Ubuntu Databases

Ubuntu Server 24.04 LTS — Database Administration

Companion skill to ubuntu-server-admin. For other workloads see: ubuntu-web-servers, ubuntu-docker-host, ubuntu-file-storage, ubuntu-network-infra, ubuntu-monitoring, ubuntu-ollama-nvidia.

1. PostgreSQL 16

Installation (Official Apt Repo)

sudo apt install -y curl ca-certificates
sudo install -d /usr/share/postgresql-common/pgdg
sudo curl -o /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc \
  --fail https://www.postgresql.org/media/keys/ACCC4CF8.asc
echo "deb [signed-by=/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc] \
  https://apt.postgresql.org/pub/repos/apt noble-pgdg main" \
  | sudo tee /etc/apt/sources.list.d/pgdg.list
sudo apt update && sudo apt install -y postgresql-16 postgresql-client-16

Key paths: config /etc/postgresql/16/main/postgresql.conf, auth /etc/postgresql/16/main/pg_hba.conf, data /var/lib/postgresql/16/main/, logs /var/log/postgresql/postgresql-16-main.log.

pg_hba.conf

local   all       postgres                    peer
local   all       all                         scram-sha-256
host    all       all        10.0.1.0/24      scram-sha-256
host    replication replicator 10.0.1.20/32   scram-sha-256
host    all       all        0.0.0.0/0        reject

Reload after edit: sudo systemctl reload postgresql

postgresql.conf Tuning (16 GB RAM / 4-core example)

listen_addresses = '*'
max_connections = 200
shared_buffers = 4GB              # ~25% of RAM
effective_cache_size = 12GB
work_mem = 32MB
maintenance_work_mem = 1GB
huge_pages = try
wal_level = replica
wal_buffers = 64MB
max_wal_size = 4GB
min_wal_size = 1GB
checkpoint_completion_target = 0.9
archive_mode = on
archive_command = 'cp %p /var/lib/postgresql/16/archive/%f'
random_page_cost = 1.1            # SSD (4.0 for HDD)
effective_io_concurrency = 200    # SSD (2 for HDD)
max_parallel_workers_per_gather = 2
max_parallel_workers = 4
log_min_duration_statement = 500  # ms
log_checkpoints = on
log_lock_waits = on

Restart for shared_buffers/max_connections/wal_level; reload for most others.

User/Role Management

-- As postgres superuser: sudo -u postgres psql
CREATE ROLE appuser WITH LOGIN PASSWORD 'StrongP@ss!2024' VALID UNTIL '2027-01-01';
CREATE ROLE readonly WITH LOGIN PASSWORD 'ReadP@ss!2024';
CREATE DATABASE myapp OWNER appuser ENCODING 'UTF8';
GRANT CONNECT ON DATABASE myapp TO readonly;
\c myapp
GRANT USAGE ON SCHEMA public TO readonly;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO readonly;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO readonly;
REVOKE CREATE ON SCHEMA public FROM PUBLIC;

Backup — pg_dump / pg_restore

sudo -u postgres pg_dump -Fc myapp -f /backup/pg/myapp_$(date +%Y%m%d).dump    # custom format
sudo -u postgres pg_dumpall > /backup/pg/all_$(date +%Y%m%d).sql               # all databases
sudo -u postgres pg_restore -d myapp -j 4 --clean --if-exists /backup/pg/myapp.dump  # restore

Streaming Replication

Primary: create replication user, ensure wal_level = replica and pg_hba allows standby.

sudo -u postgres psql -c "CREATE ROLE replicator WITH REPLICATION LOGIN PASSWORD 'ReplP@ss!2024';"

Standby: stop PG, clear data dir, base backup with -R flag, start.

sudo systemctl stop postgresql
sudo rm -rf /var/lib/postgresql/16/main/*
sudo -u postgres pg_basebackup -h 10.0.1.10 -U replicator -D /var/lib/postgresql/16/main -Fp -Xs -P -R
sudo systemctl start postgresql

Verify: SELECT client_addr, state, replay_lsn FROM pg_stat_replication; (primary), SELECT pg_is_in_recovery(); (standby).

PgBouncer Connection Pooling

sudo apt install -y pgbouncer

/etc/pgbouncer/pgbouncer.ini:

[databases]
myapp = host=127.0.0.1 port=5432 dbname=myapp
[pgbouncer]
listen_addr = 0.0.0.0
listen_port = 6432
auth_type = scram-sha-256
auth_file = /etc/pgbouncer/userlist.txt
pool_mode = transaction
default_pool_size = 25
max_client_conn = 500

Generate userlist from PG: sudo -u postgres psql -tAc "SELECT '\"'||rolname||'\" \"'||rolpassword||'\"' FROM pg_authid WHERE rolcanlogin" > /etc/pgbouncer/userlist.txt

pg_stat Monitoring

SELECT pid, usename, state, query FROM pg_stat_activity WHERE state != 'idle';
SELECT relname, n_dead_tup, last_autovacuum FROM pg_stat_user_tables ORDER BY n_dead_tup DESC LIMIT 10;
SELECT round(100.0*sum(blks_hit)/nullif(sum(blks_hit)+sum(blks_read),0),2) AS cache_pct FROM pg_stat_database;
-- Requires shared_preload_libraries = 'pg_stat_statements'
SELECT query, calls, mean_exec_time::numeric(10,2) FROM pg_stat_statements ORDER BY total_exec_time DESC LIMIT 10;
SELECT client_addr, pg_wal_lsn_diff(pg_current_wal_lsn(), replay_lsn) AS lag_bytes FROM pg_stat_replication;

2. MySQL 8 / MariaDB

Installation

# MySQL 8 (from default Ubuntu repos)
sudo apt install -y mysql-server && sudo systemctl enable --now mysql
sudo mysql_secure_installation

# MariaDB (alternative)
sudo apt install -y mariadb-server && sudo systemctl enable --now mariadb
sudo mariadb-secure-installation

my.cnf Tuning (16 GB / 4-core)

Drop-in: /etc/mysql/mysql.conf.d/99-tuning.cnf

[mysqld]
innodb_buffer_pool_size = 11G     # ~70% RAM for dedicated DB
innodb_buffer_pool_instances = 8
innodb_log_file_size = 1G
innodb_flush_log_at_trx_commit = 1
innodb_flush_method = O_DIRECT
innodb_io_capacity = 2000
max_connections = 300
log_bin = /var/log/mysql/mysql-bin
binlog_expire_logs_seconds = 604800
binlog_format = ROW
sync_binlog = 1
server_id = 1
slow_query_log = 1
slow_query_log_file = /var/log/mysql/mysql-slow.log
long_query_time = 1
character_set_server = utf8mb4

User Management

CREATE USER 'appuser'@'10.0.1.%' IDENTIFIED BY 'StrongP@ss!2024';
GRANT SELECT, INSERT, UPDATE, DELETE ON myapp.* TO 'appuser'@'10.0.1.%';
CREATE USER 'readonly'@'10.0.1.%' IDENTIFIED BY 'ReadP@ss!2024';
GRANT SELECT ON myapp.* TO 'readonly'@'10.0.1.%';
FLUSH PRIVILEGES;

Backup — mysqldump

mysqldump -u root --single-transaction --routines --triggers myapp | gzip > /backup/mysql/myapp_$(date +%Y%m%d).sql.gz
mysql -u root myapp < /backup/mysql/myapp.sql   # restore

Replication (Source / Replica)

Source: enable log_bin, server_id=1, create replicator user with REPLICATION SLAVE.

Replica: set server_id=2, then:

CHANGE REPLICATION SOURCE TO SOURCE_HOST='10.0.1.10', SOURCE_USER='replicator',
  SOURCE_PASSWORD='ReplP@ss!2024', SOURCE_LOG_FILE='mysql-bin.000001', SOURCE_LOG_POS=154;
START REPLICA;
SHOW REPLICA STATUS\G   -- check Replica_IO_Running=Yes, Replica_SQL_Running=Yes

Slow Query Analysis

mysqldumpslow -s t -t 10 /var/log/mysql/mysql-slow.log
# Or: sudo apt install -y percona-toolkit && pt-query-digest /var/log/mysql/mysql-slow.log

3. Redis 7

Installation (Official Repo)

curl -fsSL https://packages.redis.io/gpg | sudo gpg --dearmor -o /usr/share/keyrings/redis-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/redis-archive-keyring.gpg] https://packages.redis.io/deb noble main" \
  | sudo tee /etc/apt/sources.list.d/redis.list
sudo apt update && sudo apt install -y redis-server
sudo systemctl enable --now redis-server

redis.conf Tuning

Config: /etc/redis/redis.conf

bind 127.0.0.1 10.0.1.10
protected-mode yes
maxmemory 4gb
maxmemory-policy allkeys-lru       # options: noeviction, allkeys-lfu, volatile-lru, volatile-ttl, etc.
# RDB persistence
save 900 1
save 300 10
save 60 10000
# AOF persistence (enable for durability)
appendonly yes
appendfsync everysec               # always | everysec | no
io-threads 4
requirepass YourStr0ngRedisP@ss!
rename-command FLUSHALL ""
rename-command FLUSHDB ""

RDB = fast restart, minutes of data loss. AOF = ~1s loss, slower restart. Enable both for critical data.

Sentinel (HA)

sudo apt install -y redis-sentinel

/etc/redis/sentinel.conf:

port 26379
sentinel monitor mymaster 10.0.1.10 6379 2
sentinel auth-pass mymaster YourStr0ngRedisP@ss!
sentinel down-after-milliseconds mymaster 5000
sentinel failover-timeout mymaster 60000

ACLs

ACL SETUSER appuser on >AppP@ss123 ~app:* &* +get +set +del +exists +expire -@admin
ACL SETUSER readonly on >ReadP@ss123 ~* &* +get +mget +scan -@write -@admin
ACL SAVE

Monitoring

redis-cli -a 'YourStr0ngRedisP@ss!' INFO memory     # used_memory, maxmemory
redis-cli -a 'YourStr0ngRedisP@ss!' INFO stats       # ops/sec, evicted_keys, hit ratio
redis-cli -a 'YourStr0ngRedisP@ss!' --stat           # live dashboard
redis-cli -a 'YourStr0ngRedisP@ss!' SLOWLOG GET 10   # slow commands

4. Common Patterns

Systemd Services

sudo systemctl start|stop|restart|reload postgresql   # reload for config
sudo systemctl start|stop|restart mysql
sudo systemctl start|stop|restart redis-server
journalctl -u postgresql -f   # tail logs (substitute service name)

UFW Firewall Rules

sudo ufw allow from 10.0.1.0/24 to any port 5432 proto tcp comment 'PostgreSQL'
sudo ufw allow from 10.0.1.0/24 to any port 6432 proto tcp comment 'PgBouncer'
sudo ufw allow from 10.0.1.0/24 to any port 3306 proto tcp comment 'MySQL'
sudo ufw allow from 10.0.1.0/24 to any port 6379 proto tcp comment 'Redis'

TLS/SSL

PostgreSQL: generate cert, set ssl = on + ssl_cert_file + ssl_key_file in postgresql.conf, use hostssl in pg_hba.conf.

sudo -u postgres openssl req -new -x509 -days 3650 -nodes \
  -out /etc/postgresql/16/main/server.crt -keyout /etc/postgresql/16/main/server.key -subj "/CN=db01"
sudo chmod 600 /etc/postgresql/16/main/server.key

MySQL: auto-generates certs at install. Enforce per user: ALTER USER 'appuser'@'10.0.1.%' REQUIRE SSL;

Redis: set tls-port 6380, port 0, tls-cert-file, tls-key-file, tls-ca-cert-file in redis.conf.

Health Checks

sudo -u postgres pg_isready -h 127.0.0.1 -p 5432   # exit 0 = healthy
mysqladmin -u root ping
redis-cli -a 'YourStr0ngRedisP@ss!' ping            # returns PONG

Log Rotation

PG and MySQL handle rotation internally. For Redis, add /etc/logrotate.d/redis:

/var/log/redis/*.log { weekly rotate 12 compress delaycompress missingok copytruncate }

5. Backup Strategies

PostgreSQL — Automated Backup (systemd timer)

/etc/systemd/system/pg-backup.service:

[Unit]
Description=PostgreSQL daily backup
After=postgresql.service
[Service]
Type=oneshot
User=postgres
ExecStart=/usr/local/bin/pg-backup.sh

/etc/systemd/system/pg-backup.timer:

[Unit]
Description=PG backup daily 02:00
[Timer] 02:00:00
Persistent=true
[Install]
WantedBy=timers.target

/usr/local/bin/pg-backup.sh:

#!/bin/bash
set -euo pipefail
BACKUP_DIR="/backup/postgresql"; RETENTION=14; TS=$(date +%Y%m%d_%H%M%S)
mkdir -p "$BACKUP_DIR"
for DB in $(psql -At -c "SELECT datname FROM pg_database WHERE NOT datistemplate AND datname!='postgres'"); do
  pg_dump -Fc "$DB" -f "$BACKUP_DIR/${DB}_${TS}.dump"
done
pg_dumpall --globals-only -f "$BACKUP_DIR/globals_${TS}.sql"
find "$BACKUP_DIR" -name "*.dump" -mtime +$RETENTION -delete
find "$BACKUP_DIR" -name "*.sql" -mtime +$RETENTION -delete

Enable: sudo chmod +x /usr/local/bin/pg-backup.sh && sudo systemctl daemon-reload && sudo systemctl enable --now pg-backup.timer

PostgreSQL — Point-in-Time Recovery (PITR)

Requires archive_mode = on + archive_command (see tuning above).

# Baseline: take a base backup
sudo -u postgres pg_basebackup -D /backup/postgresql/pitr_base -Ft -z -Xs -P

# Recovery: stop PG, clear data dir, restore base, create recovery.signal
sudo systemctl stop postgresql
sudo rm -rf /var/lib/postgresql/16/main/*
sudo -u postgres tar xzf /backup/postgresql/pitr_base/base.tar.gz -C /var/lib/postgresql/16/main/
sudo -u postgres tar xzf /backup/postgresql/pitr_base/pg_wal.tar.gz -C /var/lib/postgresql/16/main/pg_wal/
sudo -u postgres touch /var/lib/postgresql/16/main/recovery.signal
sudo -u postgres tee -a /var/lib/postgresql/16/main/postgresql.auto.conf <<'EOF'
restore_command = 'cp /var/lib/postgresql/16/archive/%f %p'
recovery_target_time = '2026-03-22 14:30:00'
recovery_target_action = 'promote'
EOF
sudo systemctl start postgresql

MySQL — Binary Log PITR

mysql -u root -e "FLUSH BINARY LOGS;"
sudo cp /var/log/mysql/mysql-bin.* /backup/mysql/binlogs/
# Restore: load full dump, then replay binlogs to target time
mysql -u root myapp < /backup/mysql/myapp_full.sql
mysqlbinlog --stop-datetime="2026-03-22 14:30:00" /backup/mysql/binlogs/mysql-bin.00004* | mysql -u root

MySQL — Automated Backup (systemd timer)

Same pattern as PG above. Script essentials:

#!/bin/bash
set -euo pipefail
BACKUP_DIR="/backup/mysql"; RETENTION=14; TS=$(date +%Y%m%d_%H%M%S)
mkdir -p "$BACKUP_DIR"
mysqldump -u root --all-databases --single-transaction --routines --triggers --events \
  --flush-logs --source-data=2 | gzip > "$BACKUP_DIR/all_${TS}.sql.gz"
find "$BACKUP_DIR" -name "*.sql.gz" -mtime +$RETENTION -delete

Redis — Backup

redis-cli -a 'YourStr0ngRedisP@ss!' BGSAVE
sudo cp /var/lib/redis/dump.rdb /backup/redis/dump_$(date +%Y%m%d).rdb
# AOF: sudo cp -r /var/lib/redis/appendonlydir/ /backup/redis/aof_$(date +%Y%m%d)/
# Restore: stop Redis, replace dump.rdb or AOF dir, start Redis

Anti-Patterns

Related Skills