The question is partly a duplicate of multiple questions, but since I don't have enough reputation for commenting, this is my take on trying to understand the issue and prevent it from repeating.
So, I installed Ubuntu 21.10 on ASUS MINIPC PN51-E1 (AMD® Ryzen 7 5700u, radeon graphics AMD® Renoir) a few weeks ago and, mostly, all seemed ok. Then, the other day, probably after sudo apt upgrade, I tried to awake the computer from a sleep but it seemed frozen. I forced the shutdown by pressing long the power button.
When I restarted, I was not able to access the Internet anymore.
Many seem to have issues with networking. This, especially, helped me forward: Ubuntu Server 18.04 Temporary failure in name resolution. Apparently, there was a problem with my DNS setup, and /etc/resolv.conf might be the key (pinging returned "Temporary failure in name resolution").
I ended up removing the symlink and creating a static /etc/resolv.conf with only one line:
nameserver <ISP_DNS_server>
This recovered the Internet access. At least for the time being.
However, there are dozens of posts on problems related to /etc/resolv.conf, for example:
- resolv.conf keeps getting reset by something
- How do I get resolvconf to regenerate resolv.conf after I change /etc/network/interfaces?
- Can not edit resolv.conf
- How to make persistent changes to /etc/resolv.conf Ubuntu 18.10
After reading all these, I'm still a bit lost:
- What causes the problems?
- Is my fix a good one, and permanent?
- Should I install
resolvconf? If yes, why it isn't already installed?
For example, I first tried to create /etc/resolvconf/resolv.conf.d/base and add nameserver info there, but it did not seem to work (I don't have resolvconf installed).
