I am currently installing a new Gentoo system on a computer that is run by a Gentoo system that has not been updated since January 2019.
Initially, I did so by chrooting to a newly formatted disk partition. My intention was to build everything in the chrooted environment and only then start to work in the new Gentoo system. However, when after installing Grub I rebooted into the new Gentoo system to find out if it works and rebooted again into the old Gentoo system to continue compilation in the chroot environment, I found out that my computer does not have a working ethernet connection to my home router. The "ip addr" command showed that my ethernet interface is down. I tried "ip link set <eth0> up" and "ifconfig <eth0> up" commands, where <eth0> substitutes the correct, "predictable," name of my ethernet interface but it had not helped. Initially, I thought that something was wrong with my hardware, but when I rebooted into my new Gentoo system, the ethernet interface started to work again. Then, I rebooted back to the old system, and the ethernet interface stopped working again. It is very strange because I am sure that I have not changed anything on my old Gentoo system except for installing a new Grub onto the system disk. So, I have tried to reinstall (the old) Grub from my old system, but it has not helped either. Finally, I decided that it would be easier to complete installation of the new Gentoo system than to find out what is wrong with the old Gentoo system ethernet connection. So, I compiled xorg-x11, awesome, gvim, xfce4-terminal and are currently compiling firefox. Hopefully, tomorrow I will already have my new Gentoo system working. However, I am still wondering why the ethernet interface stopped working on my old Gentoo system. As, I have already said, I am pretty sure that I have not changed anything in its settings. Moreover, I have looked through the entire /etc directory of my old Gentoo system for config files that were modified during the installation of the new Gentoo system (suspecting that instead of the chrooted environment I put an installation command into the su terminal of my old Gentoo system or mistakenly edited a configuration file of my old Gentoo system) but found no config file that was modified during this period of time. So, I am not in a desperate need for help, but just interested to find out the reason for such a strange behaviour of the ethernet interface. P.S. I have read in the Gentoo Network management wiki that the connman, netifrc, dhcpcd, networkmanager, and openrc should not be run at the same time because it could lead to "unpredictable results" and checked if it is not the case on my old Gentoo system. No, on my old Gentoo system installed is only the openrc with the netifrc use flag and netifrc (which, as I guess, leads to only netifrc being used). But, anyway, it has been worked so for years and only now suddenly stopped.
