improve backup script preflight checks and file size validation

scripts/backup.sh

@@ -1,13 +1,19 @@
 #!/usr/bin/env bash
 # =====================================================================
 # WebGIS Database Backup Script
-# Location: /opt/webgis-lohne/scripts/backup.sh (on server)
+# Location: /opt/webgis-lohne/scripts/backup.sh (on Server)
-# Purpose:  Creates compressed pg_dump backups with daily/weekly/monthly
+# Purpose:  Creates compressed pg_dump Backups with daily/weekly/monthly
-#           rotation. Intended to be run via cron.
+#           Rotation. Intended to be run via Cron.
 # =====================================================================
 
+
+# Safety Switches
 set -euo pipefail
 
+# Logs Error Messages
+trap 'echo "[$(date)] ERROR: Script failed at Line ${LINENO} with Exit Code $?."' ERR
+
+
 # ---------------------------------------------------------------------
 # Configuration
 # ---------------------------------------------------------------------
@@ -16,21 +22,49 @@ DB_PORT="5432"
 DB_NAME="webgis-db"
 DB_USER="webgis-db-admin"
 
+
 BACKUP_ROOT="/var/backups/webgis"
 BACKUP_DIR_DAILY="${BACKUP_ROOT}/daily"
 BACKUP_DIR_WEEKLY="${BACKUP_ROOT}/weekly"
 BACKUP_DIR_MONTHLY="${BACKUP_ROOT}/monthly"
 
-# Retention Periods (in days)
+# Retention Periods in Days
 KEEP_DAILY=7
 KEEP_WEEKLY=28
 KEEP_MONTHLY=365
 
-# Password is read from a protected file (see setup instructions).
+# Minimum acceptable Backup File Size in Bytes
-# pg_dump honors the PGPASSFILE environment variable.
+# Valid Dumps of even empty Databases are several KBs
+MIN_BACKUP_SIZE=10000
+
+# Password is read from  protected File
+# pg_dump honors the PGPASSFILE Environment Variable.
 export PGPASSFILE="/root/.pgpass_webgis"
 
 
+# ---------------------------------------------------------------------
+# Preflight Checks
+# ---------------------------------------------------------------------
+
+# Check pg_dump Availability
+if ! command -v pg_dump &> /dev/null; then
+    echo "[$(date)] ERROR: pg_dump not found. Install postgresql-client."
+    exit 1
+fi
+
+# Check Password File Existence and Permissions
+if [[ ! -f "${PGPASSFILE}" ]]; then
+    echo "[$(date)] ERROR: Password File ${PGPASSFILE} not found."
+    exit 1
+fi
+
+PGPASS_PERMS=$(stat -c "%a" "${PGPASSFILE}")
+if [[ "${PGPASS_PERMS}" != "600" ]]; then
+    echo "[$(date)] ERROR: ${PGPASSFILE} has Permissions ${PGPASS_PERMS}, expected 600."
+    exit 1
+fi
+
+
 # ---------------------------------------------------------------------
 # Preparation
 # ---------------------------------------------------------------------
@@ -42,11 +76,11 @@ mkdir -p "${BACKUP_DIR_DAILY}" "${BACKUP_DIR_WEEKLY}" "${BACKUP_DIR_MONTHLY}"
 
 
 # ---------------------------------------------------------------------
-# Create Daily Backup (Custom-Format, compressed)
+# Create Daily Backup in compressed Custom Format
 # ---------------------------------------------------------------------
 DAILY_FILE="${BACKUP_DIR_DAILY}/webgis_${TIMESTAMP}.dump"
 
-echo "[$(date)] Starting daily backup -> ${DAILY_FILE}"
+echo "[$(date)] Starting daily Backup -> ${DAILY_FILE}"
 
 pg_dump \
     --host="${DB_HOST}" \
@@ -57,7 +91,14 @@ pg_dump \
     --file="${DAILY_FILE}" \
     "${DB_NAME}"
 
-echo "[$(date)] Daily backup complete."
+# Verify Backup File Size
+BACKUP_SIZE=$(stat -c "%s" "${DAILY_FILE}")
+if [[ "${BACKUP_SIZE}" -lt "${MIN_BACKUP_SIZE}" ]]; then
+    echo "[$(date)] ERROR: Backup File is only ${BACKUP_SIZE} Bytes (Minimum: ${MIN_BACKUP_SIZE}). Dump probably corrupt."
+    exit 1
+fi
+
+echo "[$(date)] Daily Backup complete (${BACKUP_SIZE} Bytes)."
 
 
 # ---------------------------------------------------------------------
@@ -65,7 +106,7 @@ echo "[$(date)] Daily backup complete."
 # ---------------------------------------------------------------------
 if [[ "${DAY_OF_WEEK}" == "7" ]]; then
     cp "${DAILY_FILE}" "${BACKUP_DIR_WEEKLY}/webgis_${TIMESTAMP}.dump"
-    echo "[$(date)] Promoted to weekly backup."
+    echo "[$(date)] Promoted to weekly Backup."
 fi
 
 
@@ -74,16 +115,15 @@ fi
 # ---------------------------------------------------------------------
 if [[ "${DAY_OF_MONTH}" == "01" ]]; then
     cp "${DAILY_FILE}" "${BACKUP_DIR_MONTHLY}/webgis_${TIMESTAMP}.dump"
-    echo "[$(date)] Promoted to monthly backup."
+    echo "[$(date)] Promoted to monthly Backup."
 fi
 
 
 # ---------------------------------------------------------------------
-# Rotation: Delete Backups Older than Retention Period
+# Rotation: Delete Backups older than Retention Period
 # ---------------------------------------------------------------------
 find "${BACKUP_DIR_DAILY}"   -name "*.dump" -mtime +${KEEP_DAILY}   -delete
 find "${BACKUP_DIR_WEEKLY}"  -name "*.dump" -mtime +${KEEP_WEEKLY}  -delete
 find "${BACKUP_DIR_MONTHLY}" -name "*.dump" -mtime +${KEEP_MONTHLY} -delete
 
-
+echo "[$(date)] Backup Rotation complete."
-echo "[$(date)] Backup rotation complete."