From: tg@debian.org 
  
 Someone (not clear from the web view, and l.d.o does not allow 
 downloading posts as mbox like the BTS does) wrote: 
  
 > why we are writing an /etc/hosts with "127.0.1.1 apollo.example.com apollo" 
  
 Hah! *rubs hands* Hostnames on unixoid systems€€€ a pet peeve. 
  
 First off, that 127.0.1.1 has to go. There are active changes 
 underways to change the 127/8 allocation to an 127/24 one, to 
 free more IPv4 addresses. (Just passing on, don€€€t talk to me 
 about this one.) 
  
 Then. 
  
 /etc/hosts. 
  
 I€€€ve worked best with the following setup: 
  
 1. If any IP or Legacy IP address is statically assigned to 
    the box (€€€inet static€€€/€€€inet6 static€€€ in /e/n/i, or even 
    it€€€s known that the host has a reservation on the dhcpd) 
    then add lines of the form €€€$ip $fqdn ${fqdn%%.*}" 
  
 2. If there is any Legacy IP statically assigned as in 1, 
    then add additionally €€€127.0.0.1 localhost€€€€€€, 
    else add additionally €€€127.0.0.1 $fqdn ${fqdn%%.*} localhost€€€€€€ 
  
 3. Add the remaining IP entries like ::1€€€ 
  
 Additionally, /etc/{host,my}name or however the OS calls the file€€€ 
 the kernel nodename is loaded from (which will be the result of the 
 bare €€€hostname€€€ command without -f/-s) m€€u€€s€€t€€ €€c€€o€€ 
 €€t€€a€€i€€n€€ €€t€€h€€e€€ €€F€€Q€€D€€N€€! This 
 is not what Debian currently does but is necessary and will lead to 
 only minor fallout (like the FQDN shown in the too-short field of 
 KDM€€€s greeter) that€€€s easily handled by s/\\..*$// in affected code, 
 but will result in a MUCH better overall operation. 
  
 The /etc/domainname or whatever fills the kernel€€€s domainname must 
 be empty or n€ 
 n-existent, as that€€€s only used for NIS/YP, which you 
 don€€€t use. (If you do, find something that works for you because I 
 have no setup of that.) This means a bare €€€domainname€€€ will return 
 €€€(none)€€€ or not echo anything (like true(1)). 
  
 I also tend to have €€€search ${fqdn#*.} [other relevant domains]€€€ 
 in /etc/resolv.conf. 
  
 This setup has fixed things like the MTA needing minutes to start 
 (or to run newaliases) because it could not resolve the hostname, 
 hostname/domain confusion, etc. It also has the benefit that the 
 canonical FQDN of the system is €€€ available at all and independent 
 of external factors, and €€€ available without having to do a DNS 
 query, which has proven massively beneficial (the short hostname 
 is of course trivially €€€cut off at the first point€€€, €€€hostname -s€€€). 
  
 I almost want to say €€€let the flames begin€€€, and Nik will likely 
 respond that he disagreed years ago with this already, but this is 
 how I run all unixoid systems (various BSDs, decades of Debian, 
 SuSE old and new, RHEL and related distros, and the occasional 
 other unixoid I ran). If this is to be revisited in Debian anyway, 
 and likely (due to the 127/8 reallocation) needs change anyway, I 
 wanted to contribute what I personally believe is the best setup. 
 As such I€€€ll not take flames (and likely not respond because I€€€m 
 not subscribed to d-devel due to the high traffic anyway). 
  
 It€€€s early enough in the release cycle that such a switch and the 
 fixing of those softwares that need a €€€cut off€€€ implemented can 
 still happen. 
  
  
 €€€ or €€€127.0.0.1 localhost localhost.localdomain€€€, though I 
   only picked up the latter€€€ on GNU systems 
 €€€ or€€€ €€€127.0.0.1 $fqdn ${fqdn%%.*} localhost localhost.localdomain€€€, 
 €€€ I currently am using the following: 
  ::1     ip6-localhost ip6-loopback localhost6 localhost6.localdomain6 
  ff02::1 ip6-allnodes 
  ff02::2 ip6-allrouters 
   I picked these up, again, mostly on GNU systems (Debian and RPM kinds) 
   and dropped bare €€€localhost€€€ from it; things currently overall tend to 
   work slightly better if €€€localhost€€€ only resolves to 127.0.0.1 and not 
   to ::1 (as well or only). Again, that €€€localhost6.localdomain6€€€ likely 
   isn€€€t needed€€€ 
 €€€ In my next overhaul of my €€€mkhosts€€€ script I€€€ll probably drop both 
 the 
   localhost.localdomain and localhost6.localdomain6; one of the 
 €€€don€€€t€€€s 
   I€€€ve seen is €€€localhost{,6}.${fqdn#*.}€€€ which is similarily useless 
 so 
   do not add that either. 
 €€€ €€€HOSTNAME=host.example.com€€€ in /etc/sysconfig/network on RHEL 
  
 So, for the above-mentioned €€€apollo€€€ system, here€€€s sample configs. 
  
 €€€€€€€€€€€€ /etc/hosts when apollo has dynamic IPs (DHCP, rtsol) only: 
 €€€ 
 €€€ 127.0.0.1 apollo.example.com apollo localhost 
 €€€ 
 €€€ ::1     ip6-localhost ip6-loopback localhost6 
 €€€ ff02::1 ip6-allnodes 
 €€€ ff02::2 ip6-allrouters 
 €€€€€€ 
  
 €€€€€€€€€€€€ /etc/hosts when apollo has static IPs: 
 €€€ 
 €€€ 127.0.0.1 localhost 
 €€€ 192.168.1.2 apollo.example.com apollo 
 €€€ 172.17.0.1 apollo.example.com apollo 
 €€€ 
 €€€ 2001:db8:0:cafe::   apollo.example.com apollo 
 €€€ 2001:db8:0:cafe::0200:5eff:fe00:5300 apollo.example.com apollo 
 €€€ 
 €€€ ::1     ip6-localhost ip6-loopback localhost6 
 €€€ ff02::1 ip6-allnodes 
 €€€ ff02::2 ip6-allrouters 
 €€€€€€ 
  
 (The example has an internal (Docker) and an external Legacy IP 
 static, an EUI64-based IP and the anycast network router.) 
  
 €€€€€€€€€€€€ /etc/hostname 
 €€€ 
 €€€ apollo.example.com 
 €€€€€€ 
  
 No /etc/domainname or an empty one. 
  
 €€€€€€€€€€€€ /etc/resolv.conf 
 €€€ 
 €€€ search example.com example.org 
 €€€ nameserver 9.9.9.9 
 €€€€€€ 
  
 $ cat /proc/sys/kernel/hostname  # Linux 
 apollo.example.com 
 $ cat /proc/sys/kernel/domainname 
 (none) 
 $ sysctl kern.{host,domain}name  # BSD 
 kern.hostname=apollo.example.com 
 kern.domainname= 
  
 Hope this helps. 
  
 bye, 
 //mirabilos 
 -- 
   €€€Having a smoking section in a restaurant is like having 
           a peeing section in a swimming pool.€€€ 
       -- Edward Burr 
  
 --- SoupGate-Win32 v1.05 
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