How to set systemd service dependencies?

Question

During CentOS 7 system boot nginx start fails with the following error:

2014/08/04 17:27:34 [emerg] 790#0: bind() to a.b.c.d:443 failed (99: Cannot assign requested address)

I suspect this is happening due to the network interfaces not being up yet before attempting to bind to that IP address for serving a vhost over SSL.

My guess is I need to specify the network.service as a requirement for the nginx.service, but I can't find the network service in /etc/systemd/ at all.

How can I configure the service order or dependencies in systemd?

Aren't you looking more for service *dependencies* than *order*? — user, Aug 04 '14 at 15:48
This may help: http://serverfault.com/questions/482730/systemd-dependencies-and-boot-order — Belmin Fernandez, Aug 04 '14 at 16:02
Thanks, that solves it! Mind to put it in an answer so I can close it? :) — vincent.io, Aug 04 '14 at 16:05
Deleted my answer. Source of that answer posted (Mr. Hampton). Should mark his as the correct answer. — Belmin Fernandez, Aug 04 '14 at 18:25

score 24 · Accepted Answer · answered Aug 04 '14 at 16:30

24

You need, at minimum, After=network.target in the [Unit] section of your unit file, to ensure that the network is up before starting nginx. I have no idea why your unit file doesn't have it.

Here is a complete example from my handy Fedora system, as shipped by Fedora:

[Unit]
Description=The nginx HTTP and reverse proxy server
After=syslog.target network.target remote-fs.target nss-lookup.target

[Service]
Type=forking
PIDFile=/run/nginx.pid
ExecStartPre=/usr/sbin/nginx -t
ExecStart=/usr/sbin/nginx
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s QUIT $MAINPID
PrivateTmp=true

[Install]
WantedBy=multi-user.target

answered Aug 04 '14 at 16:30

Michael Hampton

237,123
42
477
940

Thanks, great answer! I installed nginx from the remi repository (third-party), which might explain why "After" is missing in the unit file. – vincent.io Aug 05 '14 at 08:36
1

Interesting. I would drop him a note and let him know about the problem. His packages are usually very high quality and I'm not sure how he missed that. – Michael Hampton Aug 05 '14 at 12:47
Great suggestion, done. – vincent.io Aug 06 '14 at 18:44

score 10 · Answer 2 · answered Mar 11 '15 at 15:42

From the error log, it looks like your nginx config. file has a listen directive with an explicit ip address:

listen a.b.c.d:443

This means that nginx won't start unless your network interface is up and the IP a.b.c.d has been assigned to the interface.

You have two options:

change the listen directive to: listen 443; (bind to all ip addresses)
make nginx depend on network-online.target

As described in http://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/ the network.target only indicates that the network management stack is up [...] Whether any network interfaces are already configured when it is reached is undefined.

If you want to make sure that the IP address is already assigned and the interface is up, you need to add the network-online.target to your nginx's systemd unit file.

Your /etc/systemd/system/multi-user.target.wants/nginx.service file should have network-online.target in the After= and Requires= lines.

[Unit]
Description=The nginx HTTP and reverse proxy server
After=syslog.target network.target remote-fs.target nss-lookup.target network-online.target
Requires=network-online.target

[Service]
Type=forking
PIDFile=/run/nginx.pid
ExecStartPre=/usr/sbin/nginx -t
ExecStart=/usr/sbin/nginx
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s QUIT $MAINPID
PrivateTmp=true

[Install]
WantedBy=multi-user.target

+1 for mentioning `network-online.target` - in case somebody is also wondering: yes, both `Requires=` and `After=` are necessary because `Requires=` (arguably surprisingly) doesn't imply an ordering between the required unit and the requiring one. — maxschlepzig, Aug 05 '16 at 07:51

How to set systemd service dependencies?

2 Answers2

Linked