Docker API - Exec start returns "Page not found"

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.

You have http:// localhost in the URL. It looks like you are calling some web server on your host instead of the Docker engine API. — vempo, May 31 '17 at 15:04
Yeah, sorry, I just fixed my question. The problem is that both ways it doesn't work :) — Radoslav Stoyanov, May 31 '17 at 15:05

score 1 · Accepted Answer · answered May 31 '17 at 15:55

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!

Yeah, it was because I didn't include the request body, which I thought that is not required. — Radoslav Stoyanov, Jun 01 '17 at 08:22

Docker API - Exec start returns "Page not found"

1 Answers1