On Friday, January 21, 2022 10:46:35 PM EST Greg Wooledge wrote: > On Fri, Jan 21, 2022 at 09:34:35PM -0500, gene heskett wrote: > > /etc/resolv.conf has: > > search coyote.den > > nameserver 192.168.xx.1 > > > > the search line says to look in the /etc/hosts file, failing that, > > the > > nameserver line sends the dns lookup query to the router > > No, that's not correct. > > The config file that says "look in /etc/hosts first, then look in DNS > next" is /etc/nsswitch.conf. Specifically, it's the line that begins > with "hosts:" in that file. > > The "search" line in /etc/resolv.conf means "if I type ftp roadrunner, > I want it to act as if I had typed ftp roadrunner.coyote.den". > > In other words, it's the default DNS search domain for looking up the > *other computers* on your local area network. > > > However when I set hostname with hostname, the 169.bs stays out of > > the > > picture and networking works the world until a reboot. > > Well, yes. The "hostname" command sets the current hostname, which > resides in memory only. It has no permanent effect. > > And it has nothing at all to do with IP addresses. Or DNS. > > > Setting the hostname with hostnamectl to the alias in /etc/hosts for > > this machine, gets me exactly the same hostname but then the route > > reported by "ip a" is the 169.bs.bs.bs and I can't get out of my > > shirt pocket to even ping the router at 192.168.xx.1. > > Routing has nothing to do with your system's hostname. At all. > > At the most basic level, your system's default route is set by whatever > mechanism sets up your network interfaces. On Debian, this can be any > of *several* different pieces of software, depending on what's > installed and what you've got in your config files. > > In the *most* basic possible configuration, your routing table will be > one automatic entry for your ethernet interface (created from the IP > address and netmask which are assigned to that interface), and then one > "default" route which is assigned for reaching every host that's *not* > part of your LAN. > > E.g. in /etc/network/interfaces you'd have something like this: > > auto enp2s0 > > iface enp2s0 inet static > address 192.168.1.21/24 > gateway 192.168.1.1 > > This tells the "ifupdown" software package that you'd like it to manage > the enp2s0 network interface, assigning the IP address 192.168.1.21 > with a 24-bit netmask, which automatically creates a route to the > 192.168.1.0/24 network. In addition, it will create a default route > via the 192.168.1.1 address. > > None of this has *anything* to do with your system's hostname. > > None of this has *anything* to do with your /etc/hosts file. > > None of this has *anything* to do with DNS. > > Of course, there are many other ways to configure network interfaces in > Debian. You might be using Network-Manager, for example. Or > systemd's systemd-networkd(8). Or you might be using > /etc/network/interfaces but telling it to ask for configuration from > DHCP. > > Also, by the way, "ip a" does not report routes. That's "ip r". > > unicorn:~$ ip r > default via 10.0.0.1 dev lan0 > 10.0.0.0/24 dev lan0 proto kernel scope link src 10.0.0.7 > > ------------------------------------ > > You're probably still confused. Let's go over everything again, from > the beginning. > > Your computer has a *network interface*. This interface has some kind > of name. The names are very complicated and I don't want to introduce > that particular piece of complexity here. Let's say that you've > somehow managed to determine your interface's name. Let's say, for > this example, that your interface's name is enp2s0. > > In order for your network interface to *work*, it has to be assigned an > IP address and a netmask. This can come from DHCP, or it can come > from files that you configure on your system. > > With an IP address and a netmask, you will be able to communicate with > other computers on your *local area network*, by using their IP > addresses. > > If you have a default route, then you can potentially talk to computers > *outside* of your LAN. This default route can come from DHCP, or from > local files. E.g. with a properly configured default route, you will > be able to run commands like "ping 8.8.8.8" and get responses. > > If you'd like to communicate with other computers by name instead of by > IP addresses, you can either put their names and IP addresses in the > /etc/hosts file (a simple text file), *or* you can configure your > computer to use DNS. > > DNS is configured in the /etc/resolv.conf file. The most basic piece > consists of "nameserver" lines which contain the IP addresses of DNS > resolvers which will look up computer names for you. These nameservers > can come from DHCP, or they can be configured in your local files. > > Your computer can also have a hostname. This is how your computer > identifies itself when it logs things, so that you can tell which > computer wrote which piece of the logfile. Your computer can be named > whatever you like. Its name has meaning only to you. Other computers > do not know what your hostname is, and they do not care. > > If you want other computers to be able to contact you by a name, then > you add that name to DNS, *or* to the /etc/hosts files of those other > computers. The name that you put in DNS or other machines' /etc/hosts > files does *not* have to be the same as your hostname. Your hostname > is private. It's what your computer calls itself. It's not what > other computers call you. > > Your computer can also have a *list of search domains* for use in > hostname lookups. This is typically something you'd only care about > if you have a LAN with multiple computers on it, which all want to > talk to each other. If you're just a single computer that's on the > Internet, you *do not care* about this at all. > > The main purpose of a list of search domains is to save typing. Let's > say you've got a LAN with hosts that are (publically) called > "cat.coyote.den" and "dog.coyote.den". If you want to log into the > first one, you could type "ssh cat.coyote.den". But that's a lot of > typing. If you have "coyote.den" in your list of search domains, then > you can simply type "ssh cat". The host resolver will try each of the > domains in your search list, one by one, as suffixes, until one of > them works. > > This list of search domains is configured in your local > /etc/resolv.conf file. It can be a static entry, or it can come from > DHCP. > > . This is all well and good, Greg, but it still does NOT give a clue what todo when the system picks a fictitious route out of its rear.
And that IS my squawk. I did find a fix as posted earlier, but I doubt it will work under a pine tree in Wash State where these two cards will get mailed to once I get a realtime kernel installed and working. And I've got a v5.16.0-rc6-rt12, downright bleeding edge to install tomorrow. Cheers Greg, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
