Expand root to all available volume space when it's a partition

LICENSE.txt

@@ -1,4 +1,4 @@
-Copyright (c) 2017 Michael Crute
+Copyright (c) 2017-2020 Michael Crute
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of
 this software and associated documentation files (the "Software"), to deal in

README.md

@@ -9,11 +9,14 @@ and cloud platform support for small size and limited external dependencies.
 ## Requirements
 
 The most important feature of this bootstrapper is the very limited set of
-dependencies. In-fact, this works with just busybox -- provided the wget applet
-is built-in -- and resize2fs. The only required dependencies are:
+dependencies. In-fact, this works with just BusyBox (provided ash and wget
+are built in) and a couple utilities for expanding the root filesystem.
+The full list of required dependencies are:
 
 - bash-like shell (e.g. bash, dash, ash)
 - wget
+- sfdisk
+- partx
 - resize2fs
 
 ## Supported Features and Environments
@@ -33,7 +36,7 @@ those things. Instead it supports:
 - installing the instance's SSH keys in the EC2 user's authorized_keys file
 - running any script-like user data (must start with #!)
 - disabling root and the EC2 user's password
-- resizing root partition to available disk space
+- expanding root partition to available disk space
 
 These steps only run once. After the initial bootstrap the bootstrapper script
 is a no-op. To force the script to run again at boot time remove the file

tiny-ec2-bootstrap

@@ -66,11 +66,22 @@ _run_userdata() {
 		ec=$(cat "$ec_file")
 
 		echo "User Data Script Exit Status: $ec"
-		return $ec
+		return "$ec"
 	fi
 }
 
 _resize_root_partition() {
+	local mountpoint="$(mountpoint -n / | cut -d' ' -f1)"
+
+	# mountpoint is the second partition...
+	if echo "$mountpoint" | cut -d' ' -f1 | grep -qE '/(nvme\d+n\d+p|xvd[a-z]+)2$'; then
+		local volume="$(echo "$mountpoint" | sed -Ee 's/(nvme\d+n\d+|xvd[a-z]+)p?2/\1/')"
+		einfo "Expanding root partition to volume size..."
+		echo ", +" | sfdisk -q --no-reread -N 2 "$volume"
+		einfo "Updating kernel with new partition table..."
+		partx -u "$volume"
+	fi
+	einfo "Resizing..."
 	resize2fs "$(mountpoint -n / | cut -d' ' -f1)"
 }
 
@@ -86,7 +97,7 @@ start() {
 
 	ebegin "Disabling root password"; _disable_password root; eend $?
 	ebegin "Disabling $EC2_USER password"; _disable_password "$EC2_USER"; eend $?
-	ebegin "Resizing root partition"; _resize_root_partition; eend $?
+	ebegin "Expanding root partition"; _resize_root_partition; eend $?
 	ebegin "Setting ec2 hostname"; _update_hostname; eend $?
 	ebegin "Setting ec2 user ssh keys"; _set_ssh_keys "$EC2_USER"; eend $?
 	ebegin "Running ec2 user data script"; _run_userdata; eend $?