Not sure who’s at fault here, but without doing anything weird, I ended up with a system where shepherd thought that nginx was stopped, while there was still an nginx process around. I certainly didn’t start it by hand.
The result was this: $ sudo herd restart nginx Service nginx is not running. herd: exception caught while executing 'start' on service 'nginx': Throw to key `srfi-34' with args `("#<condition &invoke-error [program: \"/gnu/store/mlg0xfbiq03s812rm3v7mrlhyngas4xp-nginx-1.17.1/sbin/nginx\" arguments: (\"-c\" \"/gnu/store/r6gl9n7pwf4npiri05qxr40vdihdm2yy-nginx.conf\" \"-p\" \"/var/run/nginx\") exit-status: 1 term-signal: #f stop-signal: #f] 147e000>")’. That error message could also be clearer about what’s going on. At any rate, after I killed the nginx process, “herd start nginx” worked fine. I should add that nginx was still doing its job fine before I killed it.