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Enable TCP port 2375 for external connection to Docker
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docker-api-port.md

Enable TCP port 2375 for external connection to Docker

See this issue.
Docker best practise to Control and configure Docker with systemd.

  1. Create daemon.json file in /etc/docker:

     {"hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]}

  2. Add /etc/systemd/system/docker.service.d/override.conf

     [Service]
 ExecStart=
 ExecStart=/usr/bin/dockerd

  3. Reload the systemd daemon:

     systemctl daemon-reload

  4. Restart docker:

     systemctl restart docker.service
@Sharaf5
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Sharaf5 commented Dec 9, 2022 •
edited
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Another thing to think about is security

Is the exposed port with your methods are encrypted or not ?

docker:dind has two ports to expose

  • 2375 no encrypton - context do not require cert or key
  • 2376 encrypted - context require key pair to qualify connection

Is that encryption applicable with your methods ?

I think this is the part where we go inside docker:dind entry point file
code

so it should be this part

dockerd \
     --host="$dockerSocket" \
     --host=tcp://0.0.0.0:2376 \
     --tlsverify \
     --tlscacert "$DOCKER_TLS_CERTDIR/server/ca.pem" \
     --tlscert "$DOCKER_TLS_CERTDIR/server/cert.pem" \
     --tlskey "$DOCKER_TLS_CERTDIR/server/key.pem"

and @russellhoff : you are right

  • the daemon server is running but as an entrypoint and not a service (I miss understood)

@abel-delafuente
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abel-delafuente commented Dec 29, 2022 •
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When i try to build the image be means of the BuildImage command, i am getting the

Connect to http://127.0.0.1:2375 [/127.0.0.1] failed: Connection refused: no further information

Apparently Gradle does not make match with the WSL platform IP.

@lalalazero
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lalalazero commented Jan 9, 2023

thanks a lot

@KMMehr
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KMMehr commented Jan 14, 2023

Great job
Thanks

@Sharaf5
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Sharaf5 commented Jan 14, 2023

@abel-delafuente tcp not http
you could also try to use a unix socket instead and test again to make sure if it's a docker behavior or a network restriction

@KyongSik-Yoon
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KyongSik-Yoon commented Apr 27, 2023

Great! It's working for me.

@djshaw0350
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djshaw0350 commented Jul 18, 2023

Anyone having issues on DietPi? I am just getting familiar with DietPi and cannot get this to work.

@intellectualDarknet
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intellectualDarknet commented Jul 31, 2023

that helped thank you!

@lennon101
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lennon101 commented Sep 12, 2023

Add /etc/systemd/system/docker.service.d/override.conf
[Service]
ExecStart=
ExecStart=/usr/bin/dockerd

I'm on a Synology NAS and I don't have the folder /etc/systemd/system/docker.service.d/override.conf ??? Any help on how to do step 2?

@My-Random-Thoughts
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My-Random-Thoughts commented Sep 19, 2023

For everyone finding this page and looking for instructions for Synology's new Container Manager,

  1. sudo vi /var/packages/ContainerManager/etc/dockerd.json

change to:
{"data-root":"/var/packages/ContainerManager/var/docker","log-driver":"db","registry-mirrors":[],"storage-driver":"aufs","hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]}

(basically add the stuff from the original step 1 to the end, without the curly-brackets {} )

  1. systemctl daemon-reload

  2. sudo systemctl restart pkg-ContainerManager-dockerd

You may need to repeat these steps when the Container Manager package gets updated. So far it's working for me

@honue
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honue commented Sep 20, 2023

For everyone finding this page and looking for instructions for Synology's new Container Manager,

  1. sudo vi /var/packages/ContainerManager/etc/dockerd.json

change to: {"data-root":"/var/packages/ContainerManager/var/docker","log-driver":"db","registry-mirrors":[],"storage-driver":"aufs","hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]}

(basically add the stuff from the original step 1 to the end, without the curly-brackets {} )

  1. systemctl daemon-reload
  2. sudo systemctl restart pkg-ContainerManager-dockerd

You may need to repeat these steps when the Container Manager package gets updated. So far it's working for me

Hi,bro. I'm trying to add the proxy option for the dockerd.json,there is some problem for me.
I had read the docs of how to set the value of daemon-proxy,but the error still exsit.

  "proxies": {
    "http-proxy": "http://proxy.example.com:80",
    "https-proxy": "https://proxy.example.com:443",
    "no-proxy": "*.test.example.com,.example.org",
  }

unable to configure the Docker daemon with file /var/packages/ContainerManager/etc/dockerd.json: the following directives don't match any configuration option: http-proxy, https-proxy, no-proxy

{"data-root":"/var/packages/ContainerManager/var/docker","log-driver":"db","proxies":{"http-proxy":"http://127.0.0.1:7890","https-proxy":"http://127.0.0.1:7890","no-proxy":"localhost,127.0.0.1"},"registry-mirrors":[],"storage-driver":"aufs"}
can you give me some help? appreciate it.

@My-Random-Thoughts
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My-Random-Thoughts commented Sep 20, 2023

Sorry @honue , I don't know as I don't use proxies. Maybe Synology doesn't support those options. They are also using a slightly older version of docker. v20.10.23, build 876964a

@solarsparq
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solarsparq commented Oct 26, 2023

ExecStart=
ExecStart=/usr/bin/dockerd --config-file /etc/docker/daemon.json

Thank you. This override.conf trick worked nicely for me. I used daemon.json to supply my TLS configuration as well as listen on 2376. Giving it nothing except a reference to daemon.json feels like a hack to avoid the hosts conflict.. but it works. Thanks again @webzakimbo

root@mnretrogamer029:~# cat /etc/docker/daemon.json
{
"data-root": "/mnt/dietpi_userdata/docker-data",
"log-driver": "journald",
"log-level": "warn",
"debug": false,
"hosts": ["unix:///var/run/docker.sock", "tcp://0.0.0.0:2376"],
"tlscacert": "/etc/docker/certs.d/ca.pem",
"tlscert": "/etc/docker/certs.d/server-cert.pem",
"tlskey": "/etc/docker/certs.d/server-key.pem",
"tlsverify": true
}

@parasiteoflife
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parasiteoflife commented Dec 29, 2023

what if I don't have systemd? ie. Unraid/Slackware

@valboosky
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valboosky commented Jan 26, 2024 •
edited
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on Ubuntu 22.04.3 couldn't get it to work with these instructions... do this:

Update Docker Configuration:
Edit the Docker daemon configuration file. The configuration file is typically located at /etc/docker/daemon.json. If it doesn't exist, you can create it.

sudo nano /etc/docker/daemon.json

Add the following content to the file:

{
"hosts": ["unix:///var/run/docker.sock", "tcp://0.0.0.0:2375"]
}

This configuration tells Docker to listen on both the UNIX socket and a TCP socket on all available network interfaces (0.0.0.0) on port 2375.

Restart Docker:
After making changes to the Docker daemon configuration, you need to restart the Docker daemon for the changes to take effect.

sudo systemctl restart docker

Adjust Firewall Rules (if necessary):
If you have a firewall enabled on your Ubuntu server, make sure to allow traffic on the Docker daemon port (default is 2375). You can use ufw (Uncomplicated Firewall) to do this:

bash

sudo ufw allow 2375

@dmote75
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dmote75 commented Feb 28, 2024 •
edited
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For Synology NAS (I am using DS923+) I found an easier way.
In your compose file for Homepage make sure to have the following listed under 'volumes'
- /var/run/docker.sock:/var/run/docker.sock

Then in your Homepage docker.yaml file, uncomment only this part:

# my-docker:
#   socket: /var/run/docker.sock

Once I did this it's working. Didn't have to mess with anything else.

@fbaligand
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fbaligand commented Feb 28, 2024

Thanks for your gist! It works great for me, with special case where I use Windows 10 & WSL2!

@HarshDev2
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HarshDev2 commented Mar 3, 2024

thanks, it worked for me

@youfly
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youfly commented Jul 6, 2024 •
edited
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For everyone finding this page and looking for instructions for Synology's new Container Manager,

  1. sudo vi /var/packages/ContainerManager/etc/dockerd.json

change to: {"data-root":"/var/packages/ContainerManager/var/docker","log-driver":"db","registry-mirrors":[],"storage-driver":"aufs","hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]}
(basically add the stuff from the original step 1 to the end, without the curly-brackets {} )

  1. systemctl daemon-reload
  2. sudo systemctl restart pkg-ContainerManager-dockerd

You may need to repeat these steps when the Container Manager package gets updated. So far it's working for me

Hi,bro. I'm trying to add the proxy option for the dockerd.json,there is some problem for me. I had read the docs of how to set the value of daemon-proxy,but the error still exsit.

  "proxies": {
    "http-proxy": "http://proxy.example.com:80",
    "https-proxy": "https://proxy.example.com:443",
    "no-proxy": "*.test.example.com,.example.org",
  }

unable to configure the Docker daemon with file /var/packages/ContainerManager/etc/dockerd.json: the following directives don't match any configuration option: http-proxy, https-proxy, no-proxy

{"data-root":"/var/packages/ContainerManager/var/docker","log-driver":"db","proxies":{"http-proxy":"http://127.0.0.1:7890","https-proxy":"http://127.0.0.1:7890","no-proxy":"localhost,127.0.0.1"},"registry-mirrors":[],"storage-driver":"aufs"} can you give me some help? appreciate it.

requre docked 23.0 or later,the synology is 20.10.3

@yangxh1992
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yangxh1992 commented Aug 20, 2024

Here's another way that worked for me:

/etc/systemd/system/docker.service.d/override.conf

[Service]
 ExecStart=
 ExecStart=/usr/bin/dockerd --config-file /etc/docker/daemon.json

/etc/docker/daemon.json

{
  "hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]
}

is worked thank you so much

@4thel00z
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4thel00z commented Oct 9, 2024 •
edited
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Exposing the docker daemon on 0.0.0.0 especially on something which faces the internet is a TERRIBLE idea!

It's literally like giving everyone sudo access...

Bind to 127.0.0.1 and portforward.

You don't even have to, the docker client can speak ssh) via: DOCKER_HOST=“ssh://user@remotehost

@gsemet
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gsemet commented Nov 3, 2024

i had to do the following:

$ cat /etc/systemd/system/docker.service.d/override.conf
[Service]
 ExecStart=
 ExecStart=/usr/sbin/dockerd --config-file /etc/docker/daemon.overrided.json

$ cat /etc/docker/daemon.overrided.json
{
  "hosts": ["tcp://0.0.0.0:2375", "unix:///var/run/docker.sock"]
}

The binary is in /usr/sbin/dockerd, and changing the daemon.json conflicted with the default parameter -H fd://

@kostakoff
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kostakoff commented May 3, 2025 •
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for ubuntu /etc/systemd/system/docker.service.d/override.conf

[Service]
ExecStart= 
ExecStart=/usr/bin/dockerd --containerd=/run/containerd/containerd.sock

@shyd
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shyd commented Jun 5, 2025 •
edited
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Thanks!

For Raspberry Pi bookworm it is

[Service]
ExecStart=
ExecStart=/usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock -H tcp://0.0.0.0:2375

without the daemon.json

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