How to make sure docker's time syncs with that of the host?

I have dockers running on Linode servers. At times, I see that the time is not right on the dockers. Currently I have changed the run script in every docker to include the following lines of code.

yum install -y ntp
service ntpd stop
ntpdate pool.ntp.org

What I would ideally like to do however is that the docker should sync time with the host. Is there a way to do this?

Answers


The source for this answer is the comment to the answer at: Will docker container auto sync time with the host machine?

After looking at the answer, I realized that there is no way a clock drift will occur on the docker container. Docker uses the same clock as the host and the docker cannot change it. It means that doing an ntpdate inside the docker does not work.

The correct thing to do is to update the host time using ntpdate

As far as syncing timezones is concerned, -v /etc/localtime:/etc/localtime:ro works.


If you are using boot2docker and ntp doesn't work inside the docker VM (you are behind a proxy which does not forward ntp packets) but your host is time-synced, you can run the following from your host:

docker-machine ssh default "sudo date -u $(date -u +%m%d%H%M%Y)"

This way you are sending your machine's current time (in UTC timezone) as a string to set the docker VM time using date (again in UTC timezone).

NOTE: in Windows, inside a bash shell (from the msys git), use:

docker-machine.exe ssh default "sudo date -u $(date -u +%m%d%H%M%Y)"

This is what worked for me with a Fedora 20 host. I ran a container using:

docker run -v /etc/localtime:/etc/localtime:ro -i -t mattdm/fedora /bin/bash

Initially /etc/localtime was a soft link to /usr/share/zoneinfo/Asia/Kolkata which Indian Standard Time. Executing date inside the container showed me same time as that on the host. I exited from the shell and stopped the container using docker stop <container-id>.

Next, I removed this file and made it link to /usr/share/zoneinfo/Singapore for testing purpose. Host time was set to Singapore time zone. And then did docker start <container-id>. Then accessed its shell again using nsenter and found that time was now set to Singapore time zone.

docker start <container-id>
docker inspect -f {{.State.Pid}} <container-id>
nsenter -m -u -i -n -p -t <PID> /bin/bash

So the key here is to use -v /etc/localtime:/etc/localtime:ro when you run the container first time. I found it on this link.

Hope it helps.


You can add your local files (/etc/timezone and /etc/localtime) as volume in your docker-container.

Update your docker-compose.yml with the following lines.

volumes:
    - "/etc/timezone:/etc/timezone:ro"
    - "/etc/localtime:/etc/localtime:ro"

Now the container time is the same as on your host


If you're using docker-machine, the virtual machines can drift. To update the clock on the virtual machine without restarting run:

docker-machine ssh <machine-name|default>
sudo ntpclient -s -h pool.ntp.org

This will update the clock on the virtual machine using NTP and then all the containers launched will have the correct date.


I was facing a time offset of -1hour and 4min

Restarting Docker itself fixed the issue for me.

To set the timezone in general:

  1. ssh into your container: docker exec -it my_website_name bash

  2. run dpkg-reconfigure tzdata

  3. run date

It appears there can by time drift if you're using Docker Machine, as this response suggests: https://stackoverflow.com/a/26454059/105562 , due to VirtualBox.

Quick and easy fix is to just restart your VM:

docker-machine restart default

For docker on macOS, you can use docker-time-sync-agent. It works for me.


I have the following in the compose file

volumes:
  - "/etc/timezone:/etc/timezone:ro"
  - "/etc/localtime:/etc/localtime:ro"

Then all good in Gerrit docker with its replication_log set w/ correct timestamp. :-D


With docker for windows I had to tick

MobyLinuxVM > Settings > Integration Services > Time synchronization 

in Hyper-V manager and it worked


docker-compose usage:

Add /etc/localtime:/etc/localtime:ro to the volumes attribute:

version: '3'

services:
  a-service:
      build: .
      image: service-name
      container_name: container-name
      volumes:
        - /etc/localtime:/etc/localtime:ro

This will reset the time in the docker server:

docker run --rm --privileged alpine hwclock -s

Next time you create a container the clock should be correct.

Source: https://github.com/docker/for-mac/issues/2076#issuecomment-353749995


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