Add contrib/nuke-graph-directory.sh script to clean out old /var/lib/docker directories much more easily

Signed-off-by: Andrew Page <admwiggin@gmail.com>

contrib/nuke-graph-directory.sh

@@ -0,0 +1,64 @@
+#!/bin/sh
+set -e
+
+dir="$1"
+
+if [ -z "$dir" ]; then
+	{
+		echo 'This script is for destroying old /var/lib/docker directories more safely than'
+		echo '  "rm -rf", which can cause data loss or other serious issues.'
+		echo
+		echo "usage: $0 directory"
+		echo "   ie: $0 /var/lib/docker"
+	} >&2
+	exit 1
+fi
+
+if [ "$(id -u)" != 0 ]; then
+	echo >&2 "error: $0 must be run as root"
+	exit 1
+fi
+
+if [ ! -d "$dir" ]; then
+	echo >&2 "error: $dir is not a directory"
+	exit 1
+fi
+
+dir="$(readlink -f "$dir")"
+
+echo
+echo "Nuking $dir ..."
+echo '  (if this is wrong, press Ctrl+C NOW!)'
+echo
+
+( set -x; sleep 10 )
+echo
+
+dir_in_dir() {
+	inner="$1"
+	outer="$2"
+	[ "${inner#$outer}" != "$inner" ]
+}
+
+# let's start by unmounting any submounts in $dir
+#   (like -v /home:... for example - DON'T DELETE MY HOME DIRECTORY BRU!)
+for mount in $(awk '{ print $5 }' /proc/self/mountinfo); do
+	mount="$(readlink -f "$mount" || true)"
+	if dir_in_dir "$mount" "$dir"; then
+		( set -x; umount -f "$mount" )
+	fi
+done
+
+# now, let's go destroy individual btrfs subvolumes, if any exist
+if command -v btrfs &> /dev/null; then
+	root="$(df "$dir" | awk 'NR>1 { print $NF }')"
+	for subvol in $(btrfs subvolume list -o "$root" 2>/dev/null | awk -F' path ' '{ print $2 }'); do
+		subvolDir="$root/$subvol"
+		if dir_in_dir "$subvolDir" "$dir"; then
+			( set -x; btrfs subvolume delete "$subvolDir" )
+		fi
+	done
+fi
+
+# finally, DESTROY ALL THINGS
+( set -x; rm -rf "$dir" )