Questions[dhcp](ubuntu)

I know there are other posts here asking this, but those suggestions do not help, the configuration keeps changing and I simply cannot get my own changes to persist.

I have the Google 8.8.8.8 and 8.8.4.4 servers in my Network Manager configuration in the GUI, and

systemd-resolv --status returns

Link 2 (enp38s0f1)
      Current Scopes: DNS    
DefaultRoute setting: yes    
       LLMNR setting: yes    
MulticastDNS setting: no     
  DNSOverTLS setting: no     
      DNSSEC setting: no     
    DNSSEC supported: no     
  Current DNS Server: 8.8.8.8
         DNS Servers: 8.8.8.8
                      8.8.4.4
          DNS Domain: ~.   

Nevertheless, dig google.com shows

;; Query time: 0 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Mon Oct 05 11:08:26 EDT 2020
;; MSG SIZE  rcvd: 83

so my default route 192.168.1.1 as DNS. Furthermore, /etc/resolv.conf is a symlink to /run/systemd/resolve/resolv.conf, which in turn reads

# Generated by dhcpcd from enp38s0f1.dhcp, wlp0s20f3.dhcp
# /etc/resolv.conf.head can replace this line
domain fios-router.home
nameserver 192.168.1.1
# /etc/resolv.conf.tail can replace this line

The only enp38s0f1.dhcp file on this system (I've searched /) is /run/dhcpcd/resolv.conf/enp38s0f1.dhcp, which reads

# Generated by dhcpcd from enp38s0f1.dhcp
domain fios-router.home
search fios-router.home
nameserver 192.168.1.1

I have tried to write in other nameservers there, but they do not persist. In the past I've made the changes persistent by making the file immutable with chattr +i, but

lsattr /run/dhcpcd/resolv.conf/enp38s0f1.dhcp

returns

lsattr: Inappropriate ioctl for device While reading flags on /run/dhcpcd/resolv.conf/enp38s0f1.dhcp

so that attribute is not available here. And besides, I shouldn't have to make the file immutable anyway: there should presumably be some way I can control the DNS server..

Edit:

In response to comments below:

$ dpkg -l *dnsmasq*
---
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name             Version         Architecture Description
+++-================-===============-============-============================================
un  dnsmasq          <none>          <none>       (no description available)
ii  dnsmasq-base     2.80-1.1ubuntu1 amd64        Small caching DNS proxy and DHCP/TFTP server
un  dnsmasq-base-lua <none>          <none>       (no description available)

I've been attempting to figure this out for 5 hours now. Hopefully someone who is more knowledgeable, can help me out.

Randomly, without me making any changes to my device, my internet cut out. I tried to ping Google DNS, but was met with sendmsg: operation not permitted. I spent hours Googling this issue, and tried every solution known to man, with no success. If anything, I broke it even further.

Here is some helpful data:

$ cat /etc/network/interfaces 
auto lo
iface lo inet loopback

allow-hotplug wlp3s0
iface wlp3s0 inet dhcp

$ cat /etc/NetworkManager/NetworkManager.conf
[main]
plugins=ifupdown,keyfile,afono

[ifupdown]
managed=true

$ cat /etc/systemd/resolved.conf
[Resolve]
DNS=8.8.8.8
DNSStubListener=no

Excerpts from journalctl:

/etc/dhcpclient-enter-hooks.d/samba returned non-zero exit status 1
...
send_packet: Operation not permitted
...
dhclient.c: Failed to send 300 byte long packet over fallback interface

$ ping 8.8.8.8
ping: sendmsg: Operation not permitted

$ ping [broadcast IP] -b
ping: sendmsg: Operation not permitted

Thanks!

I'm experiencing what appears to be a name resolution issue in Ubuntu 12.04 Server edition when configuring my computer to use static ip.

In /etc/network/interfaces:

# The primary network interface
auto eth0
iface eth0 inet static
address 192.168.1.28
netmask 255.255.255.0
gateway 192.168.1.1

Running $ sudo apt-get upgrade, results in a 'Failed to fetch...':

. . . W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise-backports/universe/i18n/Translation-en_US Something wicked happened resolving 'us.archive.ubuntu.com:http' (-5 - No address associated with hostname)
[...]

When I change my /etc/network/interfaces to:

auto eth0
iface eth0 inet dhcp

Everything works fine.

Looking into /etc/resolv.conf provides some more hints.

In cases where I was getting the resolving issue, resolv.conf was empty; no nameservers were specified. Then I changed to DHCP from static and restarted networking; /etc/resolv.conf got changed to: 'nameserver 192.168.1.1'.

Switching back from DHCP to static and restarting doesn't remove the nameserver entry. But when I restarted the system with static set, resolv.conf was empty. When I restart the system with DHCP set, resolv.conf has nameserver 192.168.1.1. So, it appears that the issue is that resolve.conf is not getting written to correctly? Which package/code is responsible for writing to resolv.conf? Is there a particular package that I can take a look at open issues?

UPDATE: istream posted a good article discussing changes to resolve.conf in 12.04. http://www.stgraber.org/2012/02/24/dns-in-ubuntu-12-04/

I have just set up a new Ubuntu server and I am going to be doing a lot of networking tests.

During setup, I simply skipped the network step.

I now need to switch between DHCP and an address quite often.

I know I can easily give a port an address via ifconfig eth0 x.x.x.x netmask x.x.x.x, but, is there an alternative that can be used in order to set a port to use DHCP?

If this isn't possible, I am guessing I can default in /etc/network/interfaces to dhcp and then just use up/down or restart networking in order to apply... but, I would much rather use ifconfig.

I want Ubuntu to get the hostname and DNS name from a DHCP client. The default installation of Ubuntu 11.10 (Oneiric Ocelot) does not do that.

The same question was asked and is unsolved on Ubuntu Forums.