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-...

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).

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@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@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".

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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-...

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.

It's my impression that trying to resolve a host on a Linux system (and also other *nix like systems) is best done with the getent utility:

getent hosts <hostname>

It shows what other programs see as well.

Regards, Simon