cloud-init-local.service should add Before=NetworkManager

[Bert JW Regeer]

When using systemd on CentOS 7/RHEL 7 with cloud-init configured to use ConfigDrive on OpenStack, cloud-init-local needs to have a line added to it's unit file that makes sure it gets to finish before NetworkManager is started.

Before=NetworkManager.service

NetworkManager wants target network.target, currently that means it runs at the same time as cloud-init-local, which means it will start DHCP and write /etc/resolv.conf while cloud-init-local is parsing the ConfigDrive and is writing the appropriate ifcfg-* files.

This causes a race condition with who gets to modify /etc/resolv.conf. NetworkManager does not take kindly to that race.

When NetworkManager notices the new ifcfg-* files it will turn off DHCP and mark the interfaces "unmanaged", however it doesn't notice the change made to /etc/resolv.conf.

Related to the changes made here:

https://code.launchpad.net/~bregeer-ctl/cloud-init/+git/cloud-init/+merge/305058

If NetworkManager is started after cloud-init-local, then NetworkManager will correctly see that /etc/resolv.conf is not to be touched by it.

[Joshua Harlow (harlowja)]

Adjustment @ https://code.launchpad.net/~harlowja/cloud-init/+git/cloud-init/+merge/306283

[Scott Moser (smoser)]

this is believed fixed in 17.1 for sure. possibly 0.7.9.

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/2720