How do I restart nginx only after the configuration test was successful on Ubuntu?

When I restart the nginx service on a command line on an Ubuntu server, the service crashes when a nginx configuration file has errors. On a multi-site server this puts down all the sites, even the ones without configuration errors.

To prevent this, I run the nginx configuration test first:

nginx -t

After the test ran successful, I could restart the service:

/etc/init.d/nginx restart

Or only reload the nignx site configs without a restart:

nginx -s reload

Is there a way to combine those two commands where the restart command is conditional to the configuration test's result?

I couldn't find this online and the official documentation on this is rather basic. I don't know my way around Linux that well, so I don't know if what I'm looking for is right in front of me or not possible at all.

I'm using nginx v1.1.19.

As of nginx 1.8.0, the correct solution is

sudo nginx -t && sudo service nginx reload

Note that due to a bug, configtest always returns a zero exit code even if the config file has an error.

Actually, as far as I know, nginx would show an empty message and it wouldn't actually restart if the configuration is bad.

The only way to screw it up is by doing an nginx stop and then start again. It would succeed to stop, but fail to start.

I use the following command to reload Nginx (version 1.5.9) only if a configuration test was successful:

/etc/init.d/nginx configtest && sudo /etc/init.d/nginx reload

If you need to do this often, you may want to use an alias. I use the following:

alias n='/etc/init.d/nginx configtest && sudo /etc/init.d/nginx reload'

The trick here is done by the "&&" which only executes the second command if the first was successful. You can see here a more detailed explanation of the use of the "&&" operator.

You can use "restart" instead of "reload" if you really want to restart the server.

alias nginx.start='sudo nginx -c /etc/nginx/nginx.conf'
alias nginx.stop='sudo nginx -s stop'
alias nginx.reload='sudo nginx -s reload'
alias nginx.config='sudo nginx -t'
alias nginx.restart='nginx.config && nginx.stop && nginx.start'
alias nginx.errors='tail -250f /var/logs/nginx.error.log'
alias nginx.access='tail -250f /var/logs/nginx.access.log'
alias nginx.logs.default.access='tail -250f /var/logs/nginx.default.access.log'
alias nginx.logs.default-ssl.access='tail -250f /var/logs/nginx.default.ssl.log'

and then use commands "nginx.reload" etc..

You can reload using /etc/init.d/nginx reload and sudo service nginx reload

If nginx -t throws some error then it won't reload

so use && to run both at a same time

like

> nginx -t && /etc/init.d/nginx reload

You can use signals to control nginx.

According to documentation, you need to send HUP signal to nginx master process.

> HUP - changing configuration, keeping up with a changed time zone (only for FreeBSD and Linux), starting new worker processes with a new configuration, graceful shutdown of old worker processes

Check the documentation here: http://nginx.org/en/docs/control.html

You can send the HUP signal to nginx master process PID like this:

kill -HUP $( cat /var/run/nginx.pid )

The command above reads the nginx PID from /var/run/nginx.pid. By default nginx pid is written to /usr/local/nginx/logs/nginx.pid but that can be overridden in config. Check your nginx.config to see where it saves the PID.

At least on Debian the nginx startup script has a reload function which does:

reload)
  log_daemon_msg "Reloading $DESC configuration" "$NAME"
  test_nginx_config
  start-stop-daemon --stop --signal HUP --quiet --pidfile $PID \
   --oknodo --exec $DAEMON
  log_end_msg $?
  ;;

Seems like all you'd need to do is call service nginx reload instead of restart since it calls test_nginx_config.