Systemd wait for network interface to be up before running service

Question

I have a couple questions about systemd. I'm having issues consistently getting my script to run once the network interface is up. I have tried Requires and After as seen below but is inconsistent with waiting for the network to be up. Am I using the right service and implementing it correctly? To by pass this right now I am running a ping check loop which is very inefficient and hackish. Any advice would be great. Thanks!

[Unit]
Description=PBU installer
Requires=network-online.service
After=network-online.service

[Service]
Type=oneshot
ExecStart=/home/pbu/current/scripts/pbu-unpack.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Solution 1

I solved this problem by looking at the output of:

systemctl list-units --no-pager

That showed me many units that I didn't expect like all the network devices!

sys-devices-virtual-net-lan0.device loaded active plugged   /sys/devices/virtual/net/lan

So I added

BindsTo=sys-devices-virtual-net-lan0.device
After=sys-devices-virtual-net-lan0.device

to my unit service file and then my service didn't start until lan0 was available.

Solution 2

This seems to be incorrect. The correct name is network-online.target. network-online.service does not exist (tested on Fedora 26).

https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/

Comments

[rogerdpack]

See unix.stackexchange.com/questions/210604/…

[nasataxidermprefix]

I have tried it... I'll try it again. Would i insert it as a parameter for Requires and After?

[smokes2345]

When using "Requires", all the listed service units will start together. When using "After", systemd will make sure that all other listed units will start before yours, but will not necessarily start yours with them. One or the other should be sufficient, seems to me that both would cause a conflict.

[nasataxidermprefix]

I think the problem is when I use requires OR after, the service starts with or after, but I almost need the network service to finish or at least get to a certain point... or else my script will require the network before it is actually up...

[nasataxidermprefix]

Unfortunately systemd doesn't have this option. WIsh it did, would save me a lot of trouble.

[smokes2345]

That's why I suggested using network.target. Targets indicate a particular milestone in the boot process or a group of units that work together, instead of an individual service. The idea behind using "After=network.target" is that all the units that are needed to provide network access should be activated before your unit is activated.

[0xC0000022L]

There's another catch with this method. What does it mean to be online? Just because a particular network interface is up doesn't mean that the service that I want to tie to a totally different interface can start ...