config: platform dependent user attributes

This introduces verbiage of fields that may occur in json (technically
optional), but is required on certain platforms (e.g. Linux).

Not adding a "name" string, as that is not a requirement yet.

In the event a windows runtime shows up, I could imagine an `sid`, but
we'll get to that when it happens.

Closes opencontainers#135
Related to opencontainers#166

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

config.go

@@ -33,6 +33,17 @@ type Process struct {
 	Cwd string `json:"cwd"`
 }
 
+// User specifies linux specific user and group information for the container's
+// main process.
+type User struct {
+	// UID is the user ID the Process is executed as. (this field is platform dependent)
+	UID uint32 `json:"uid,omitempty"`
+	// GID is the group ID the Process is executed as. (this field is platform dependent)
+	GID uint32 `json:"gid,omitempty"`
+	// AdditionalGids are additional group ids set for the container's process. (this field is platform dependent)
+	AdditionalGids []uint32 `json:"additionalGids,omitempty"`
+}
+
 // Root contains information about the container's root filesystem on the host.
 type Root struct {
 	// Path is the absolute path to the container's root filesystem.

config.md

@@ -76,9 +76,9 @@ The runtime MUST mount entries in the listed order.
 The user for the process is a platform-specific structure that allows specific control over which user the process runs as.
 For Linux-based systems the user structure has the following fields:
 
-* **`uid`** (int, required) specifies the user id.
-* **`gid`** (int, required) specifies the group id.
-* **`additionalGids`** (array of ints, optional) specifies additional group ids to be added to the process.
+* **`uid`** (int, required on Linux) specifies the user id.
+* **`gid`** (int, required on Linux) specifies the group id.
+* **`additionalGids`** (array of ints, optional on Linux) specifies additional group ids to be added to the process.
 
 *Example (Linux)*
 

config_linux.go

@@ -12,14 +12,3 @@ type Linux struct {
 	// Capabilities are linux capabilities that are kept for the container.
 	Capabilities []string `json:"capabilities"`
 }
-
-// User specifies linux specific user and group information for the container's
-// main process.
-type User struct {
-	// UID is the user id.
-	UID uint32 `json:"uid"`
-	// GID is the group id.
-	GID uint32 `json:"gid"`
-	// AdditionalGids are additional group ids set for the container's process.
-	AdditionalGids []uint32 `json:"additionalGids,omitempty"`
-}