19 21:22:52 archlinux (ust-demo)[20461]: rust-demo.ser.service: Failed to locate executable rust-demo: No such file or directory
Nov 19 21:22:52 archlinux (ust-demo)[20461]: rust-demo.ser.service: Failed at step EXEC spawning rust-demo: No such file or directory
Nov 19 21:22:52 archlinux systemd[1]: Started Servicer:rust-demo.
Nov 19 21:22:52 archlinux systemd[1]: rust-demo.ser.service: Main process exited, code=exited, status=203/EXEC
Nov 19 21:22:52 archlinux systemd[1]: rust-demo.ser.service: Failed with result 'exit-code'.

[FKPSC]

did you try ser cat rust-demo to see what was created?