[Solved] - Loss of DNS

[fred44nl]

my Debian server is running Debian 10 - Buster.
recently updated to Debian 4.19.0-25-amd64 - Debian 4.19.289-1
sometimes I loose DNS
when that happens, I can not ping any outside website.
my solution is, to reboot my server
that always sobes the problem
but there must me an easier way to get DNS back, I hope

any suggesntions ??

[Aki]

Hello,
What have you done to try to find out why this happened?

[fred44nl]

sorry, I am more of an amateur
so I find that DNS stopted working and I only know, that a reboot does solve the problem and bring DNS back, of course
I am open for suggestions

[Northpoint]

When its working correctly, Check your /etc/resolv.conf file and post its contents. Then when its not post the contents again.

Also, Please post the output of :

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ip addr

and

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ip route

[fred44nl]

thank you so far.
here is the output when working.
will come back when not working.

fred44nl@Debian:~$
fred44nl@Debian:~$ cat /etc/resolv.conf
# Generated by dhcpcd from eno1.dhcp
# /etc/resolv.conf.head can replace this line
domain WORKGROUP
nameserver 1.1.1.1
nameserver 192.168.1.1
# /etc/resolv.conf.tail can replace this line
fred44nl@Debian:~$


fred44nl@Debian:~$
fred44nl@Debian:~$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
link/ether 00:01:c0:20:75:6d brd ff:ff:ff:ff:ff:ff
3: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 00:01:c0:20:75:6e brd ff:ff:ff:ff:ff:ff
inet 192.168.1.29/24 brd 192.168.1.255 scope global noprefixroute eno1
valid_lft forever preferred_lft forever
inet6 fe80:9622:ce1:d7e/64 scope link
valid_lft forever preferred_lft forever
fred44nl@Debian:~$


fred44nl@Debian:~$
fred44nl@Debian:~$ ip route
default via 192.168.1.1 dev eno1 proto dhcp src 192.168.1.29 metric 203
192.168.1.0/24 dev eno1 proto dhcp scope link src 192.168.1.29 metric 203
fred44nl@Debian:~$

[Northpoint]

Ok, Now we have a 'base' of the proper working network setup. When the network fails then repost the output of the commands again so we can see if anything has changed. You save the output of the commands to a file by redirecting it in each command. Just append this to the end of each command and give it a new file name (network-error-1, network-error-2 ect... :

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> network-error.txt

[sunrat]

@fred44nl please use code tags for terminal text output.

[fred44nl]

it has been a very long time before the network problem came back.
but as before DNS is not working, meaning that I cannot access outside servers or websites.
below, I will post the output of the commands for inspecting this.
from what I can see the file /etc/resolv.conf is empty.
it has a size of 0 bytes.

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fred44nl@Debian:~$ ip route
default via 192.168.1.1 dev eno1 proto dhcp src 192.168.1.29 metric 203 
192.168.1.0/24 dev eno1 proto dhcp scope link src 192.168.1.29 metric 203 
fred44nl@Debian:~$ 

this looks the same as before.

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ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether 00:01:c0:20:75:6d brd ff:ff:ff:ff:ff:ff
3: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:01:c0:20:75:6e brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.29/24 brd 192.168.1.255 scope global noprefixroute eno1
       valid_lft forever preferred_lft forever
    inet6 fe80::2b70:9622:ce1:d7e/64 scope link 
       valid_lft forever preferred_lft forever

this also looks the same for me.

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fred44nl@Debian:~$ cat /etc/resolv.conf
fred44nl@Debian:~$ 

as you can see nothing appears.

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fred44nl@Debian:~$ ls -al /etc/resolv.conf
-rw-r--r-- 1 root root 0 mei  2 01:16 /etc/resolv.conf
fred44nl@Debian:~$ 

the file is empty

I will go and find the contents of resolv.conf and make the file original again.
see what happens

edit1:
after restoring the file /etc/resolv.conf, DNS was working again properly.

edit2:
My machine is now updated from Buster to Bullseye

[Aki]

Hello,

[..]
I will go and find the contents of resolv.conf and make the file original again.
see what happens

edit1:
after restoring the file /etc/resolv.conf, DNS was working again properly.

edit2:
My machine is now updated from Buster to Bullseye

I'm glad you sorted it out. :)

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