[yocto] Make the service the last run in boot

[JH]

Hi,

How can I find the systemd last run service I can put it in my network
application After=<last run tartget or service>?

I need my network application service to be run at last in boot, I
made After=connman and Requires=connman.service that did not work,
always failed in boot, I have to manually restart the network
application service which won't work in field operation.

Searched from Internet, there is a blog Systemd: Run it last to create
a custom.target After=multi-user.target, and put my network
application service WantedBy=custom.target, that works well, but it is
a little bit cumbersome to configure customer.target in Yocto bb file,
enabling the customer.target is called systemctl isolate
custom.target, the /etc/systemd/system/default.target link needs be
changed to from multi-user.target to custom.target. I am not sure how
it could be done in do_install, appreciate your tips.

Thank you.

Kind regards,

- JH