I have Automotive Grade Linux (Halibut 8.0.0) installed on a Qualcomm board.
This is an embedded system with no package manager, no build tools and no working DNS, but I can bring up ethernet okay.
sa8155:~# ifconfig eth0 up
sa8155:~# udhcpc
udhcpc: started, v1.29.3
udhcpc: sending discover
udhcpc: sending select for 10.0.0.112
udhcpc: lease of 10.0.0.112 obtained, lease time 604800
/etc/udhcpc.d/50default: Adding DNS 75.75.75.75
/etc/udhcpc.d/50default: Adding DNS 75.75.76.76
Notice that DHCP reports that the name servers are being retrieved correctly.
And I can ping the name servers:
sa8155:~# ping 75.75.75.75
PING 75.75.75.75 (75.75.75.75): 56 data bytes
64 bytes from 75.75.75.75: seq=0 ttl=58 time=8.973 ms
64 bytes from 75.75.75.75: seq=1 ttl=58 time=19.634 ms
64 bytes from 75.75.75.75: seq=2 ttl=58 time=11.391 ms
However, I cannot use DNS to resolve any names.
sa8155:~# nslookup debian.org
nslookup: write to '127.0.0.1': Connection refused
;; connection timed out; no servers could be reached
I noticed that /etc/resolv.conf is empty other than this comment:
sa8155:~# cat /etc/resolv.conf
# Generated by Connection Manager
I tried manually editing /etc/resolv.conf like so:
sa8155:~# cat /etc/resolv.conf
# Generated by Connection Manager
search example.com local.test
nameserver 75.75.75.75
nameserver 75.75.76.76
But that seems to disable the ethernet interface altogether.
I tried manually adding a single host and ip address pair to /etc/hosts, but I could not edit that file even though I am root.
sa8155:~# ls -alF /etc/ | grep host
-rw-r--r-- 1 root root 26 Nov 13 2019 host.conf
-rw-r--r-- 1 root root 111912 Nov 13 2019 hostapd.conf
-rw-r--r-- 1 root root 7 Nov 13 2019 hostname
-rw-r--r-- 1 root root 237 Nov 13 2019 hosts
-rw-r--r-- 1 root root 0 Nov 13 2019 hosts.allow
-rw-r--r-- 1 root root 0 Nov 13 2019 hosts.deny
sa8155:~# chmod 766 /etc/hosts
chmod: changing permissions of `/etc/hosts': Read-only file system
So I tried using ConnMan to add the DNS entries.
However, connmanctl services does not return the expected list.
sa8155:~# connmanctl services
Error: The name net.connman was not provided by any .service files
sa8155:~#
I originally posted this question here and one responder suggested that systemd-networkd might be competing with connman.
I have verified that both services are running:
sa8155:~# systemctl --type=service | grep network
systemd-networkd.service loaded active running Network Service
sa8155:~# systemctl --type=service | grep conn
connman.service
However, my understanding is that the configuration files for systemd-networkd are located here:
/etc/systemd/network
And this directory is empty for me.
It was also suggested that /etc/nsswitch.conf might be configured incorrectly.
Here is what mine looks like:
sa8155:/etc/systemd/network# cat /etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.
passwd: compat
group: compat
shadow: compat
hosts: localuser files myhostname mdns4_minimal [NOTFOUND=return] dns
networks: files
protocols: db files
services: db files
ethers: db files
rpc: db files
netgroup: nis
sa8155:/etc/systemd/network#