AnswerBun.com

resolv.conf always empty

Unix & Linux Asked by marc on December 6, 2020

I have 2 different embedded devices…an old one running TI arago Linux and a Xilinx device (petalinux).

On both I see the same outcome when adding dns-nameservers to /etc/network/interfaces and reconfiguring the network with /etc/init.d/networking restart or rebooting the device:
The /etc/resolv.conf file always stays empty.

No dhclient, resolvconf package, network-manager daemon or mdns are present in the system.

Here the /etc/network/interfaces:

# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
    address 192.168.1.2
    netmask 255.255.255.0
    gateway 192.168.1.1
    dns-nameservers 192.168.1.1

and resolv.conf:

[[email protected]:~] ls -l /etc/resolv.conf 
lrwxrwxrwx    1 root     root           20 Feb  3 18:17 /etc/resolv.conf -> /var/run/resolv.conf
[[email protected]:~] ls -l /var/run/resolv.conf
-rw-r--r--    1 root     root            0 Feb  3 18:17 /var/run/resolv.conf

While executing /etc/init.d/networking restart, both devices call basically ifdown -a and then ifup -a, being both ifup and ifdown busybox utilities in this case.

In case mentioning the immutable file attributes solution: I don’t want to generate manually the resolv.conf file and change the file attributes to make it immutable (chattr +i), because it seems completely against how the system was designed. Why is then resolv.conf stored in volatile memory (generated by populate-volatile.sh) in the first place, if it should be permanent?

Thanks for any hints!

Update: found the solution, but will leave the question, for the sake of somebody searching for it.

One Answer

Create a script in /etc/network/if-up.d/dns with this content (in this example only eth0 is taken into account):

#!/bin/sh
if [ "$IFACE" = "eth0" ];then
for NS in $IF_DNS_NAMESERVERS; do
R="${R}nameserver $NS
"
done
echo "$R" > /etc/resolv.conf
fi

Make it executable with chmod +x /etc/network/if-up.d/dns.

Everytime you reboot the device or restart the networking services, resolv.conf will be recreated. Works like a charm!

PS: If you use another directive/naming than dns-nameservers in /etc/network/interfaces...for example my-dns, then replace $IF_DNS_NAMESERVERS with $IF_MY_DNS. Although it's cool to know, I would rather stick to conventions and use dns-nameservers.

Answered by marc on December 6, 2020

Add your own answers!

Related Questions

Set permanent environment variable for all shells

0  Asked on October 31, 2021 by user14492

         

How does jq work with keys containing slash?

1  Asked on October 31, 2021 by fhcat

 

GRUB not showing up in Pop!_OS

1  Asked on October 31, 2021

       

Set scale for bc inside a variable

1  Asked on October 31, 2021 by mdem7705

   

partition size vs file system size

1  Asked on October 31, 2021 by fa7eme

       

Explanation for “Killed Process”

1  Asked on October 31, 2021 by althor

 

tracking list of installed packages with git

2  Asked on October 31, 2021 by 400-the-cat

     

Ask a Question

Get help from others!

© 2022 AnswerBun.com. All rights reserved. Sites we Love: PCI Database, MenuIva, UKBizDB, Menu Kuliner, Sharing RPP, SolveDir