[ovirt-users] chrony or ntp ?

[Michal Skrivanek]

> On 9 Jun 2017, at 11:46, Sandro Bonazzola <sbonazzo at redhat.com> wrote:
> 
> 
> 
> On Fri, Jun 9, 2017 at 11:05 AM, Fabrice Bacchella <fabrice.bacchella at orange.fr <mailto:fabrice.bacchella at orange.fr>> wrote:
> I haven't switched from ntp to chrony. So I have configured my puppet to remove it as it's now part of default installation of rhel.
> 
> I works well with everything except on vdsm, since last upgrade:
> 
>  # yum erase chrony
> ..
> Removing for dependencies:
>  vdsm                                              x86_64                               4.19.15-1.el7.centos                               @ovirt-4.1                               2.6 M
>  vdsm-hook-vmfex-dev                               noarch                               4.19.15-1.el7.centos                               @ovirt-4.1                                21 k
> 
> 
> Why vdsm depends on chrony ? Any time synchronisation solution is good. Is that the role of ovirt to chose for me ?
> 
> Adding people involved in this change.
> Please note the change has been reviewed and discussed on https://gerrit.ovirt.org/#/c/73822/ <https://gerrit.ovirt.org/#/c/73822/> for addressing https://bugzilla.redhat.com/show_bug.cgi?id=1428419 <https://bugzilla.redhat.com/show_bug.cgi?id=1428419>
> and it moves from requiring ntp to requiring chrony.
> So it was already deciding for you, you just both were in agreement :-)
> 
> Sadly:
> # rpm -q --provides ntp
> config(ntp) = 4.2.8p10-1.fc26
> ntp = 4.2.8p10-1.fc26
> ntp(x86-64) = 4.2.8p10-1.fc26
> 
> rpm -q --provides chrony
> chrony = 3.1-4.fc26
> chrony(x86-64) = 3.1-4.fc26
> config(chrony) = 3.1-4.fc26
> 
> there's no way to require just the time synchronization capability like in httpd providing the webserver capability:
> 
> # rpm -q --provides httpd
> config(httpd) = 2.4.25-8.fc26
> httpd = 2.4.25-8.fc26
> httpd(x86-64) = 2.4.25-8.fc26
> httpd-mmn = 20120211
> httpd-mmn = 20120211x8664
> httpd-suexec = 2.4.25-8.fc26
> mod_dav = 2.4.25-8.fc26
> webserver
> 
> # dnf provides webserver
> Ultima verifica della scadenza dei metadati: 0:02:59 fa il Fri Jun 09 11:36:58 2017 CEST.
> httpd-2.4.25-8.fc26.x86_64 : Apache HTTP Server
> Repo         : @System
> 
> nginx-1:1.10.3-1.fc26.x86_64 : A high performance web server and reverse proxy server
> Repo         : @System
> 
> httpd-2.4.25-8.fc26.x86_64 : Apache HTTP Server
> Repo         : updates-testing
> 
> cherokee-1.2.104-1.fc25.i686 : Flexible and Fast Webserver
> Repo         : fedora
> 
> cherokee-1.2.104-1.fc25.x86_64 : Flexible and Fast Webserver
> Repo         : fedora
> 
> httpd-2.4.25-5.fc26.x86_64 : Apache HTTP Server
> Repo         : fedora
> 
> lighttpd-1.4.45-3.fc26.x86_64 : Lightning fast webserver with light system requirements
> Repo         : fedora
> 
> nginx-1:1.10.3-1.fc26.x86_64 : A high performance web server and reverse proxy server
> Repo         : fedora
> 
> In Fedora we may use boolean dependencies and install chrony only if ntp is not already installed: http://rpm.org/user_doc/boolean_dependencies.html <http://rpm.org/user_doc/boolean_dependencies.html>
> but this feature is not available in RHEL / CentOS.
> 
> I let others explain why we are enforcing the dependency on the package itself instead of moving vdsm to an error state if time synchronization is disabled at runtime:

because it’s much more problematic to troubleshoot and fix then.
The main reason is by enforcing NTP service on the host we get a good time sync even for people who do not care/do not know anything about it and get the right setup from DHCP
As Sandro says there is no easy way to identify the capability in general, and chrony is the default in el7

You can just disable the chrony service(we rely on the fact it’s enabled by default) and install any other NTP service as you prefer

Thanks,
micahl

> 
> # timedatectl status
>       Local time: ven 2017-06-09 11:45:18 CEST
>   Universal time: ven 2017-06-09 09:45:18 UTC
>         RTC time: ven 2017-06-09 09:45:18
>        Time zone: Europe/Rome (CEST, +0200)
>  Network time on: yes
> NTP synchronized: yes
>  RTC in local TZ: no
> 
> # rpm -qf `which timedatectl`
> systemd-233-3.fc26.x86_64
> 
> 
>  
> 
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> 
> -- 
> SANDRO BONAZZOLA
> ASSOCIATE MANAGER, SOFTWARE ENGINEERING, EMEA ENG VIRTUALIZATION R&D
> Red Hat EMEA <https://www.redhat.com/>
>  <https://red.ht/sig>	
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