Run a command in a container with no shell?

Drone Support
1

The description of how commands works says that it converts them into a script run in /bin/sh. What about if the container image does not have /bin/sh in it? FROM scratch images are becoming pretty popular.

Actually, plugins/base appears not have have /bin/sh either:

$docker run --rm plugins/base:multiarch sh
docker: Error response from daemon: OCI runtime create failed: container_linux.go:345: starting container process caused "exec: \"sh\": executable file not found in $PATH": unknown.
2

The shell is only required when you have a commands section. You will not that plugins never have a commands section, hence why a shell is not required. Instead they use entrypoint and command which you can set directly in the yaml in lieu of commands if you prefer.

steps:
- name: foo
  image: bar
  entrypoint: [ /path/to/command ]
  command: [ "--one", "--two" ]
3

Ah, you can use entrypoint like k8s? I didn’t know. I tried to find the docs for the full config, but couldn’t find them.

So if I do the syntax above, it will run it without a shell?

4

yes

It is documented in the services section since this is where it is mostly used. This is the first time someone has asked me about using entrypoint and command in a pipeline step :slight_smile:

So if I do the syntax above, it will run it without a shell?

yes, here is a working example:

kind: pipeline
name: default
steps:
- name: foo
  image: alpine:3.8
  entrypoint: [ /bin/echo ]
  command: [ hello, world ]
5

Thanks Brad. There is a bug in one of the plugins in how it calls a command (already opened an issue, and a PR), but the plugin doesn’t have sh, so I thought I would keep the same one, just execute around it. Didn’t work as it required /bin/sh. Now I know how to work around it.

In the end, just took a different image and ran some installs. Suboptimal, but works.