You can copy contrib/systemd/asterisk.service to /usr/lib/systemd/system and then use systemctl start|stop|status asterisk etc. You do not need the socket files.
COS9 has the necessary files and libs for Asterisk, but I couldn’t get res_srtp to work. The system installed lib_srtp2 failed in srtp_init() which lead to
[Jan 21 13:30:24] WARNING[68335]: res_srtp.c:1238 res_srtp_init: Failed to initialize libsrtp
[Jan 21 13:30:24] ERROR[68335]: loader.c:2508 load_modules: *** Failed to load module res_srtp.so
[Jan 21 13:30:24] ERROR[68335]: asterisk.c:3938 check_init: Module initialization failed. ASTERISK EXITING!
Without res_srtp.so everything seems to run smoothly.