Hi,
I'm currently fiddling with Docker Swarm on three sandbox servers running CentOS 7.
Unfortunately I couldn't get even the most basic configuration running. After some experimenting and investigating, it turns out there's a problem with FirewallD.
Here's what I did first on every single node.
# firewall-cmd --permanent --add-service=docker-swarm # firewall-cmd --reload
I launched a simple web service like this:
# docker service create --name web -p 80:80 nginx
My three nodes appear correctly with 'docker node ls'.
From here, I should be able to open the Nginx default web page in a web browser
using any node's hostname.
But nothing happens. No page is loaded.
On a whim, I turned off FirewallD, and suddenly everything worked as expected.
Now here's the list of ports that have to be open on every single node for Docker Swarm to work:
* 2376/tcp * 2377/tcp * 7946/tcp * 7946/udp * 4789/udp
And here's what docker-swarm.xml looks like under CentOS 7:
# cat /usr/lib/firewalld/services/docker-swarm.xml <?xml version="1.0" encoding="utf-8"?> <service> <short>Docker integrated swarm mode</short> <description>Natively managed cluster of Docker Engines (>=1.12.0), where you deploy services.</description> <port port="2377" protocol="tcp"/> <port port="7946" protocol="tcp"/> <port port="7946" protocol="udp"/> <port port="4789" protocol="udp"/> <protocol value="esp"/> </service>
So it looks like TCP port 2376 was forgotten in that service definition.
I opened it up manually on every node:
# firewall-cmd --permanent --add-port=2376/tcp # firewall-cmd --reload
And now Docker Swarm works correctly.
Cheers from the sunny South of France,
Niki Kovacs
Who packaged this docker swarm thing?
On Thu, Aug 13, 2020, 1:27 AM Nicolas Kovacs info@microlinux.fr wrote:
Hi,
I'm currently fiddling with Docker Swarm on three sandbox servers running CentOS 7.
Unfortunately I couldn't get even the most basic configuration running. After some experimenting and investigating, it turns out there's a problem with FirewallD.
Here's what I did first on every single node.
# firewall-cmd --permanent --add-service=docker-swarm # firewall-cmd --reload
I launched a simple web service like this:
# docker service create --name web -p 80:80 nginx
My three nodes appear correctly with 'docker node ls'.
From here, I should be able to open the Nginx default web page in a web browser using any node's hostname.
But nothing happens. No page is loaded.
On a whim, I turned off FirewallD, and suddenly everything worked as expected.
Now here's the list of ports that have to be open on every single node for Docker Swarm to work:
- 2376/tcp
- 2377/tcp
- 7946/tcp
- 7946/udp
- 4789/udp
And here's what docker-swarm.xml looks like under CentOS 7:
# cat /usr/lib/firewalld/services/docker-swarm.xml
<?xml version="1.0" encoding="utf-8"?>
<service> <short>Docker integrated swarm mode</short> <description>Natively managed cluster of Docker Engines (>=1.12.0), where you deploy services.</description> <port port="2377" protocol="tcp"/> <port port="7946" protocol="tcp"/> <port port="7946" protocol="udp"/> <port port="4789" protocol="udp"/> <protocol value="esp"/> </service>
So it looks like TCP port 2376 was forgotten in that service definition.
I opened it up manually on every node:
# firewall-cmd --permanent --add-port=2376/tcp # firewall-cmd --reload
And now Docker Swarm works correctly.
Cheers from the sunny South of France,
Niki Kovacs
-- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info@microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12 _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
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