# Exec node under docker
**URL:** https://discourse.nodered.org/t/exec-node-under-docker/84748
**Category:** General
**Tags:** docker
**Created:** [20 January 2024 05:45 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748 "2024-01-20T05:45:58Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@avronw](https://discourse.nodered.org/u/avronw)
#### Post date: [20 January 2024 05:45 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/1 "2024-01-20T05:45:58Z")
I want to run a standalone utility that would normally be found under /usr/bin, but given the node-red docker instance can't access that, I moved it into the /data directory that is mounted and functional. I'd assumed that when the exec node called it at /data/utility, it would be able to execute.
So, using 'bash /data/utility' gets me a 'cannot execute binary file' response and error 126.
I'm not great with linux, so assume this is a permissions thing on that utility file, but what should I be doing to make it executable to the exec node?
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### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [20 January 2024 06:08 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/2 "2024-01-20T06:08:33Z")
> [@avronw](#):
>
> I'm not great with linux, so assume this is a permissions thing on that utility file
I don't think so.
You are trying to interpret the file as a shell script ("bash /data/utility") and I suspect that it's an executable not a script file, possibly even something compiled for a different CPU architecture.
\*\*\* What does `file /data/utility` show?
\*\*\* What about `file /usr/bin/true` ?
> [@avronw](#):
>
> I want to run a standalone utility that would normally be found under /usr/bin
It is not usual or sensible to put your own files in /usr/bin; to put programs in /data is no better. ~/bin might be more appropriate (and log back in to add it to $PATH).
I know nothing about Docker but it seems improbable that it cannot access operating system utilities in /usr/bin. If not, how can it do anything at all?
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### Author:  [@avronw](https://discourse.nodered.org/u/avronw)
#### Post date: [20 January 2024 06:54 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/3 "2024-01-20T06:54:39Z")
I understand that a container only has access to a sandboxed partial environment that is a minimum necessary to run the specific application, so has no access to the underlying os.
I think you're right that perhaps the way I'm calling it is a problem, or it is permissions.
From within the container, performing a **file /data/stress** provides the following:
_~$ file /data/stress_
_/data/stress: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=800abdc1177388d244b2d95344b87604e53c0c89, stripped_
**file /usr/bin/true** provides:
_~$ file /usr/bin/true_
_/usr/bin/true: cannot open `/usr/bin/true' (No such file or directory)_
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### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [20 January 2024 07:17 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/4 "2024-01-20T07:17:06Z")
> [@avronw](#):
>
> /usr/bin/true: cannot open `/usr/bin/true' (No such file or directory)
Ah well, on my OS true is in /usr/bin but no matter.
> [@avronw](#):
>
> _~$ file /data/stress_
> _/data/stress: ELF 64-bit LSB pie executable_
It is indeed an executable.
1. Ensure that the file permissions indicate it as executable. `chmod +x /data/stress`
2. Change the exec node command to `/data/stress`.
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### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [20 January 2024 09:00 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/5 "2024-01-20T09:00:38Z")
The default docker image is built on Alpine and not Debian (it's smaller and faster to start). So the host binary is incompatible (most probably the bindings) - so you could try the debian based docker image instead (if that is what your host is using)
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### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [20 January 2024 09:25 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/6 "2024-01-20T09:25:20Z")
Ah yes, that's exactly why I wanted to compare two file commands 😉.
Nicely explained.
I still think the "Cannot execute binary file" comes from trying to interpret the executable as a script file though?
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### Author:  [@jodelkoenig](https://discourse.nodered.org/u/jodelkoenig)
#### Post date: [20 January 2024 09:42 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/7 "2024-01-20T09:42:12Z")
You can still "escape" your docker container with the exec node by ssh'ing onto the host system and attach your command at the end.
I do so with a certificate and a special user with non-root rights in order to do some backup jobs on host level.
I decribed in more details how I am doing it [here](https://discourse.nodered.org/t/node-red-in-a-docker-container-doesnt-seem-to-be-able-to-execute-some-programs-with-the-exec-node/78826/3)
EDIT
Aaaand 🙂 ... if you'd like to run a script which temporarily stops your docker container after you started the script with above mentioned approach, check [here](https://discourse.nodered.org/t/does-anybody-know-the-correct-command-line-for-sshpass-to-ssh-in-start-a-script-and-log-out-again/82974/7) to get everything up and running again, as you like.
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### Author:  [@avronw](https://discourse.nodered.org/u/avronw)
#### Post date: [21 January 2024 03:00 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/8 "2024-01-21T03:00:49Z")
Thanks, this is a good idea, but probably too much of a workaround for now and may be the plan B, but did get me thinking about using files as a semiphore to pass messages or requests to host.
So, I solved the problem by doing this:
- I wrote a bash script (watcher.sh) that watches a folder within the node-red docker volume (i.e. the host of node-red's /data/requests).
- Node-red writes files (requests) to that folder (/data/requests), either using the filename as the request indicator (placing a json request inside the file).
- The watcher.sh is notified of the new file, reads the filename as the request (or the json within the file), and performs the request.
- On completion, the watcher writes a confirmation file back to the node-red docker volume (/data/responses), either with a meaningful filename or containing a response json within the file.
I set the watcher.sh script up to run as a service, and ensured _systemd_ had execute rights, and that the service auto-starts on boot. It works like a charm!
It is a great way to allow a container to request a host action (such as starting or stopping another docker container), or passing basic messages between co-located docker containers.
Thanks for the idea, it is very much appreciated.
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### Author:  [@avronw](https://discourse.nodered.org/u/avronw)
#### Post date: [21 January 2024 03:02 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/9 "2024-01-21T03:02:03Z")
Thanks, this is a great explanation.
So, theoretically, if I have a local copy of a standalone utility that is built on Alpine, it should execute within the container context?
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### Author:  [@dceejay](https://discourse.nodered.org/u/dceejay)
#### Post date: [21 January 2024 05:20 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/10 "2024-01-21T05:20:04Z")
Yes that could work
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### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [4 February 2024 05:21 UTC](https://discourse.nodered.org/t/exec-node-under-docker/84748/11 "2024-02-04T05:21:03Z")
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