Chrony on Cumulus Linux

On ARM-based platforms running Cumulus Linux 4.3.0, you can use Chrony as the time provider.

To use Chrony, you need to:

  • Edit the /etc/apt/sources.list file to allow upstream repositories.
  • Update the local index from source with the apt command-line utility.
  • Remove and purge NTP with the apt command-line utility.
  • Install Chrony.
  • Edit the system configuration to establish Chrony as a management service.
  • Add a low latency time source to the Chrony configuration.

NVIDIA has validated the following procedure with Netq 4.2.0 (4.2.0-cl4u38~1652820696.25f4ac06) and chrony_3.4-4+deb10u2_armel.deb.

  1. Edit the /etc/apt/sources.list file to allow upstream repositories:

    root@cumulus:mgmt:/home/cumulus# sudo vi /etc/apt/sources.list
    # Cumulus Linux package repository
    deb CumulusLinux-4-latest cumulus upstream netq
    deb-src CumulusLinux-4-latest cumulus upstream netq
    # NetQ package repository
    deb CumulusLinux-4 netq-latest
    # Debian 10 Buster main package repositories
    # Uncomment these if you want to install upstream Debian packages
    # that are not mirrored in the Cumulus Linux repositories.
    # Packages installed this way may cause problems, and are not
    # officially supported by Cumulus Networks, Inc.
    deb buster main
    deb buster-updates main
    deb buster/updates main
    deb buster-backports main
    # Debian 10 Buster main package source repositories
    # Only need to uncomment these if you want to install
    # upstream Debian source packages
    #deb-src buster main
    #deb-src buster-updates main
    #deb-src buster/updates main
    #deb-src buster-backports main
  2. Update the local index from source:

    root@cumulus:mgmt:/home/cumulus# sudo -E apt-get update
  3. Remove and purge NTP from the system:

    root@cumulus:mgmt:/home/cumulus# sudo -E apt-get -y purge --auto-remove ntp
  4. Install Chrony:

    root@cumulus:mgmt:/home/cumulus# sudo -E apt-get -y install chrony
  5. Add Chrony as a management VRF service to the system startup configuration in the /etc/vrf/systemd.conf file:

    root@cumulus:mgmt:/home/cumulus# sudo vi /etc/vrf/systemd.conf
    # Systemd-based services that are expected to be run in a VRF context.
    # If changes are made to this file run systemctl daemon-reload
    # to re-generate systemd files.
    chrony <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    root@cumulus:mgmt:/home/cumulus# systemctl stop chronyd
    root@cumulus:mgmt:/home/cumulus# systemctl disable chronyd
    root@cumulus:mgmt:/home/cumulus# systemctl enable chrony@mgmt
    root@cumulus:mgmt:/home/cumulus# systemctl restart chrony@mgmt
    root@cumulus:mgmt:/home/cumulus# systemctl daemon-reload
  6. For optimal performance, add a low latency time source /etc/chrony/chrony.conf configuration file. Use the chronyc sources -v syntax to verify the configuration.

    root@cumulus:mgmt:/home/cumulus# chronyc sources -v
    210 Number of sources = 1
      .-- Source mode  '^' = server, '=' = peer, '#' = local clock.
     / .- Source state '*' = current synced, '+' = combined , '-' = not combined,
    | /   '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
    ||                                                 .- xxxx [ yyyy ] +/- zzzz
    ||      Reachability register (octal) -.           |  xxxx = adjusted offset,
    ||      Log2(Polling interval) --.      |          |  yyyy = measured offset,
    ||                                \     |          |  zzzz = estimated error.
    ||                                 |    |           \
    MS Name/IP address         Stratum Poll Reach LastRx Last sample
    ^* master_source.local.>     2   6    77     6  -1102us[ -108ms] +/- 2754us

For information about Chrony, refer to the Chrony project page.