feat(snap): automatic wallet backup on snap removal

README.md

@@ -112,6 +112,28 @@ sudo sysctl --system
 
 # Operations
 
+## Backup and restore
+
+Before planned maintenance, flush caches and create a snap snapshot:
+
+```bash
+sudo diode-node.flush
+sudo snap stop diode-node
+sudo snap save diode-node
+```
+
+When you remove the snap (`sudo snap remove diode-node`), the remove hook automatically archives critical node files (identity and wallet database) to `/var/backups/diode-node/diode_node_backup_<timestamp>.tar.gz`. The `backup-dir` system-files plug must be connected for this path to work; otherwise rely on `snap saved` within 31 days.
+
+To restore from an automatic backup after reinstalling:
+
+```bash
+sudo snap install diode-node
+sudo snap connect diode-node:backup-dir
+sudo snap stop diode-node.service
+sudo snap run --shell diode-node -c 'bin/restore_snap_backup /var/backups/diode-node/diode_node_backup_YYYY-MM-DD_HHMMSS.tar.gz'
+sudo snap start diode-node.service
+```
+
 ## See last service restart reason
 
 When running the snap installation then it's a two step process to see the last service restart reason:

scripts/restore_snap_backup.sh

@@ -0,0 +1,55 @@
+#!/bin/bash
+# Restore a diode-node backup created by the snap remove hook.
+set -euo pipefail
+
+usage() {
+	cat <<EOF
+Usage: $0 <backup.tar.gz>
+
+Restores node identity and wallet data from an automatic snap-removal backup.
+Run after reinstalling diode-node and stopping the service:
+
+  sudo snap install diode-node
+  sudo snap connect diode-node:backup-dir
+  sudo snap stop diode-node.service
+  sudo snap run --shell diode-node -c 'bin/restore_snap_backup /var/backups/diode-node/diode_node_backup_YYYY-MM-DD_HHMMSS.tar.gz'
+  sudo snap start diode-node.service
+EOF
+}
+
+if [[ $# -ne 1 ]]; then
+	usage
+	exit 1
+fi
+
+backup_file="$1"
+
+if [[ ! -f "$backup_file" ]]; then
+	echo "Backup file not found: $backup_file" >&2
+	exit 1
+fi
+
+if [[ -z "${SNAP:-}" || -z "${SNAP_DATA:-}" || -z "${SNAP_USER_DATA:-}" ]]; then
+	echo "Run inside the diode-node snap (connect backup-dir first):" >&2
+	echo "  sudo snap connect diode-node:backup-dir" >&2
+	echo "  sudo snap run --shell diode-node -c 'bin/restore_snap_backup <backup.tar.gz>'" >&2
+	exit 1
+fi
+
+umask 077
+staging_dir=$(mktemp -d)
+trap 'rm -rf "$staging_dir"' EXIT
+
+tar -xzf "$backup_file" -C "$staging_dir"
+
+if [[ -d "$staging_dir/snap_user_data" ]]; then
+	mkdir -p "$SNAP_USER_DATA"
+	cp -a "$staging_dir/snap_user_data/." "$SNAP_USER_DATA/"
+fi
+
+if [[ -d "$staging_dir/snap_data" ]]; then
+	mkdir -p "$SNAP_DATA"
+	cp -a "$staging_dir/snap_data/." "$SNAP_DATA/"
+fi
+
+echo "Restored backup into $SNAP_DATA and $SNAP_USER_DATA"

scripts/snap_backup_on_remove.sh

@@ -0,0 +1,101 @@
+#!/bin/bash
+# Automatic wallet backup when the diode-node snap is removed.
+# Invoked from snap/hooks/remove; BACKUP_DIR can be overridden for tests.
+set -euo pipefail
+
+BACKUP_DIR="${BACKUP_DIR:-/var/backups/diode-node}"
+SNAP_NAME="${SNAP_NAME:-diode-node}"
+staging_dir=""
+
+log() {
+	echo "diode-node remove hook: $*" >&2
+}
+
+stage_critical_files() {
+	local snap_data="$1"
+	local snap_user_data="$2"
+	local staging_dir="$3"
+	local has_data=0
+
+	if [[ -f "$snap_user_data/node" ]]; then
+		mkdir -p "$staging_dir/snap_user_data"
+		cp "$snap_user_data/node" "$staging_dir/snap_user_data/"
+		has_data=1
+	fi
+
+	if [[ -d "$snap_data" ]]; then
+		for nodedata in "$snap_data"/nodedata_*; do
+			if [[ -d "$nodedata" ]]; then
+				mkdir -p "$staging_dir/snap_data"
+				cp -a "$nodedata" "$staging_dir/snap_data/"
+				has_data=1
+			fi
+		done
+	fi
+
+	echo "$has_data"
+}
+
+write_manifest() {
+	local staging_dir="$1"
+	local snap_data="$2"
+	local snap_user_data="$3"
+
+	cat >"$staging_dir/manifest.txt" <<EOF
+diode-node automatic backup
+created: $(date -u +%Y-%m-%dT%H:%M:%SZ)
+snap: ${SNAP_NAME}
+snap_data: ${snap_data}
+snap_user_data: ${snap_user_data}
+
+Restore with bin/restore_snap_backup after reinstalling the snap
+(connect backup-dir: sudo snap connect diode-node:backup-dir).
+If this backup is missing, use "snap saved" within 31 days of removal.
+EOF
+}
+
+main() {
+	umask 077
+	local snap_data="${SNAP_DATA:-}"
+	local snap_user_data="${SNAP_USER_DATA:-}"
+
+	if [[ -z "$snap_data" || -z "$snap_user_data" ]]; then
+		log "SNAP_DATA or SNAP_USER_DATA not set, skipping backup"
+		exit 0
+	fi
+
+	staging_dir=$(mktemp -d)
+	trap '[[ -n "$staging_dir" ]] && rm -rf "$staging_dir"' EXIT
+
+	local has_data
+	has_data=$(stage_critical_files "$snap_data" "$snap_user_data" "$staging_dir")
+
+	if [[ "$has_data" -eq 0 ]]; then
+		log "no critical node data found, skipping backup"
+		exit 0
+	fi
+
+	write_manifest "$staging_dir" "$snap_data" "$snap_user_data"
+
+	if ! mkdir -p "$BACKUP_DIR" 2>/dev/null; then
+		log "cannot create backup directory $BACKUP_DIR (is backup-dir plug connected?)"
+		log "use 'snap saved' within 31 days to recover data via 'snap restore'"
+		exit 0
+	fi
+	chmod 0700 "$BACKUP_DIR" 2>/dev/null || true
+
+	local timestamp backup_file
+	timestamp=$(date -u +%Y-%m-%d_%H%M%S)
+	backup_file="$BACKUP_DIR/diode_node_backup_${timestamp}.tar.gz"
+
+	if ! tar -czf "$backup_file" -C "$staging_dir" .; then
+		log "failed to write backup archive to $backup_file"
+		exit 0
+	fi
+
+	chmod 0600 "$backup_file"
+
+	log "wallet backup saved to $backup_file"
+}
+
+main "$@"

snap/Makefile

@@ -8,6 +8,12 @@ install:
 	mkdir -p $(DESTDIR)/meta/hooks
 	cp snap/configure $(DESTDIR)/meta/hooks/
 	chmod +x $(DESTDIR)/meta/hooks/configure
+	cp snap/hooks/remove $(DESTDIR)/meta/hooks/remove
+	chmod +x $(DESTDIR)/meta/hooks/remove
 	tar -x --no-same-owner -zf _build/prod/diode_node-`./scripts/version.sh`.tar.gz -C $(DESTDIR)
 	cp snap/run $(DESTDIR)/bin/
 	chmod +x $(DESTDIR)/bin/run
+	cp scripts/snap_backup_on_remove.sh $(DESTDIR)/bin/backup_on_remove
+	chmod +x $(DESTDIR)/bin/backup_on_remove
+	cp scripts/restore_snap_backup.sh $(DESTDIR)/bin/restore_snap_backup
+	chmod +x $(DESTDIR)/bin/restore_snap_backup

snap/hooks/remove

@@ -0,0 +1,3 @@
+#!/bin/sh
+# Runs before snap data is deleted. See scripts/snap_backup_on_remove.sh.
+exec "$SNAP/bin/backup_on_remove"

snap/snapcraft.yaml

@@ -28,6 +28,16 @@ lint:
     - metadata:
         - donation
 
+plugs:
+  backup-dir:
+    interface: system-files
+    write:
+      - /var/backups/diode-node
+
+hooks:
+  remove:
+    plugs: [backup-dir]
+
 parts:
   diode-node:
     # See 'snapcraft plugins'
@@ -77,7 +87,7 @@ apps:
 
   shell:
     command: bin/run elevated remote
-    plugs: [network, network-bind]
+    plugs: [network, network-bind, backup-dir]
 
   rpc:
     command: bin/run elevated rpc

test/snap_backup_on_remove_test.exs

@@ -0,0 +1,120 @@
+defmodule SnapBackupOnRemoveTest do
+  use ExUnit.Case, async: true
+
+  @script Path.expand("../scripts/snap_backup_on_remove.sh", __DIR__)
+
+  setup do
+    root = Path.join(System.tmp_dir!(), "snap_backup_test_#{System.unique_integer([:positive])}")
+    snap_data = Path.join(root, "snap_data")
+    snap_user_data = Path.join(root, "snap_user_data")
+    backup_dir = Path.join(root, "backups")
+    extract_dir = Path.join(root, "extract")
+
+    on_exit(fn -> File.rm_rf!(root) end)
+
+    %{
+      root: root,
+      snap_data: snap_data,
+      snap_user_data: snap_user_data,
+      backup_dir: backup_dir,
+      extract_dir: extract_dir
+    }
+  end
+
+  defp run_backup(context) do
+    env = [
+      {"SNAP_DATA", context.snap_data},
+      {"SNAP_USER_DATA", context.snap_user_data},
+      {"SNAP_NAME", "diode-node"},
+      {"BACKUP_DIR", context.backup_dir}
+    ]
+
+    System.cmd("bash", [@script], env: env, stderr_to_stdout: true)
+  end
+
+  test "creates tarball with node identity and nodedata", context do
+    File.mkdir_p!(Path.join(context.snap_data, "nodedata_prod"))
+    File.mkdir_p!(context.snap_user_data)
+
+    File.write!(Path.join(context.snap_user_data, "node"), "diode_node@host.diode\n")
+    File.write!(Path.join(context.snap_data, "nodedata_prod/wallet.dat"), "wallet-secrets")
+
+    {output, 0} = run_backup(context)
+    assert output =~ "wallet backup saved"
+
+    [backup_name] = File.ls!(context.backup_dir)
+    assert backup_name =~ ~r/^diode_node_backup_.*\.tar\.gz$/
+
+    backup_path = Path.join(context.backup_dir, backup_name)
+    assert File.stat!(backup_path).mode &&& 0o777 == 0o600
+    assert File.stat!(context.backup_dir).mode &&& 0o777 == 0o700
+
+    File.mkdir_p!(context.extract_dir)
+
+    {_, 0} =
+      System.cmd("tar", ["-xzf", backup_path, "-C", context.extract_dir], stderr_to_stdout: true)
+
+    assert File.read!(Path.join(context.extract_dir, "snap_user_data/node")) ==
+             "diode_node@host.diode\n"
+
+    assert File.read!(Path.join(context.extract_dir, "snap_data/nodedata_prod/wallet.dat")) ==
+             "wallet-secrets"
+
+    manifest = File.read!(Path.join(context.extract_dir, "manifest.txt"))
+    assert manifest =~ "diode-node automatic backup"
+    assert manifest =~ context.snap_data
+  end
+
+  test "does not backup erl_inetrc even when present", context do
+    File.mkdir_p!(Path.join(context.snap_data, "nodedata_prod"))
+    File.mkdir_p!(context.snap_user_data)
+
+    File.write!(Path.join(context.snap_user_data, "node"), "diode_node@host.diode\n")
+
+    File.write!(
+      Path.join(context.snap_user_data, "erl_inetrc"),
+      "{host, {127,0,0,1}, [\"host.diode\", \"diode_node@host.diode\"]}.\n"
+    )
+
+    File.write!(Path.join(context.snap_data, "nodedata_prod/wallet.dat"), "wallet-secrets")
+
+    {output, 0} = run_backup(context)
+    assert output =~ "wallet backup saved"
+
+    [backup_name] = File.ls!(context.backup_dir)
+    backup_path = Path.join(context.backup_dir, backup_name)
+    File.mkdir_p!(context.extract_dir)
+
+    {_, 0} =
+      System.cmd("tar", ["-xzf", backup_path, "-C", context.extract_dir], stderr_to_stdout: true)
+
+    refute File.exists?(Path.join(context.extract_dir, "snap_user_data/erl_inetrc"))
+  end
+
+  test "skips backup when no critical data exists", context do
+    File.mkdir_p!(context.snap_data)
+    File.mkdir_p!(context.snap_user_data)
+
+    {output, 0} = run_backup(context)
+    assert output =~ "no critical node data found"
+    refute File.exists?(context.backup_dir)
+  end
+
+  test "does not fail removal when backup directory is not writable", context do
+    File.mkdir_p!(context.snap_user_data)
+    File.write!(Path.join(context.snap_user_data, "node"), "diode_node@test.diode\n")
+
+    env = [
+      {"SNAP_DATA", context.snap_data},
+      {"SNAP_USER_DATA", context.snap_user_data},
+      {"SNAP_NAME", "diode-node"},
+      {"BACKUP_DIR", "/root/diode-node-backup-should-not-exist"}
+    ]
+
+    {output, 0} =
+      System.cmd("bash", [@script], env: env, stderr_to_stdout: true)
+
+    assert output =~ "cannot create backup directory"
+    assert output =~ "snap saved"
+  end
+end