EC2: Add experimental cloud-init images

Known issues:

1. The ec2-user user is created with a homedir of /usr/home/ec2-user
instead of /home/ec2-user; this appears to be a bug in cloud-init's
FreeBSD support.

2. Cloud-init configures IPv4 networking but not IPv6 networking.

releng/14.0 candidate.

Discussed with:	gjb
Reviewed by:	imp
MFC after:	5 days
Relnotes:	yes
Sponsored by:	https://www.patreon.com/cperciva
Differential Revision:	https://reviews.freebsd.org/D41793

release/Makefile.vm

@@ -30,8 +30,9 @@ BASIC-CI_FSLIST=	ufs
 BASIC-CI_DESC=		Image for CI
 EC2_FORMAT=	raw
 EC2_FSLIST=	ufs zfs
-EC2_DESC=	Amazon EC2 image
-EC2_FLAVOURS=	BASE
+EC2_FLAVOURS=	BASE CLOUD-INIT
+EC2-BASE_DESC=	Amazon EC2 image
+EC2-CLOUD-INIT_DESC=	Amazon EC2 Cloud-Init image
 GCE_FORMAT=	raw
 GCE_FSLIST=	ufs zfs
 GCE_DESC=	Google Compute Engine image

release/tools/ec2-cloud-init.conf

@@ -0,0 +1,31 @@
+#!/bin/sh
+
+. ${WORLDDIR}/release/tools/ec2.conf
+
+# Packages to install into the image we're creating.  In addition to packages
+# present on all EC2 AMIs, we install cloud-init.
+export VM_EXTRA_PACKAGES="${VM_EXTRA_PACKAGES} net/cloud-init"
+
+# Services to enable in rc.conf(5).
+export VM_RC_LIST="${VM_RC_LIST} cloudinit sshd"
+
+vm_extra_pre_umount() {
+	# Configuration common to all EC2 AMIs
+	ec2_common
+
+	# Configure cloud-init
+	cat <<-'EOF' > ${DESTDIR}/usr/local/etc/cloud/cloud.cfg.d/98_ec2.cfg
+		disable_root: true
+		system_info:
+		  distro: freebsd
+		  default_user:
+		    name: ec2-user
+		    lock_passwd: True
+		    groups: [wheel]
+		    shell: /bin/sh
+		    # Currently broken, cloud-init hard-codes to /usr/home/*
+		    homedir: /home/ec2-user
+	EOF
+
+	return 0
+}