add ability to export initfs as block (#268)

This refactors the rootfs command to produce an image and have the
ability to create an ext4 formatted block of the init filesystem
directly from the command.

closes #220

Signed-off-by: crosbymichael <michael_crosby@apple.com>

Makefile

@@ -57,7 +57,12 @@ containerization:
 init: containerization vminitd
 	@echo Creating init.ext4...
 	@rm -f bin/init.rootfs.tar.gz bin/init.block
-	@./bin/cctl rootfs create --vminitd vminitd/bin/vminitd --labels org.opencontainers.image.source=https://github.com/apple/containerization --vmexec vminitd/bin/vmexec bin/init.rootfs.tar.gz vminit:latest
+	@./bin/cctl rootfs create \
+		--vminitd vminitd/bin/vminitd \
+		--labels org.opencontainers.image.source=https://github.com/apple/containerization \
+		--vmexec vminitd/bin/vmexec \
+		--image vminit:latest \
+		bin/init.rootfs.tar.gz
 
 .PHONY: cross-prep
 cross-prep:

Sources/Containerization/Image/Unpacker/EXT4Unpacker.swift

@@ -32,13 +32,56 @@ public struct EXT4Unpacker: Unpacker {
         self.blockSizeInBytes = blockSizeInBytes
     }
 
-    public func unpack(_ image: Image, for platform: Platform, at path: URL, progress: ProgressHandler? = nil) async throws -> Mount {
+    #if os(macOS)
+    /// Performs the unpacking of a tar archive into a filesystem.
+    /// - Parameters:
+    ///   - archive: The archive to unpack.
+    ///   - compression: The compression to use when unpacking the image.
+    ///   - path: The path to the filesystem that will be created.
+    public func unpack(
+        archive: URL,
+        compression: ContainerizationArchive.Filter,
+        at path: URL
+    ) throws {
+        let cleanedPath = try prepareUnpackPath(path: path)
+        let filesystem = try EXT4.Formatter(
+            FilePath(cleanedPath),
+            minDiskSize: blockSizeInBytes
+        )
+        defer { try? filesystem.close() }
+
+        try filesystem.unpack(
+            source: archive,
+            format: .paxRestricted,
+            compression: compression,
+            progress: nil
+        )
+    }
+    #endif
+
+    /// Returns a `Mount` point after unpacking the image into a filesystem.
+    /// - Parameters:
+    ///   - image: The image to unpack.
+    ///   - platform: The platform content to unpack.
+    ///   - path: The path to the directory where the filesystem will be created.
+    ///   - progress: The progress handler to invoke as the unpacking progresses.
+    public func unpack(
+        _ image: Image,
+        for platform: Platform,
+        at path: URL,
+        progress: ProgressHandler? = nil
+    ) async throws -> Mount {
         #if !os(macOS)
         throw ContainerizationError(.unsupported, message: "Cannot unpack an image on current platform")
         #else
-        let blockPath = try prepareUnpackPath(path: path)
+        let cleanedPath = try prepareUnpackPath(path: path)
         let manifest = try await image.manifest(for: platform)
-        let filesystem = try EXT4.Formatter(FilePath(path), minDiskSize: blockSizeInBytes)
+        let filesystem = try EXT4.Formatter(
+            FilePath(
+                cleanedPath
+            ),
+            minDiskSize: blockSizeInBytes
+        )
         defer { try? filesystem.close() }
 
         for layer in manifest.layers {
@@ -64,7 +107,7 @@ public struct EXT4Unpacker: Unpacker {
 
         return .block(
             format: "ext4",
-            source: blockPath,
+            source: cleanedPath,
             destination: "/",
             options: []
         )

Sources/cctl/RootfsCommand.swift

@@ -46,9 +46,14 @@ extension Application {
             @Option(name: .long, help: "Labels to add to the built image of the form <key1>=<value1>, [<key2>=<value2>,...]")
             var labels: [String] = []
 
-            @Argument var rootfsPath: String
+            @Option(name: .customLong("image"), help: "The name of the image to produce.")
+            var imageName: String?
 
-            @Argument var tag: String
+            @Option(name: .customLong("ext4"), help: "The path to an ext4 image to create.")
+            var ext4File: String?
+
+            // The path where the intermediate tar archive is created.
+            @Argument var tarPath: String
 
             private static let directories = [
                 "bin",
@@ -63,19 +68,51 @@ extension Application {
             ]
 
             func run() async throws {
-                try await writeArchive()
-                let p = try Platform(from: platformString)
-                let rootfs = URL(filePath: rootfsPath)
-                let labels = Application.parseKeyValuePairs(from: labels)
-                _ = try await InitImage.create(
-                    reference: tag, rootfs: rootfs,
-                    platform: p, labels: labels,
-                    imageStore: Application.imageStore,
-                    contentStore: Application.contentStore)
+                let path = URL(filePath: self.tarPath)
+                try await writeArchive(path: path)
+
+                if let image = self.imageName {
+                    print("creating initfs image \(image)...")
+                    try await outputImage(
+                        path: path,
+                        reference: image
+                    )
+                }
+
+                if let ext4Path = self.ext4File {
+                    print("creating initfs ext4 image at \(ext4Path)...")
+                    try await outputExt4(
+                        archive: path,
+                        to: URL(filePath: ext4Path)
+                    )
+                }
             }
 
-            private func writeArchive() async throws {
-                let writer = try ArchiveWriter(format: .pax, filter: .gzip, file: URL(filePath: rootfsPath))
+            private func outputExt4(archive: URL, to path: URL) async throws {
+                let unpacker = EXT4Unpacker(blockSizeInBytes: 256.mib())
+
+                try unpacker.unpack(archive: archive, compression: .gzip, at: path)
+            }
+
+            private func outputImage(path: URL, reference: String) async throws {
+                let p = try Platform(from: platformString)
+                let labels = Application.parseKeyValuePairs(from: labels)
+                _ = try await InitImage.create(
+                    reference: reference,
+                    rootfs: path,
+                    platform: p,
+                    labels: labels,
+                    imageStore: Application.imageStore,
+                    contentStore: Application.contentStore
+                )
+            }
+
+            private func writeArchive(path: URL) async throws {
+                let writer = try ArchiveWriter(
+                    format: .pax,
+                    filter: .gzip,
+                    file: path,
+                )
                 let ts = Date()
                 let entry = WriteEntry()
                 entry.permissions = 0o755
@@ -84,6 +121,7 @@ extension Application {
                 entry.group = 0
                 entry.owner = 0
                 entry.fileType = .directory
+
                 // create the initial directory structure.
                 for dir in Self.directories {
                     entry.path = dir