CentOS virt - Jan 2016 - Hostname inside lxc container

Hi all,

 I have installed a CentOS6 lxc guest under a Debian 8.x LXC host. All
it is working ok but I can't change the hostname for the centos6 lxc
container (it is using the same hostname from Debian host). I have
modifyed HOSTNAME under /etc/sysconfig/network and /etc/hosts file,
but it doesn't works.

 Do I need to change anything else??

Thanks.

Greetings,

----- Original Message -----
> I have installed a CentOS6 lxc guest under a Debian 8.x LXC host.
> All it is working ok but I can't change the hostname for the centos6
lxc
> container (it is using the same hostname from Debian host). I have
> modifyed HOSTNAME under /etc/sysconfig/network and /etc/hosts file,
> but it doesn't works.
> 
> Do I need to change anything else??
If I remember correctly, it is generally set in /etc/sysconfig/network on a
regular EL6 host.  If that isn't working when run within an LXC container on
a Debian host... ask whoever packaged up the LXC container template you used. 
There is a lot of variance in LXC from one distro to another.  Some recipes say
to install from a .tar.gz file (which I prefer to call an OS Template) others
say to do a chroot install using a distro's native package manager.  My
point is, that LXC tools and methods really vary... and I don't think the
CentOS project can help much in this situation.

For containers, I've been using OpenVZ (now called OpenVZ Legacy while they
work on the newer Virtuozzo 7) for 10 years now... and they have a standard set
of OS Templates for a range of distros and everything (generally) works as it is
supposed to... and even with that... the CentOS Project isn't interested in
helping OpenVZ users running CentOS containers... because it uses a non-CentOS
provided kernel and management tools... although the recommended OpenVZ Legacy
hostnode distro is CentOS 6.x.  Virtuozzo 7 is its own distro rebased from
CentOS 7.

One container technology they are interested in supporting is Docker (app
containers) especially when using the official CentOS Docker images
built/provided by the CentOS Project... running on a CentOS host.

TYL,
-- 
Scott Dowdle
704 Church Street
Belgrade, MT 59714
(406)388-0827 [home]
(406)994-3931 [work]

On 21.01.2016 15:44, C. L. Martinez wrote:
> Hi all,
> 
>  I have installed a CentOS6 lxc guest under a Debian 8.x LXC host. All
> it is working ok but I can't change the hostname for the centos6 lxc
> container (it is using the same hostname from Debian host). I have
> modifyed HOSTNAME under /etc/sysconfig/network and /etc/hosts file,
> but it doesn't works.
> 
>  Do I need to change anything else??
These Files only persist the hostname. To actually set it live you have
to call "hostname <hostname>". Your shell prompt will not change
unless
you log out and log in again though simply executing "hostname"
without
parameters should output the correct name right away.

Keep in mind though that setting the hostname in a container requires
explicit support for the UTS namespace on the host:

http://man7.org/linux/man-pages/man7/namespaces.7.html

If the host doesn't support the UTS namespace for its guests or this
feature is not configured for the guest in question then setting the
hostname in the guest is not possible.

Regards,
  Dennis

On Thu, Jan 21, 2016 at 6:25 PM, Dennis Jacobfeuerborn
<dennisml at conversis.de> wrote:
> On 21.01.2016 15:44, C. L. Martinez wrote:
>> Hi all,
>>
>>  I have installed a CentOS6 lxc guest under a Debian 8.x LXC host. All
>> it is working ok but I can't change the hostname for the centos6
lxc
>> container (it is using the same hostname from Debian host). I have
>> modifyed HOSTNAME under /etc/sysconfig/network and /etc/hosts file,
>> but it doesn't works.
>>
>>  Do I need to change anything else??
>
> These Files only persist the hostname. To actually set it live you have
> to call "hostname <hostname>". Your shell prompt will not
change unless
> you log out and log in again though simply executing "hostname"
without
> parameters should output the correct name right away.
>
> Keep in mind though that setting the hostname in a container requires
> explicit support for the UTS namespace on the host:
>
> http://man7.org/linux/man-pages/man7/namespaces.7.html
>
> If the host doesn't support the UTS namespace for its guests or this
> feature is not configured for the guest in question then setting the
> hostname in the guest is not possible.
>
> Regards,

Thanks Dennis. I have tried to fix using "hostname" command but after
reboot, returns to be the same hostname as Debian host. Debian kernel
has UTS enabled ...