On Fri, 2011-08-26 at 19:49 +0930, Tim wrote: > On Thu, 2011-08-25 at 23:33 -0700, Paul Allen Newell wrote: > > I went back through archives of my installs and found a sufficiently > > different factory-install of /etc/hosts that I wanted to post it for > > comment given your "bad idea to bodge (sic?) anything else into those > > two lines. I checked 3 machines and they are the same, so I submit > > only one: > > +++ > > cat /etc/hosts > > 127.0.0.1 chalupa.localdomain chalupa localhost.localdomain localhost localhost4 > > ::1 chalupa.localdomain chalupa localhost6.localdomain6 localhost6 > > +++ > > Yes, it's a common thing to see (Fedora's install routine shoving them > in there). And *can* be a common problem. Not always, but when you > start having weird name resolution issues with some servers, it's the > first thing to sanitize. > > The format of the hosts file is the IP address, the (full) named address > for that IP, and a list of optional aliases. Any lookup for the name to > go with an IP will return the first name in the list. Any lookup for > the IP will match any name in the list. > > So, using your list, anything that wants to find the name to go with > 127.0.0.1 will be told chalupa.localdomain. Traditionally, it ought to > be localhost. > > Conversely, it would be traditional that any lookup to find the IP > address for the machine name (chalupa.localdomain) would find the IP it > uses on the network (192.168.2.10), but yours would return 127.0.0.1, > because it's the first answer that matches. You could counter that by > putting the 192.168... lines above the local lines. > > I seem to recall one reason why machine names were bodged into the local > loopback lines harking back to people insisting their machine name was > applied (in some other configuration file), rather than letting the > machine work it out for itself, and trying to start up their machine > when not connected to the network, and some service complaining that it > couldn't connect so it wouldn't start. I seem to recall X refusing to > start, at one point (it's been a very long time since I've seen that, > though, maybe before Red Hat Linux became Fedora). I've certainly seen > the GDM login screen change from using my hostname.domain name to > localhost.localdomain, at times that the ethernet interface wasn't up at > the time (though it's been a long time since I saw that behaviour, many > releases ago). > > It's probably not going to cause most people any problems. But you were > having some strange names in your mail headers. Whether that *really* > makes any problems other than an issue for you trying to work out where > your mail has been through, I don't know. Since your mail tests were > going up the spout, I'd have tweaked things to work in the traditional > way, to minimise any chance of this being a part of the problem, and to > make debugging mail headers much easier. > > > > This was snapped after I had installed F14 and before I edited hosts > > to know about the other machines. No comment about "Do not > > remove" (that vanished a couple of releases ago if my memory is > > correct) and it makes sense that /etc/hosts would have both the > > machine name as defined during the install and the "generic" > > localhost. > > There's some logic to it, the idea being that your machine stays named > the same, even if it can't connect to a network. > > The "do not modify the file" warning was always badly worded. It told > you not to modify a file that had already been modified, few people > would have seen the contents before that happened. > > But, it has been known to cause some people problems. And putting non- > local loopback addresses into the local loopback lines has been debated > many times in the past. And not just with Linux boxes. ---- many words but nothing substantive I'm not an expert on this by any means but I gather that for many years, UNIX & Linux systems all had fixed IP addresses and software developers relied upon matching the system hostname to the addresses in /etc/hosts to decide which interfaces they should start their daemons on. Those that serviced the loopback address as well as external addresses worked find when the hostname was entered on the 127.0.0.1 line but some were terribly confused thus begging to the administrator of the system to move real hostnames off the 127.0.0.1 address and onto the lines that listed the actual ethernet interfaces. As Linux became mainstream and dhcp-client became a normal for many linux systems, software developers had to resort to other methods for determining which interfaces to operate with. For dhcp systems, the only real place to put the actual hostname is on the 127.0.0.1 line. Now if you turn off NM, turn on 'network' and manually configure the IP addresses for your ethernet interface(s), then by all means put the real hostnames on lines other than 127.0.0.1 In reality, it shouldn't much matter though unless you are dealing with uncooperative software. Craig -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
