VM centos/7/cloud: empty /etc/resolv.conf

[lictw]

Hello! Did I find right place to post bug with official centos/7/cloud image?

Host: ubuntu/22.04 5.15.0-79-generic
LXD: 5.17
Image: Centos 7 amd64 (20230828_07:08)

The problem. With default profile:

# lxc profile show default
config: {}
description: ""
devices:
  eth0:
    name: eth0
    network: lxdbr0
    type: nic

after lxc launch images:centos/7/cloud c1 --vm there is empty /etc/resolv.conf (so no DNS resolution), but internet:

[root@c1 ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
[root@c1 ~]# ping google.com
ping: google.com: Name or service not known
[root@c1 ~]# ping -c 1 8.8.8.8
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=107 time=6.03 ms

--- 8.8.8.8 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 6.035/6.035/6.035/0.000 ms

I'm not sure I understand exactly what's going on, but:

1. centos/7 image use eth0 as network interface
2. .., but cloud-init (with default NoCloud datasource) configured for enp5s0 and it configures this device for NetworkManager (NM):

[root@c1 ~]# cat /var/lib/cloud/seed/nocloud-net/network-config 
version: 1
config:
  - type: physical
    name: enp5s0
    subnets:
      - type: dhcp
        control: auto
[root@c1 ~]# ls /etc/sysconfig/network-scripts/ifcfg-*    
/etc/sysconfig/network-scripts/ifcfg-enp5s0  /etc/sysconfig/network-scripts/ifcfg-eth0  /etc/sysconfig/network-scripts/ifcfg-lo
[root@c1 ~]# grep NM /etc/sysconfig/network-scripts/ifcfg-*
/etc/sysconfig/network-scripts/ifcfg-eth0:NM_CONTROLLED=no

3. dhcp-client runs first and configure network on eth0
4. after that runs NM, it can't manage eth0 (so can't break network), but hold (so empty) /etc/resolv.conf, and it can't handle configured enp5s0 (no such device)

So there is VM with network and without DNS. I created simple profile for temporary fix:

# lxc profile show network.centos-7 
config:
  cloud-init.network-config: |
    version: 1
    config:
    - type: physical
      name: eth0
      subnets:
      - type: dhcp
        control: auto
# lxc launch images:centos/7/cloud c2 -p default -p network.centos-7 --vm
[root@c2 ~]# cat /etc/resolv.conf 
# Generated by NetworkManager
search lxd
nameserver 10.200.30.1
[root@c2 ~]# ping -c 1 ya.ru
PING ya.ru (5.255.255.242) 56(84) bytes of data.
64 bytes from ya.ru (5.255.255.242): icmp_seq=1 ttl=246 time=14.8 ms

--- ya.ru ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 14.866/14.866/14.866/0.000 ms
[root@c2 ~]# ls /etc/sysconfig/network-scripts/ifcfg-* 
/etc/sysconfig/network-scripts/ifcfg-eth0  /etc/sysconfig/network-scripts/ifcfg-lo

[stgraber]

Is this still happening? We have automated daily tests of our images and they've not flagged this image as having an issue.