[Users] No FQDN hostname for COS7/RHEL7 containers?

[Sabine Jordan]

Helle Scott,

I know that rhel6 has no /etc/hostname and it was not my question unless you wanted to explain that we should not run rhel7/cos7 containers on rhel6 based openvz kernel hardware node.
It works as expected, if I remove the lines from the script "/etc/vz/dists/scripts/redhat-set_hostname.sh" where the /etc/hostname of the container is changed...

Greetings, Sabine


> Am 05.08.2015 um 17:51 schrieb Scott Dowdle <dowdle at montanalinux.org>:
> 
> Greetings,
> 
> ----- Original Message -----
>> Dear OpenVZ users,
>> 
>> I've got a questions concerning RHE7/CENTOS7 containers and the
>> change in the script "/etc/vz/dists/scripts/redhat-set_hostname.sh"
>> which comes with the newer versions of vzctl-core...
>> 
>> function set_hostname()
>> {
>>   local cfgfile="$1"
>>   local var=$2
>>   local val=$3
>> 
>>   [ -z "${val}" ] && return 0
>> 
>>   if [ -f /etc/hostname ]; then
>>       # New style: RHEL7/Fedora15+
>>       # Note hostname(5) says it should NOT be FQDN
>>   val=${val%%.*}
>>       echo "$val" > /etc/hostname
>>   else
>>       # "Classic" style
>>       put_param "${cfgfile}" "${var}" "${val}"
>>   fi
>> 
>>   hostname "${val}"
>> }
>> 
>> change_hostname /etc/hosts "${HOSTNM}" "${IP_ADDR}"
>> 
>> 
>> We've got some CENTOS7 containers for testing (running on Hardware
>> with rhel6 openvz kernel at the moment) The hostname which should be
>> FQDN in our environment is set to short hostname all the time. This
>> happens because the file/etc/hostname exists in Centos 7.
>> 
>> The redhat-set_hostname.sh script changes our entry /etc/hostname  to
>> short hostname...
>> 
>> When I read the man pages of my COS 7.1.1503 Container, I don't see
>> any entry saying that hostname should not be FQDN....
>> 
>> Hostname(5) says that it is recommended but, not that it is a strict
>> requirement...
>> 
>> DESCRIPTION
>>      The /etc/hostname file configures the name of the local system
>>      that is set during boot using the sethostname(2) system call.
>>      It should contain a single newline-terminated hostname string.
>>      The
>>      hostname may be a free-form string up to 64 characters in
>>      length; however, it is recommended that it consists only of
>>      7-bit ASCII lower-case characters and no spaces or dots, and
>>      limits itself to
>>      the format allowed for DNS domain name labels, even though this
>>      is not a strict requirement.
>> 
>> Hostname(1) says the following...
>> 
>> FILES
>>      /etc/hostname  Historically  this  file  was supposed to only
>>      contain the hostname and not the full canonical FQDN. Nowadays
>>      most software is able to cope with a full FQDN here. This file
>>      is read at
>>      boot time by the system initialization scripts to set the
>>      hostname.
>> 
>> So why do you prevent users from setting their hostname to
>> fqdn-hostname with the change of the script above?
> 
> I have a RHEL6 physical host and it does not have an /etc/hostname file.  Where does the system get its hostname from then?  From /etc/sysconfig/network with a HOSTNAME= line and yes the FQDN is in there.
> 
> On RHEL7 it is different.  systemd provides a tool for setting the hostname (hostnamectl which stores the FQDN in /etc/hostname) and typically (on a physical host anyway) NetworkManager is used.  Since EL7 containers don't use NetworkManager, putting the hostname in /etc/sysconfig/network and/or /etc/hostname should work.  In fact shortly after CentOS 7.0 OS Template as released I filed a bug because hostnamectl putting it in /etc/hostname was being ignored so they fixed that.
> 
> So to answer your question, EL6 doesn't use /etc/hostname.
> 
> TYL,
> -- 
> Scott Dowdle
> 704 Church Street
> Belgrade, MT 59714
> (406)388-0827 [home]
> (406)994-3931 [work]
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