Docker API - Exec start returns "Page not found" - api

Question

I'm trying to execute a command in a running docker container through the Docker Engine API with cURL. I'm following the instructions in the API doc.First I create an exec instance and as a response I receive the ID of the created exec.
Then I use the this ID when I try to send a request to start this exec, which looks as follows:
$ curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" -x POST "http:/v1.29/exec/myExecID/start"
But the response from that request is:
{"message":"page not found"}
This is my Docker version:
Client:
Version: 17.05.0-ce
API version: 1.29
Go version: go1.7.5
Git commit: 89658be
Built: Thu May 4 22:10:54 2017
OS/Arch: linux/amd64
Server:
Version: 17.05.0-ce
API version: 1.29 (minimum version 1.12)
Go version: go1.7.5
Git commit: 89658be
Built: Thu May 4 22:10:54 2017
OS/Arch: linux/amd64
Experimental: false
In the code in the Moby's repository, they call the absolutely same address.
Anyone else faced this problem ever before? I'll be glad if you share your experience.

Answer 1

Maybe it happens because you did not include the request body like this :
-d '{"Detach": false, "Tty": false}'
If you even get an error like below :
{"message":"No such exec instance '<ID>' found in daemon"}
That means you have not created an instance for exec. If so, you need to create a new instance
curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
-d '{"AttachStdin": false, "AttachStdout": true, "AttachStderr": true, "DetachKeys": "ctrl-p,ctrl-q", "Tty": false, "Cmd": ["date"], "Env": ["FOO=bar", "BAZ=quux"]}' \
-X POST http:/v1.29/containers/fafe141c1a2b/exec
Output (example) :
{"Id":"70f08c296d460d2fe254ecd0f8e0416777a6b938bb74a325ffc76405d33d3526"}
After that then you can do exec as shown below :
curl --unix-socket /var/run/docker.sock -H "Content-Type: application/json" \
-d '{"Detach": false, "Tty": false}' \
-X POST http:/v1.29/exec/70f08c296d460d2fe254ecd0f8e0416777a6b938bb74a325ffc76405d33d3526/start
I've tried that way and it works, hopefully can help!