DNS Configuration
By default, DNS resolution on Flatcar Container Linux is handled through /etc/resolv.conf
, which is a symlink to /run/systemd/resolve/resolv.conf
. This file is managed by
systemd-resolved
. Normally, systemd-resolved
gets DNS IP addresses from
systemd-networkd
, either via DHCP or static configuration. DNS IP addresses can also be set via systemd-resolved
’s
resolved.conf
. See
Network configuration with networkd
for more information on systemd-networkd
.
Using a local DNS cache
systemd-resolved
includes a caching DNS resolver. To use it for DNS resolution and caching, you must enable it via
nsswitch.conf
by adding resolve
to the hosts
section.
Here is an example Butane Config snippet to do that:
variant: flatcar
version: 1.0.0
storage:
files:
- path: /etc/nsswitch.conf
mode: 0644
contents:
inline: |
# /etc/nsswitch.conf:
passwd: files usrfiles
shadow: files usrfiles
group: files usrfiles
hosts: files usrfiles resolve dns
networks: files usrfiles dns
services: files usrfiles
protocols: files usrfiles
rpc: files usrfiles
ethers: files
netmasks: files
netgroup: files
bootparams: files
automount: files
aliases: files
Only nss-aware applications can take advantage of the systemd-resolved
cache. Notably, this means that statically linked Go programs and programs running within Docker/rkt will use /etc/resolv.conf
only, and will not use the systemd-resolve
cache.