[Buildroot] [PATCH 1/1] fs/aci: Add App Container Image (ACI) support to filesystems

[Brian 'redbeard' Harrington <redbeard@coreos.com>]

App Container Images (ACI) are a Linux containerization image format
defined as a part of the AppC specification as defined by CoreOS,
Red Hat, Google, and community members. These images consist of a Linux
userland and a JSON metadata file describing how to execute the actual
runtime.

This filesystem package utilizes Buildroot for the generation of
the userland and provides the user with a mechanism for configuring the
contents of the manifest file.

Signed-off-by: Brian 'redbeard' Harrington <redbeard@coreos.com>
---
 fs/Config.in     |  1 +
 fs/aci/Config.in | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/aci/aci.json  | 34 ++++++++++++++++++++++++++
 fs/aci/aci.mk    | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 177 insertions(+)
 create mode 100644 fs/aci/Config.in
 create mode 100644 fs/aci/aci.json
 create mode 100644 fs/aci/aci.mk

diff --git a/fs/Config.in b/fs/Config.in
index 51ccf28..1c468c5 100644
--- a/fs/Config.in
+++ b/fs/Config.in
@@ -1,5 +1,6 @@
 menu "Filesystem images"
 
+source "fs/aci/Config.in"
 source "fs/axfs/Config.in"
 source "fs/cloop/Config.in"
 source "fs/cpio/Config.in"
diff --git a/fs/aci/Config.in b/fs/aci/Config.in
new file mode 100644
index 0000000..7dcac6b
--- /dev/null
+++ b/fs/aci/Config.in
@@ -0,0 +1,72 @@
+config BR2_TARGET_ROOTFS_ACI
+	bool "Generate App Container Image (ACI)"
+	default y
+	select BR2_PACKAGE_HOST_JQ
+	help
+	  Build an App Container Image for use with a Linux
+	  containerization engine like rkt, Kurma, 3ofCoins, nosecone,
+	  etc.
+
+choice
+	prompt "Compression method"
+	default BR2_TARGET_ROOTFS_ACI_NONE
+	depends on BR2_TARGET_ROOTFS_ACI
+	help
+	  Select compressor for application container image
+
+config BR2_TARGET_ROOTFS_ACI_NONE
+	bool "no compression"
+	help
+	  Do not compress the ACI.
+
+config BR2_TARGET_ROOTFS_ACI_GZIP
+	bool "gzip"
+	help
+	  Do compress the ACI with gzip.
+
+config BR2_TARGET_ROOTFS_ACI_BZIP2
+	bool "bzip2"
+	help
+	  Do compress the ACI with bzip2.
+
+config BR2_TARGET_ROOTFS_ACI_LZMA
+	bool "lzma"
+	help
+	  Do compress the ACI with lzma.
+
+config BR2_TARGET_ROOTFS_ACI_LZO
+	bool "lzo"
+	help
+	  Do compress the ACI with lzop.
+
+config BR2_TARGET_ROOTFS_ACI_XZ
+	bool "xz"
+	help
+	  Do compress the ACI with xz.
+
+endchoice
+
+config BR2_TARGET_ROOTFS_ACI_OPTIONS_NAME
+	string "Name of the ACI image (e.g. example.com/my_app)"
+	depends on BR2_TARGET_ROOTFS_ACI 
+	help
+	  A human-readable name for this App Container Image
+
+comment "ACI images must have a name"
+	depends on BR2_TARGET_ROOTFS_ACI_OPTIONS_NAME = ""
+
+config BR2_TARGET_ROOTFS_ACI_OPTIONS_EXEC
+	string "Command to execute inside the container (e.g. /bin/sh)"
+	depends on BR2_TARGET_ROOTFS_ACI 
+	help
+	  Executable to launch and any flags
+
+config BR2_TARGET_ROOTFS_ACI_OPTIONS_VERSION
+	string "Version number of the container (e.g. v1.3.2)"
+	depends on BR2_TARGET_ROOTFS_ACI
+	help
+	  When combined with "name", this SHOULD be unique for every 
+	  build of an app (on a given "os"/"arch" combination).
+
+comment "ACI images should be supplied with a version"
+	depends on BR2_TARGET_ROOTFS_ACI_OPTIONS_VERSION = ""
diff --git a/fs/aci/aci.json b/fs/aci/aci.json
new file mode 100644
index 0000000..bce9d39
--- /dev/null
+++ b/fs/aci/aci.json
@@ -0,0 +1,34 @@
+{
+	"acKind":"ImageManifest",
+	"acVersion":"0.7.4",
+	"name":env.aciname,
+	"labels":
+		[{
+			"name":"os",
+			"value":"linux"
+		},{
+			"name":"arch",
+			"value": env.aciarch
+		},{ 
+			"name":"version",
+			"value": env.aciver
+		}],
+	"app":
+	{
+		"exec":
+			[
+			env.aciexec
+			],
+		"user": (if (env.aciexec == "") then "0" else env.aciexec end),
+		"group": (if (env.aciexec == "") then "0" else env.aciexec end)
+	},
+	"annotations":
+	[{
+		"name": "buildroot.org/aci",
+		"value": "Generated by Buildroot"
+	},
+	{
+		"name": "created",
+		"value": env.created_at 
+	}]
+}
diff --git a/fs/aci/aci.mk b/fs/aci/aci.mk
new file mode 100644
index 0000000..5af6c13
--- /dev/null
+++ b/fs/aci/aci.mk
@@ -0,0 +1,70 @@
+################################################################################
+#
+# Generate ACI image
+# https://github.com/appc/spec/blob/master/spec/aci.md
+#
+################################################################################
+ROOTFS_ACI_DEPENDS += host-jq
+
+# ACIs follow the Golang naming spec for CPU  architecture
+
+ifeq ($(BR2_arm),y)
+ifeq ($(BR2_ARM_CPU_ARMV5),y)
+	ACI_ARCH = arm5l
+else ifeq ($(BR2_ARM_CPU_ARMV6),y)
+	ACI_ARCH = arm6l
+else ifeq ($(BR2_ARM_CPU_ARMV7A),y)
+	ACI_ARCH = arm7l
+endif
+else ifeq ($(BR2_armeb),y)
+ifeq ($(BR2_ARM_CPU_ARMV5),y)
+	ACI_ARCH = arm5b
+else ifeq ($(BR2_ARM_CPU_ARMV6),y)
+	ACI_ARCH = arm6b
+else ifeq ($(BR2_ARM_CPU_ARMV7A),y)
+	ACI_ARCH = arm7b
+endif
+else ifeq ($(BR2_aarch64),y)
+	ACI_ARCH = aarch64
+else ifeq ($(BR2_aarch64_be),y)
+	ACI_ARCH = aarch64_be
+else ifeq ($(BR2_i386),y)
+	ACI_ARCH = 386
+else ifeq ($(BR2_x86_64),y)
+	ACI_ARCH = amd64
+else ifeq ($(BR2_powerpc),y)
+	ACI_ARCH = ppc64
+endif
+
+# For the generation of our ACI we include a timestamp and pass the variables
+# from the main configuration into jq to generate a JSON manifest.  We then
+# create the TAR archive of all components, making sure all paths are
+# represented correctly.
+
+define ROOTFS_ACI_CMD
+	created_at='$(shell date --rfc-3339=ns | tr " " "T")' \
+	aciname=$(BR2_TARGET_ROOTFS_ACI_OPTIONS_NAME) \
+	aciexec=$(BR2_TARGET_ROOTFS_ACI_OPTIONS_EXEC) \
+	aciver=$(BR2_TARGET_ROOTFS_ACI_OPTIONS_VERSION) \
+	aciarch=$(ACI_ARCH) \
+	$(HOST_DIR)/usr/bin/jq -n -f fs/aci/aci.json > $(TARGET_DIR)/manifest && \
+	tar -c$(TAR_OPTS)f $@ --xattrs --numeric-owner -C $(TARGET_DIR) \
+	  --transform 's,^\./,rootfs/,' --exclude=*/manifest manifest .
+endef
+
+# ACI images are required to end in ".aci" regardless of compression
+
+ifneq ($(BR2_TARGET_ROOTFS_ACI_NONE),y)
+
+define ROOTFS_ACI_MOVE
+	echo "br2 var - $(BR2_TARGET_ROOTFS_ACI_NONE)" && \
+	mv -f $(BINARIES_DIR)/rootfs.aci$(ROOTFS_ACI_COMPRESS_EXT) \
+		$(BINARIES_DIR)/rootfs.aci && \
+	echo "Compressed ACI moved to $(BINARIES_DIR)/rootfs.aci"
+
+endef
+
+ROOTFS_ACI_POST_GEN_HOOKS += ROOTFS_ACI_MOVE
+endif
+
+$(eval $(call ROOTFS_TARGET,aci))
-- 
2.4.11