Is there an option to show, that metadata.google.internal
is used as NTP when i connect to a pod or to the kubernetes VM?
I tried the following: ntpq -p
, which results in command not found, but was listed on https://cloud.google.com/compute/docs/instances/managing-instances. This file does not exist: vim /etc/ntp.conf
. I need that as a proof, showing which server is used.
![](../../users/profiles/563118.webp)
- 121
- 2
-
1Are you using `Container-Optimized OS` in your GKE cluster? – Dawid Kruk Mar 09 '20 at 09:35
-
One workaround would be to go for pod with package manager, install nslookup on it and check `$ nslookup metadata.google.internal`. It should give the IP address of `169.254.169.254`. After that you can check `systemctl status systemd-timesyncd.service` and specifically the part of `Synchronized to time server`. – Dawid Kruk Mar 09 '20 at 15:15
1 Answers
When you create a GKE cluster you have an option to specify which operating system will be the base for your Kubernetes installation. You have the options to choose from:
- Container-Optimized OS (cos)
- Container-Optimized OS (cos) with containerd
- Ubuntu
- Ubuntu with containerd
You can choose it by following a path in Google Cloud Platform:
Kubernetes Engine -> Create a Kubernetes cluster -> Node-pools -> default-pool -> Nodes -> Image type.
What you choose will affect what tools you will be able to use internally on the nodes.
Container-Optimized OS
A word about Container-Optimized OS:
Container-Optimized OS is an operating system image for your Compute Engine VMs that is optimized for running Docker containers. With Container-Optimized OS, you can bring up your Docker containers on Google Cloud Platform quickly, efficiently, and securely. Container-Optimized OS is maintained by Google and is based on the open source Chromium OS project.
Please take a look on official documentation talking about features, benefits and limitations of Container-Optimized OS: Cloud.google.com: Container-optimized OS features,benefits and limitations
Container-Optimized OS does not include a package manager; as such, you'll be unable to install software packages directly on an instance. However, you can use CoreOS toolbox to install and run debugging and admin tools in an isolated container.
As said in above documentation there is no package manager available but you can use CoreOS toolbox to debug and install required software.
You can check which server is used by your Container-Optimized OS node with systemd as follows:
$ systemctl status systemd-timesyncd
It should give you an output similar to this:
● systemd-timesyncd.service - Network Time Synchronization
Loaded: loaded (/usr/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: disabled)
Active: active (running) since Tue 2020-03-03 21:17:35 UTC; 6 days ago
Docs: man:systemd-timesyncd.service(8)
Main PID: 219 (systemd-timesyn)
Status: "Synchronized to time server 169.254.169.254:123 (169.254.169.254)."
Tasks: 2 (limit: 4915)
Memory: 832.0K
CPU: 591ms
CGroup: /system.slice/systemd-timesyncd.service
└─219 /usr/lib/systemd/systemd-timesyncd
Please take a specific look on
Status: "Synchronized to time server 169.254.169.254:123 (169.254.169.254)."
Above message indicates which server is used by node to synchronize time.
You can get more information about IP address of 169.254.169.254
by following: Serverfault.com: What is this IP address 169.254.169.254
You can check the DNS name of 169.254.169.254
with mentioned CoreOS Toolbox on your node and nslookup
:
$ /usr/bin/toolbox
$ apt-get install -y dnsutils
$ nslookup 169.254.169.254
It should give you an output:
Server: 169.254.169.254
Address: 169.254.169.254#53
Non-authoritative answer:
254.169.254.169.in-addr.arpa name = metadata.google.internal.
Authoritative answers can be found from:
Above output indicates that the address of 169.254.169.254
is the mentioned metadata.google.internal
Ubuntu
With GKE cluster created with Ubuntu image you check NTP information with:
- systemd
- dhcp lease
ntptrace
nslookup
Systemd
You can check which NTP server is used by your Ubuntu node the same as with Container-Optimized OS as follows:
$ systemctl status systemd-timesyncd
DHCP lease
The DHCP lease contains information about NTP server. You can get information about DHCP lease as follows:
USER@NODE:~$ cat /var/lib/dhcp/dhclient.leases
Output of above command should look like below:
lease {
interface "eth0";
fixed-address 10.156.0.X;
option subnet-mask 255.255.255.255;
option routers 10.156.0.1;
option dhcp-lease-time 86400;
option dhcp-message-type 5;
option domain-name-servers 169.254.169.254;
option dhcp-server-identifier 169.254.169.254;
option interface-mtu 1460;
option domain-search "X.internal.", "Y.internal";
option ntp-servers 169.254.169.254;
option rfc3442-classless-static-routes 32,10,156,0,1,0,0,0,0,0,10,156,0,1;
option host-name "X.internal";
option domain-name "X.internal";
renew 2 2020/03/10 09:12:37;
rebind 2 2020/03/10 18:40:09;
expire 2 2020/03/10 21:40:09;
}
Please take a specific look on:
option ntp-servers 169.254.169.254;
This line indicates the NTP server used.
Ntptrace
Ntptrace
should show 169.254.169.254
as follows:
localhost: stratum 3, offset 0.000058, synch distance 0.026242
169.254.169.254: timed out, nothing received
***Request timed out
Nslookup
You can check the ntp-server
with nslookup
in the same manner as in CoreOS Toolbox if it matches the metadata.google.internal
.
Please let me know if you have any questions in this topic.
![](../../users/profiles/545585.webp)
- 588
- 2
- 8