Set global DNS server in snap

snap
1

Hi,

Is it possible to set the global DNS server in a snap?

I know that by using systemd-resolved D-BUS API, it would work to set a DNS server for a specific link (tbh, I haven’t tried), according the the comment in interfaces/builtin/network_control.go:

# Allow access to the safe members of the systemd-resolved D-Bus API:
#
# https://www.freedesktop.org/wiki/Software/systemd/resolved/
#
# This API may be used directly over the D-Bus system bus or it may be used
# indirectly via the nss-resolve plugin:
#
# https://www.freedesktop.org/software/systemd/man/nss-resolve.html

Another thought is to use system-files interface and write the DNS config file to /etc/systemd/resolved.conf.d/.

Thanks.

2

Indeed, network-control does not expose a way to permanently change DNS configuration. AFAIU the SetLinkDNS is only temporary. Looking at the docs at https://www.freedesktop.org/software/systemd/man/org.freedesktop.resolve1.html the intention is for it to be called by network management software. probably the likes of systemd-networkd/NeworkManager once they get the DNS servers via DHCP.

I think that maybe you could probably produce a config for netplan which sets the DNS servers in the system. This is allowed by using network-setup-control interface.

However, I don’t think there’s a way to set DNS=... in resolved.conf without using system-files. Though, the net effect is probably identical if you just specify the same list of DNS servers in nameservers for each interface.