support NTPSERVERARGS in /etc/sysconfig/network

[Brendan Germain]

I'm not sure what's changed but in previous versions of cloud-init, it was not owning/writing contents to /etc/sysconfig/network.

I DHCP my ntp endpoints and provide ntp options via NTPSERVERARGS. Example:

echo 'NTPSERVERARGS="minpoll 3 maxpoll 4"' >> /etc/sysconfig/network

$ grep server /etc/ntp.conf
server 10.155.55.1 minpoll 3 maxpoll 4 # added by /sbin/dhclient-script

On boot now /etc/sysconfig/network only has:
$ cat /etc/sysconfig/network
# Created by cloud-init on instance boot automatically, do not edit.
#
NETWORKING=yes

So how can i prevent cloud-init from modifying it, or have it write the additional option (NTPSERVERARGS) that i need?

[Ryan Harper (raharper)]

Hello,

Thanks for file a bug. Cloud-init has included a sysconfig renderer for quite some time. It does indeed render the contents of /etc/sysconfig/network.

The sysconfig renderer doesn't currently support adding additional values through the network configuration format.

We should see if we can read/update the contents of the file instead of writing one from scratch.
There is an existing update_sysconfig_file, so we should take a look at using that instead.

[Manuel Torrinha (t0rrant)]

This also denies users from adding options like:

  RES_OPTIONS="rotate"

which can be useful in scenarios where multiple networks have different
nameservers for each network.

[Dan Watkins (oddbloke)]

Hi Manuel,

Thanks for the additional information! It sounds like this bug affects you, would you be interested in looking into contributing a fix for it?

Thanks!

Dan

[Manuel Torrinha (t0rrant)]

Hi Dan,

I'll take a look next week and see what I can do.

If in the meantime someone else comes up with a solution, even better.

Any considerations I should have besides the instructions in:

  https://cloudinit.readthedocs.io/en/latest/topics/hacking.html

i.e: good practices for contributing.

Cheers,
Manuel

[Dan Watkins (oddbloke)]

Hi Manuel,

That's certainly a great place to start! For this particular bug, I expect that the `cloud-init devel net-convert` command (https://cloudinit.readthedocs.io/en/latest/topics/network-config.html#network-configuration-tools) would be useful; that will allow you to iterate on the network configuration generation code without having to build a cloud-init package, install it in an instance and reboot. (You should be able to run this from your development environment, if you install cloud-init into a virtualenv, for example. Don't install cloud-init at the system level on your development machine!)

The team is generally around in #cloud-init on Freenode, if you have any further questions. (FYI, the cloud-init team happens to be largely North America based, so the most activity from core team members is in US working hours.)

Thanks!

Dan