For check and restart services, if they are inactive/dead.
$ nano service_ck.sh
#!/bin/bash
STATUS=$(systemctl is-active snort)
# Most services will return something like "active" if they are in fact "active"
test "$STATUS" = "active" || systemctl restart snort
Change file permissions:
$chmod +x service_ck.sh
Update your crontab:
$sudo crontab -e
add:
# min hour day month dow cmd
*/1 * * * * /path/to/service_ck.sh
or
#every minute:
* * * * * /path/to/service_ck.sh