[CentOS] Short or long hostname ?

[Simon Matter]

>
>
> On 4/10/19 8:23 AM, Simon Matter via CentOS wrote:
>>> Hi,
>>>
>>> For the last ten years or so, I've defined the short hostname in
>>> /etc/hostname and the FQDN in /etc/hosts. Now I wanted to double-check
>>> this information, which eventually led me to this page:
>>>
>>>    *
>>> https://serverfault.com/questions/331936/setting-the-hostname-fqdn-or-short-name
>>>
>>> Now I admit I'm even more confused than before.
>>>
>>> Is there some reliable piece of information on this subject for CentOS
>>> ?
>>
>> IMHO for those having proper DNS in place, the hostname should be set to
>> the FQDN in whatever place it is supposed to be set. I quite feel there
>> is
>> something wrong if the only place where the FQDN is listed is the
>> /etc/hosts file.
>>
>> I'm not very happy with how the issue was handled in Linux and the
>> different distributions in the last decades. Not to mention the
>> inconsistency in the relevant man pages.
>
> Well, I am unhappy for about as long about /etc/hosts and how name
> resolution "should" happen which it doesn't, namely, if
> /etc/nsswitch.conf says
>
> hosts: files dns
>
> then ideally /etc/hosts should be used first, then nameservers. However
> (and this is true both for Linux and FreeBSD), some commands never look
> into /etc/hosts (e.g., command host), whereas some do use /etc/hosts
> (e.g., command ping).

Well, in case of the host command it seems clear that it doesn't look up
/etc/hosts as it is a "DNS lookup utility", as the man page states, and
not a general name resolution utility. I had to learn this, guess how.

But all in all it's a bit of a mess, yes. Unfortunately I'm tempted to
expect that systemd-resolved will even make it worse :-)

Regards,
Simon

>
> Valeri
>
>>
>> I found the info mentioned in the FreeBSD man pages quite helpful even
>> if
>> it has to be "translated" to Linux. See the excerpt of the mentioned man
>> pages below. If you believe this is heresy to be posted here, please
>> don't
>> read it :-)
>>
>> Regards,
>> Simon
>>
>> ----%>-------------------------------
>> root at freebsd:~ # man hostname
>> HOSTNAME(1)             FreeBSD General Commands Manual
>> HOSTNAME(1)
>>
>> NAME
>>       hostname - set or print name of current host system
>>
>> SYNOPSIS
>>       hostname [-f] [-s | -d] [name-of-host]
>>
>> DESCRIPTION
>>       The hostname utility prints the name of the current host.  The
>> super-user
>>       can set the hostname by supplying an argument; this is usually
>> done in
>>       the initialization script /etc/rc.d/hostname, normally run at boot
>> time.
>>       This script uses the hostname variable in /etc/rc.conf.
>> ...
>>
>>
>> root at freebsd:~ # man rc.conf
>> RC.CONF(5)                FreeBSD File Formats Manual
>> RC.CONF(5)
>>
>> NAME
>>       rc.conf - system configuration information
>>
>> DESCRIPTION
>>       The file rc.conf contains descriptive information about the local
>> host
>> ...
>>       hostname (str) The fully qualified domain name (FQDN) of this host
>> on
>>                the network.  This should almost certainly be set to
>>                something meaningful, even if there is no network
>> connection.
>>                If dhclient(8) is used to set the hostname via DHCP, this
>>                variable should be set to an empty string.  Within a
>> jail(8)
>>                the hostname is generally already set and this variable
>> may
>>                absent.  If this value remains unset when the system is
>> done
>>                booting your console login will display the default
>> hostname
>>                of "Amnesiac".
>>
>> _______________________________________________
>> CentOS mailing list
>> CentOS at centos.org
>> https://lists.centos.org/mailman/listinfo/centos
>>
>
> --
> ++++++++++++++++++++++++++++++++++++++++
> Valeri Galtsev
> Sr System Administrator
> Department of Astronomy and Astrophysics
> Kavli Institute for Cosmological Physics
> University of Chicago
> Phone: 773-702-4247
> ++++++++++++++++++++++++++++++++++++++++
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