docker swarm how to find out why service can't start

Question

I often have problems because a service that I deploy on docker swarm with multiple nodes won't start and there are not logs generated that I can look at with docker service logs {serviceName}

There are many possible reasons for a service not to start such as

• Can't download image from registry
• Constraints that can't be fulfilled

I have trouble finding out why a container won't start. I found the command docker service ps {serviceName} which List the tasks of one or more services and a short error message (if there was an error). However when I try to inspect the task with docker service logs {taskId} (which should show logs of a task) I get Error response from daemon: task 3lkgo8t2sn7k not found.

Can anyone help me get a full error message why a service won't start?

Answer 1

I found one handy solution to the problem.

docker service ps --no-trunc {serviceName} 

which will show errors with downloading images, mounting nfs volumes amongst others.

---------------------- UPDATE

Not all errors can be found in the way described above. Another usefull tool is looking at the docker deamon logs which can be done the follwing way as explained on stackoverflow:

journalctl -u docker.service | tail -n 50  

It depends on your OS. Here are the few locations, with commands for few Operating Systems:

• Ubuntu (old using upstart ) - /var/log/upstart/docker.log
• Ubuntu (new using systemd ) - journalctl -u docker.service
• Boot2Docker - /var/log/docker.log
• Debian GNU/Linux - /var/log/daemon.log
• CentOS - /var/log/daemon.log | grep docker
• CoreOS - journalctl -u docker.service
• Fedora - journalctl -u docker.service
• Red Hat Enterprise Linux Server - /var/log/messages | grep docker
• OpenSuSE - journalctl -u docker.service
• OSX - ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/log/d‌​ocker.log
• Windows - Get-EventLog -LogName Application -Source Docker -After (Get-Date).AddMinutes(-5) | Sort-Object Time, as mentioned here.