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infrastructure/databases/database-backups/SKILL.md

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+---
+name: database-backups
+description: Implement database backup strategies. Configure automated backups, retention, and recovery testing. Use when designing backup and recovery procedures.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# Database Backups
+
+Implement comprehensive database backup strategies.
+
+## Backup Types
+
+```yaml
+backup_types:
+  full:
+    description: Complete database copy
+    frequency: Weekly
+    
+  incremental:
+    description: Changes since last backup
+    frequency: Daily
+    
+  transaction_log:
+    description: Continuous transaction logging
+    frequency: Continuous
+```
+
+## Automated Backup Script
+
+```bash
+#!/bin/bash
+DATE=$(date +%Y%m%d_%H%M%S)
+BACKUP_DIR="/backups"
+
+# PostgreSQL
+pg_dump -Fc mydb > $BACKUP_DIR/pg_$DATE.dump
+
+# MySQL
+mysqldump -u root -p$MYSQL_PWD mydb | gzip > $BACKUP_DIR/mysql_$DATE.sql.gz
+
+# Upload to S3
+aws s3 cp $BACKUP_DIR/pg_$DATE.dump s3://backups/postgres/
+
+# Cleanup old backups (keep 7 days)
+find $BACKUP_DIR -name "*.dump" -mtime +7 -delete
+```
+
+## Recovery Testing
+
+```bash
+# Create test environment
+docker run -d --name restore-test postgres:15
+
+# Restore backup
+pg_restore -d testdb backup.dump
+
+# Verify data integrity
+psql testdb -c "SELECT COUNT(*) FROM users;"
+```
+
+## Best Practices
+
+- 3-2-1 Rule: 3 copies, 2 media types, 1 offsite
+- Regular recovery testing
+- Encrypt backups at rest
+- Monitor backup success
+- Document recovery procedures

infrastructure/databases/mongodb/SKILL.md

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+---
+name: mongodb
+description: Administer MongoDB databases. Configure replica sets, sharding, and backups. Use when managing MongoDB deployments.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# MongoDB
+
+Administer MongoDB NoSQL databases.
+
+## Installation & Setup
+
+```bash
+# Install
+apt install mongodb-org
+
+# Start service
+systemctl start mongod
+
+# Connect
+mongosh
+
+# Create user
+use admin
+db.createUser({
+  user: "admin",
+  pwd: "secret",
+  roles: ["root"]
+})
+```
+
+## Basic Operations
+
+```javascript
+// Create database and collection
+use mydb
+db.users.insertOne({ name: "John", email: "john@example.com" })
+
+// Query
+db.users.find({ name: "John" })
+db.users.find().sort({ name: 1 }).limit(10)
+
+// Index
+db.users.createIndex({ email: 1 }, { unique: true })
+```
+
+## Replica Set
+
+```javascript
+// Initialize replica set
+rs.initiate({
+  _id: "myReplicaSet",
+  members: [
+    { _id: 0, host: "mongo1:27017" },
+    { _id: 1, host: "mongo2:27017" },
+    { _id: 2, host: "mongo3:27017" }
+  ]
+})
+```
+
+## Backup
+
+```bash
+# Backup
+mongodump --out /backup/
+
+# Restore
+mongorestore /backup/
+```
+
+## Best Practices
+
+- Use replica sets in production
+- Implement proper indexing
+- Enable authentication
+- Regular backups with mongodump

infrastructure/databases/mysql/SKILL.md

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+---
+name: mysql
+description: Administer MySQL/MariaDB databases. Configure replication and optimize performance. Use when managing MySQL deployments.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# MySQL / MariaDB
+
+Administer MySQL and MariaDB databases.
+
+## Installation & Setup
+
+```bash
+# Install
+apt install mysql-server
+
+# Secure installation
+mysql_secure_installation
+
+# Access
+mysql -u root -p
+
+# Create database and user
+CREATE DATABASE mydb;
+CREATE USER 'myapp'@'%' IDENTIFIED BY 'secret';
+GRANT ALL PRIVILEGES ON mydb.* TO 'myapp'@'%';
+FLUSH PRIVILEGES;
+```
+
+## Configuration
+
+```bash
+# /etc/mysql/mysql.conf.d/mysqld.cnf
+[mysqld]
+innodb_buffer_pool_size = 1G
+max_connections = 200
+slow_query_log = 1
+long_query_time = 2
+```
+
+## Backup & Restore
+
+```bash
+# Backup
+mysqldump -u root -p mydb > backup.sql
+mysqldump -u root -p --all-databases > full_backup.sql
+
+# Restore
+mysql -u root -p mydb < backup.sql
+```
+
+## Replication
+
+```bash
+# Primary
+[mysqld]
+server-id = 1
+log_bin = mysql-bin
+
+# Replica
+CHANGE MASTER TO
+  MASTER_HOST='primary',
+  MASTER_USER='replicator',
+  MASTER_PASSWORD='secret',
+  MASTER_LOG_FILE='mysql-bin.000001',
+  MASTER_LOG_POS=0;
+START SLAVE;
+```
+
+## Best Practices
+
+- Enable slow query logging
+- Use InnoDB storage engine
+- Regular backups with mysqldump
+- Monitor with SHOW PROCESSLIST

infrastructure/databases/postgresql/SKILL.md

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+---
+name: postgresql
+description: Administer PostgreSQL databases. Configure replication, backups, and performance tuning. Use when managing PostgreSQL deployments.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# PostgreSQL
+
+Administer and optimize PostgreSQL databases.
+
+## Installation & Setup
+
+```bash
+# Install
+apt install postgresql postgresql-contrib
+
+# Access
+sudo -u postgres psql
+
+# Create database and user
+CREATE USER myapp WITH PASSWORD 'secret';
+CREATE DATABASE mydb OWNER myapp;
+GRANT ALL PRIVILEGES ON DATABASE mydb TO myapp;
+```
+
+## Configuration
+
+```bash
+# /etc/postgresql/15/main/postgresql.conf
+max_connections = 200
+shared_buffers = 256MB
+effective_cache_size = 768MB
+work_mem = 4MB
+maintenance_work_mem = 64MB
+```
+
+## Backup & Restore
+
+```bash
+# Backup
+pg_dump mydb > backup.sql
+pg_dump -Fc mydb > backup.dump  # Custom format
+
+# Restore
+psql mydb < backup.sql
+pg_restore -d mydb backup.dump
+```
+
+## Replication
+
+```bash
+# Primary
+ALTER SYSTEM SET wal_level = replica;
+CREATE USER replicator REPLICATION LOGIN PASSWORD 'secret';
+
+# Replica
+pg_basebackup -h primary -U replicator -D /var/lib/postgresql/15/main -P
+```
+
+## Best Practices
+
+- Regular VACUUM and ANALYZE
+- Monitor slow queries
+- Implement connection pooling (PgBouncer)
+- Regular backups with pg_dump or pg_basebackup

infrastructure/databases/redis/SKILL.md

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+---
+name: redis
+description: Configure Redis for caching and data storage. Set up clustering, persistence, and Sentinel. Use when implementing Redis caching or queues.
+license: MIT
+metadata:
+  author: devops-skills
+  version: "1.0"
+---
+
+# Redis
+
+Configure Redis for caching and data storage.
+
+## Installation & Setup
+
+```bash
+# Install
+apt install redis-server
+
+# Configuration
+# /etc/redis/redis.conf
+bind 0.0.0.0
+protected-mode yes
+requirepass yourpassword
+maxmemory 256mb
+maxmemory-policy allkeys-lru
+```
+
+## Basic Operations
+
+```bash
+redis-cli -a yourpassword
+
+# String operations
+SET key "value"
+GET key
+SETEX key 3600 "value"  # With TTL
+
+# Hash
+HSET user:1 name "John" email "john@example.com"
+HGETALL user:1
+
+# List
+LPUSH queue "task1"
+RPOP queue
+```
+
+## Persistence
+
+```bash
+# RDB (snapshot)
+save 900 1
+save 300 10
+
+# AOF (append-only file)
+appendonly yes
+appendfsync everysec
+```
+
+## Sentinel (HA)
+
+```bash
+# sentinel.conf
+sentinel monitor mymaster 10.0.0.1 6379 2
+sentinel down-after-milliseconds mymaster 30000
+sentinel failover-timeout mymaster 180000
+```
+
+## Best Practices
+
+- Set maxmemory and eviction policy
+- Use persistence for critical data
+- Implement Sentinel for HA
+- Monitor memory usage