Dir owner 'nobody' and group 'root' after mounting container volume with `addGroupOwner` set to true.

Question

When running a lambda function component in Greengrass v2.12.2 the mounted volume does not seem to have the correct owner.

For the host dir I have the following owner, group and permissions: `drwxr-xr-x root root`.

Greengrass is installed with `--component-default-user ggc_user:ggc_group` which I can confirm in the effective config as `posixUser: "ggc_user:ggc_group"`

My lambda configuration is as follows
```
{
  "lambdaFunction": {
    ...
    "componentLambdaParameters": {
      "pinned": true,
      ...
      "linuxProcessParams": {
        ...
        "containerParams": {
          "volumes": [
            {
              "sourcePath": "/host/dir",
              "destinationPath": "/dir",
              "addGroupOwner": true,
              "permission": "rw"
            }
          ]
        }
      }
    }
  }
}
```
And in my lambda the owner I get is `nobody` and group is `root` while the posix permisssions for the mounted directory are `drwxr-xr-x`.

Also neithrer `addGroupOwner` nor `permission` seem to make a difference in my case; it's always `drwxr-xr-x nobody root`.

(Just in case it is relevant I fetch the owner programmatically in Kotlin/Java with `Files.getOwner(path)` and group with `Files.getAttribute(this, "posix:group", NOFOLLOW_LINKS)`)

I was expecting the group to be `ggc_group` and owner to be `ggc_user`. Am I missing something?

My ultimate goal is to be able to create a file in the mounted volume but I get permission denied not surprisingly.

Accepted Answer

Hello,

When using local resources the local resources must not be owned by root, or else only root can access those resources. Please use a directory that you have permission to write to. Lambdas are always started with a current working directory which is writable, you can write to `.`; the current working directory without any other changes.

You are migrating from Greengrass V1, what was the exact configuration of your lambda in Greengrass V1? That same configuration should be used with Greengrass v2.

AddGroupOwner would mean that your lambda is execute with the group ID which owns the volume. Your lambda cannot run as the root group, so this has no effect as root owns the volume. Using the default path that Greengrass gives you will work without needing to mount anything. File permissions are not changed by this setting.

If you still need assistance please enable DEBUG level logs in the Greengrass Nucleus component configuration and provide the debug logs from the lambda component. They will show what is happening.

Regards,

Michael

Dir owner 'nobody' and group 'root' after mounting container volume with `addGroupOwner` set to true.

Relevanter Inhalt