List udev/fstab rules to preserve device mapping after migrations

Signed-off-by: Tapas Sharma <tapas@platform9.com>

Author: sharma-tapas

scripts/generate-mount-persistence.sh

@@ -0,0 +1,91 @@
+#!/usr/bin/env bash
+# generate-mount-persistence.sh
+#
+# Prints:
+#   1. udev rules that bind each currently mounted real block device (under /dev)
+#      to a stable symlink under /dev/disk/by-mountpoint/<sanitized-mount-path>.
+#   2. Equivalent /etc/fstab entries with UUID=<uuid>.
+#
+# Supported distros: CentOS 6/7/8, Rocky Linux, Ubuntu, SUSE, RHEL.
+#
+# Usage:
+#   sudo bash generate-mount-persistence.sh > output.txt
+#   # Review output.txt for udev rules + suggested fstab entries.
+
+set -euo pipefail
+
+command -v blkid >/dev/null 2>&1 || {
+  echo "Error: blkid not found. Please install util-linux." >&2
+  exit 1
+}
+
+SKIP_FS_TYPES="^(autofs|bpf|cgroup|cgroup2|configfs|debugfs|devpts|devtmpfs|efivarfs|fusectl|fuse\.overlayfs|hugetlbfs|mqueue|nsfs|overlay|proc|pstore|ramfs|rpc_pipefs|securityfs|selinuxfs|smb3?|squashfs|sysfs|tmpfs|tracefs)$"
+SKIP_DEVICES_REGEX="^/dev/(ram|loop|fd|sr|zram|nbd|md|pmem)[0-9]"
+
+UDEV_RULES=""
+FSTAB_LINES=""
+
+awk '
+  {
+    src=$1; tgt=$2; fstype=$3;
+    gsub(/\\040/, " ", tgt);
+    gsub(/\\011/, "\t", tgt);
+    gsub(/\\012/, "\n", tgt);
+    print src "\t" tgt "\t" fstype;
+  }
+' /proc/mounts | while IFS=$'\t' read -r SRC TGT FST; do
+  [[ "$SRC" == /dev/* ]] || continue
+  if [[ "$FST" =~ $SKIP_FS_TYPES ]]; then
+    continue
+  fi
+  if [[ "$SRC" =~ $SKIP_DEVICES_REGEX ]]; then
+    continue
+  fi
+
+  UUID="$(blkid -s UUID -o value -- "$SRC" 2>/dev/null || true)"
+  if [[ -z "$UUID" ]] && command -v lsblk >/dev/null 2>&1; then
+    UUID="$(lsblk -no UUID -- "$SRC" 2>/dev/null | head -n1 || true)"
+  fi
+  [[ -z "$UUID" ]] && continue
+
+  SAFE_NAME="$TGT"
+  if [[ "$SAFE_NAME" == "/" ]]; then
+    SAFE_NAME="root"
+  else
+    SAFE_NAME="${SAFE_NAME#/}"
+    SAFE_NAME="${SAFE_NAME//\//_}"
+    SAFE_NAME="${SAFE_NAME// /_}"
+  fi
+
+  # Udev rules
+  echo "ACTION==\"add\", SUBSYSTEM==\"block\", ENV{ID_FS_UUID}==\"$UUID\", SYMLINK+=\"disk/by-mountpoint/$SAFE_NAME\""
+  echo "ACTION==\"change\", SUBSYSTEM==\"block\", ENV{ID_FS_UUID}==\"$UUID\", SYMLINK+=\"disk/by-mountpoint/$SAFE_NAME\""
+
+  # /etc/fstab entry suggestion
+  # Extract mount options from /proc/mounts
+  OPTIONS="$(awk -v src="$SRC" '$1==src {print $4}' /proc/mounts | head -n1)"
+  OPTIONS="${OPTIONS:-defaults}"
+
+  # Pass and dump values: root usually 1 1, others 0 2
+  if [[ "$TGT" == "/" ]]; then
+    DUMP_PASS="1 1"
+  else
+    DUMP_PASS="0 2"
+  fi
+
+  echo "FSTAB: UUID=$UUID  $TGT  $FST  $OPTIONS  $DUMP_PASS"
+done | awk '
+  BEGIN {
+    print "# === UDEV RULES (save to /etc/udev/rules.d/99-by-mountpoint.rules) ==="
+  }
+  /^ACTION/ { print; next }
+  /^FSTAB:/ {
+    fstab_line = substr($0, 7)
+    if (!printed_fstab) {
+      print ""
+      print "# === /etc/fstab entries (append to /etc/fstab) ==="
+      printed_fstab=1
+    }
+    print fstab_line
+  }
+'