Databases

The yerd db commands manage the databases inside a running SQL service. They apply to the SQL engines only - mysql, mariadb, and postgres. (Redis is a cache and has no SQL databases.) To install, start, or stop the engines themselves, see Services.

The engine must be running

Every yerd db command connects to a live server, so the target service must be installed and started first (yerd service start <svc>). Database operations need no elevation - they connect over the local socket / loopback as a passwordless local-dev superuser.

Commands

Command	Description
yerd db list <SVC>	List the databases in the service (system databases are filtered out).
yerd db create <SVC> <NAME>	Create a new database.
yerd db drop <SVC> <NAME>	Drop a database (irreversible).
yerd db backup <SVC> <NAME> <FILE>	Dump a database to a plain-SQL file.
yerd db restore <SVC> <NAME> <FILE>	Restore a database from a plain-SQL file.

yerd db create mysql my_app
yerd db list mysql
yerd db backup mysql my_app ./my_app.sql
yerd db restore mysql my_app ./my_app.sql
yerd db drop mysql my_app

Database names

create uses Yerd's portable naming policy. The daemon validates the name before building SQL. A newly created name must:

• be non-empty and at most 63 characters (the lowest limit across the engines);
• start with an ASCII letter or underscore (_);
• contain only letters, digits, and underscores.

For drop, backup, and restore, the name identifies a database that already exists. Those operations accept engine-valid names exactly as listed, including whitespace, punctuation, Unicode, quotes, backticks, periods, and leading hyphens. Only empty names and names containing NUL are rejected. SQL identifiers are quoted and escaped per engine, and backup/restore names are passed directly as one process argument without a shell.

System databases are protected

Engine-internal databases (mysql, information_schema, performance_schema, sys, postgres, template0, template1) are filtered from db list and cannot be dropped or restored over.

Backup & restore

backup runs the engine's dump tool (mysqldump, mariadb-dump, or pg_dump) and writes plain SQL. The output is streamed to a temporary file next to the destination and atomically renamed into place, so a failed dump never truncates an existing file. A relative <FILE> resolves against the current directory.

restore replays a plain-SQL file back into an existing database through the engine's interactive client (mysql, mariadb, or psql) - so the target database must already exist (yerd db create it first if needed).

# round-trip a database
yerd db create postgres shop
yerd db restore postgres shop ./shop.sql
yerd db backup postgres shop ./shop-$(date +%F).sql

See also

• Services - installing and supervising the engines
• Services & Databases guide - the full model
• yerd-services - database.rs, the pure SQL-admin boundary