database-backups（数据库备份）

Database Backups

Implement comprehensive, automated database backup strategies with tested recovery procedures.

When to Use

• You are deploying a new database and need a backup plan from day one.
• You need to automate nightly or hourly backups for PostgreSQL, MySQL, or MongoDB.
• You want to ship backups to S3-compatible object storage with retention policies.
• You are building or verifying disaster recovery runbooks.

Prerequisites

• Database client tools installed (pg_dump, mysqldump, mongodump).
• AWS CLI or restic for remote storage.
• cron or systemd timers for scheduling.
• An S3 bucket (or S3-compatible endpoint) for offsite backups.

Backup Types

PostgreSQL Backups

Logical Backup with pg_dump

#!/bin/bash
# pg_backup.sh — PostgreSQL logical backup
set -euo pipefail

DB_NAME="mydb"
DB_USER="backup_user"
DB_HOST="localhost"
BACKUP_DIR="/backups/postgres"
DATE=$(date +%Y%m%d_%H%M%S)
FILENAME="${BACKUP_DIR}/${DB_NAME}_${DATE}.dump"

mkdir -p "$BACKUP_DIR"

# Custom compressed format (recommended for selective restore)
pg_dump -h "$DB_HOST" -U "$DB_USER" -Fc -Z6 "$DB_NAME" > "$FILENAME"

echo "[$(date)] PostgreSQL backup complete: $FILENAME ($(du -h "$FILENAME" | cut -f1))"

Physical Backup with pg_basebackup

#!/bin/bash
# pg_basebackup.sh — PostgreSQL physical backup for PITR
set -euo pipefail

BACKUP_DIR="/backups/postgres/base_$(date +%Y%m%d)"
mkdir -p "$BACKUP_DIR"

pg_basebackup \
  -h localhost \
  -U replicator \
  -D "$BACKUP_DIR" \
  --wal-method=stream \
  --checkpoint=fast \
  --progress \
  --verbose

echo "[$(date)] Base backup complete: $BACKUP_DIR"

PostgreSQL Restore

# Restore from custom-format dump
pg_restore -h localhost -U myapp -d mydb --clean --if-exists /backups/postgres/mydb_20250115_020000.dump

# Restore a single table
pg_restore -h localhost -U myapp -d mydb -t orders /backups/postgres/mydb_20250115_020000.dump

# Restore from plain SQL
psql -h localhost -U myapp -d mydb < /backups/postgres/mydb_20250115.sql

MySQL Backups

Logical Backup with mysqldump

#!/bin/bash
# mysql_backup.sh — MySQL logical backup
set -euo pipefail

DB_NAME="mydb"
DB_USER="backup_user"
DB_PASS="${MYSQL_BACKUP_PASSWORD}"
BACKUP_DIR="/backups/mysql"
DATE=$(date +%Y%m%d_%H%M%S)
FILENAME="${BACKUP_DIR}/${DB_NAME}_${DATE}.sql.gz"

mkdir -p "$BACKUP_DIR"

mysqldump -u "$DB_USER" -p"$DB_PASS" \
  --single-transaction \
  --routines \
  --triggers \
  --events \
  "$DB_NAME" | gzip > "$FILENAME"

echo "[$(date)] MySQL backup complete: $FILENAME ($(du -h "$FILENAME" | cut -f1))"

Physical Backup with Percona XtraBackup

#!/bin/bash
# xtrabackup.sh — MySQL physical backup
set -euo pipefail

BACKUP_DIR="/backups/mysql/full_$(date +%Y%m%d)"

xtrabackup --backup \
  --user=backup_user \
  --password="${MYSQL_BACKUP_PASSWORD}" \
  --target-dir="$BACKUP_DIR"

xtrabackup --prepare --target-dir="$BACKUP_DIR"

echo "[$(date)] XtraBackup complete: $BACKUP_DIR"

MySQL Restore

# Restore from compressed mysqldump
gunzip < /backups/mysql/mydb_20250115_020000.sql.gz | mysql -u root -p mydb

# Restore from XtraBackup
sudo systemctl stop mysql
sudo rm -rf /var/lib/mysql/*
xtrabackup --move-back --target-dir=/backups/mysql/full_20250115
sudo chown -R mysql:mysql /var/lib/mysql
sudo systemctl start mysql

MongoDB Backups

Logical Backup with mongodump

#!/bin/bash
# mongo_backup.sh — MongoDB backup
set -euo pipefail

MONGO_URI="mongodb://backup_user:${MONGO_BACKUP_PASSWORD}@localhost:27017"
BACKUP_DIR="/backups/mongodb"
DATE=$(date +%Y%m%d_%H%M%S)
TARGET="${BACKUP_DIR}/${DATE}"

mkdir -p "$BACKUP_DIR"

# Full backup with compression
mongodump --uri="$MONGO_URI" --gzip --out="$TARGET"

echo "[$(date)] MongoDB backup complete: $TARGET"

MongoDB Restore

# Restore all databases
mongorestore --uri="mongodb://admin:secret@localhost:27017" \
  --gzip --drop /backups/mongodb/20250115_020000/

# Restore a single database
mongorestore --uri="mongodb://admin:secret@localhost:27017" \
  --gzip --drop --db mydb /backups/mongodb/20250115_020000/mydb/

# Restore a single collection
mongorestore --uri="mongodb://admin:secret@localhost:27017" \
  --gzip --drop --db mydb --collection users \
  /backups/mongodb/20250115_020000/mydb/users.bson.gz

Upload to S3

#!/bin/bash
# s3_upload.sh — Upload backups to S3
set -euo pipefail

S3_BUCKET="s3://my-backups"
BACKUP_DIR="/backups"
DATE=$(date +%Y%m%d)

# Upload PostgreSQL backup
aws s3 cp "${BACKUP_DIR}/postgres/" "${S3_BUCKET}/postgres/${DATE}/" \
  --recursive --storage-class STANDARD_IA \
  --sse AES256

# Upload MySQL backup
aws s3 cp "${BACKUP_DIR}/mysql/" "${S3_BUCKET}/mysql/${DATE}/" \
  --recursive --storage-class STANDARD_IA \
  --sse AES256

# Upload MongoDB backup
aws s3 cp "${BACKUP_DIR}/mongodb/" "${S3_BUCKET}/mongodb/${DATE}/" \
  --recursive --storage-class STANDARD_IA \
  --sse AES256

echo "[$(date)] S3 upload complete for ${DATE}"

S3 Lifecycle Policy for Retention

{
  "Rules": [
    {
      "ID": "BackupRetention",
      "Status": "Enabled",
      "Filter": { "Prefix": "" },
      "Transitions": [
        { "Days": 30, "StorageClass": "GLACIER" }
      ],
      "Expiration": { "Days": 365 }
    }
  ]
}

aws s3api put-bucket-lifecycle-configuration \
  --bucket my-backups \
  --lifecycle-configuration file://lifecycle.json

Restic Backup (Encrypted, Deduplicated)

# Initialize a restic repository on S3
export AWS_ACCESS_KEY_ID="AKIA..."
export AWS_SECRET_ACCESS_KEY="..."
export RESTIC_PASSWORD="strong_encryption_password"
export RESTIC_REPOSITORY="s3:s3.amazonaws.com/my-backups-restic"

restic init

# Backup the local backup directory
restic backup /backups/postgres /backups/mysql /backups/mongodb

# List snapshots
restic snapshots

# Prune old snapshots — keep 7 daily, 4 weekly, 6 monthly
restic forget --keep-daily 7 --keep-weekly 4 --keep-monthly 6 --prune

# Restore a snapshot
restic restore latest --target /restore/

Cron Schedules

# /etc/cron.d/db-backups

# PostgreSQL: nightly at 02:00
0 2 * * * backup /opt/scripts/pg_backup.sh >> /var/log/backup-pg.log 2>&1

# MySQL: nightly at 02:30
30 2 * * * backup /opt/scripts/mysql_backup.sh >> /var/log/backup-mysql.log 2>&1

# MongoDB: nightly at 03:00
0 3 * * * backup /opt/scripts/mongo_backup.sh >> /var/log/backup-mongo.log 2>&1

# Upload to S3: daily at 04:00
0 4 * * * backup /opt/scripts/s3_upload.sh >> /var/log/backup-s3.log 2>&1

# Local cleanup: keep 7 days of local backups
0 5 * * * backup find /backups -type f -mtime +7 -delete >> /var/log/backup-cleanup.log 2>&1

# Restic prune: weekly on Sunday at 06:00
0 6 * * 0 backup /opt/scripts/restic_prune.sh >> /var/log/backup-restic.log 2>&1

Automated Recovery Testing

#!/bin/bash
# verify_backup.sh — weekly restore test
set -euo pipefail

BACKUP_FILE=$(ls -t /backups/postgres/mydb_*.dump | head -1)

echo "[$(date)] Starting backup verification with $BACKUP_FILE"

# Spin up a temporary PostgreSQL container
docker run -d --name pg-restore-test \
  -e POSTGRES_USER=testuser \
  -e POSTGRES_PASSWORD=testpass \
  -e POSTGRES_DB=testdb \
  postgres:16-alpine

# Wait for container to be ready
sleep 5
until docker exec pg-restore-test pg_isready -U testuser; do
  sleep 2
done

# Copy backup into container and restore
docker cp "$BACKUP_FILE" pg-restore-test:/tmp/backup.dump
docker exec pg-restore-test pg_restore -U testuser -d testdb --clean --if-exists /tmp/backup.dump

# Run verification queries
USERS_COUNT=$(docker exec pg-restore-test psql -U testuser -d testdb -tAc "SELECT COUNT(*) FROM users;")
ORDERS_COUNT=$(docker exec pg-restore-test psql -U testuser -d testdb -tAc "SELECT COUNT(*) FROM orders;")

echo "[$(date)] Verification: users=$USERS_COUNT, orders=$ORDERS_COUNT"

# Cleanup
docker rm -f pg-restore-test

# Alert on failure
if [ "$USERS_COUNT" -lt 1 ]; then
  echo "ALERT: Backup verification failed — users table is empty" >&2
  exit 1
fi

echo "[$(date)] Backup verification PASSED"

Unified Backup Script

#!/bin/bash
# backup_all.sh — unified backup orchestrator
set -euo pipefail

LOG="/var/log/backup-all.log"
ALERT_EMAIL="ops@example.com"
ERRORS=0

log() { echo "[$(date '+%F %T')] $*" | tee -a "$LOG"; }

run_backup() {
  local name="$1" script="$2"
  log "Starting $name backup..."
  if bash "$script" >> "$LOG" 2>&1; then
    log "$name backup succeeded."
  else
    log "ERROR: $name backup FAILED."
    ERRORS=$((ERRORS + 1))
  fi
}

run_backup "PostgreSQL" /opt/scripts/pg_backup.sh
run_backup "MySQL"      /opt/scripts/mysql_backup.sh
run_backup "MongoDB"    /opt/scripts/mongo_backup.sh
run_backup "S3 Upload"  /opt/scripts/s3_upload.sh

if [ "$ERRORS" -gt 0 ]; then
  log "Backup run completed with $ERRORS error(s). Sending alert."
  mail -s "BACKUP ALERT: $ERRORS failure(s)" "$ALERT_EMAIL" < "$LOG"
  exit 1
fi

log "All backups completed successfully."

Best Practices

• 3-2-1 Rule: Keep 3 copies of data, on 2 different media types, with 1 offsite.
• Encrypt backups at rest: Use restic (built-in encryption), AWS SSE, or gpg.
• Test restores regularly: A backup that has never been restored is not a backup.
• Monitor backup jobs: Alert immediately on any failure; do not rely on silent cron jobs.
• Document RTOs and RPOs: Define Recovery Time Objective and Recovery Point Objective for each database.
• Version your backup scripts: Store them in Git alongside your infrastructure code.
• Use --single-transaction: For MySQL and PostgreSQL logical backups to get a consistent snapshot.
• Separate backup credentials: Use a dedicated read-only database user for backups.

Troubleshooting

Related Skills

• postgresql - PostgreSQL administration and pg_dump details
• mysql - MySQL administration and mysqldump details
• mongodb - MongoDB administration and mongodump details
• redis - Redis RDB/AOF persistence and backup