OCI configurations for linglong containers

Directory [config.d] contains OCI configuration patches and generators. They will be applied in file name order.

generator

Files in [config.d] that is executable for linglong runtime program are treated as OCI configuration generators for linglong.

They will be executed by linglong runtime program with the constructing OCI configuration writed into their stdin. They should print FULL content of that modified OCI configuration to their stdout, and print error message or warning to their stderr.

If anything goes wrong, for example:

• the OCI configuration read from stdout failed to be parsed;
• generator exit with non-zero return code;
• generator crashed;
• ...

That generator will be ignored.

OCI configuration patches

Files in [config.d] that is NOT executable for linglong runtime program and ends with .json are treated as OCI configuration patches.

They will be read by linglong runtime program, then the items in patch field will be parsed as JSON Patch then be applied one by one.

If anything goes wrong, for example:

• the json file failed to be parsed as OCI configuration patch;
• the ociVersion field is not equals to constructing configuration;
• ...

That patch will be ignored.

The json schema definition of OCI configuration patch file can be found at /api/schema/v1.yaml.

Application-specific patches

Patches in application ID-named directories are application-specific and apply after global patches

Examples

• Global patch: 99-dump-conf
• App patch: com.example.app/99-test.json

com.example.app/99-test.json:

{
  "ociVersion": "1.0.1",
  "patch": [
    {
      "op": "add",
      "path": "/mounts/-",
      "value": {
        "destination": "/opt/host-apps/",
        "type": "bind",
        "source": "/opt/apps",
        "options": ["rbind"]
      }
    }
  ]
}

com.example.app/99-test.json add an extra mounts, which bind host's /opt/apps to container's /opt/host-apps, this patch will applied after 99-dump-conf.

99-dump-conf can write following content to print the container's configuration:

#!/bin/sh

content=$(cat -)
echo $content >&2
echo ${content}