Volume - Uniac

A volume is durable storage with a project-scoped identity. Its data and lifetime are independent of the service holding it.

Required and optional configuration

Volume attachment is optional and available only to singleton services, with at most one volume per service. An attachment requires:

Field	Required	Meaning
`name`	Yes	Local volume name matching `^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?$`.
`size_gb`	Yes	Number whose value, after truncation toward zero, is at least 1.
`mount_path`	Yes	Absolute path other than `/`, with no `.` or `..` segments, repeated slashes, or trailing slash.

The resulting project-scoped name is <instance>.<name>, limited to 127 characters. At deployment, the platform limits size_gb to 4096 and rejects mount paths at or below /proc, /sys, and /dev, and the path /etc/resolv.conf.

YAML composition example

In YAML composition, a volume declaration is a mapping with name, size_gb, and mount_path inside the service definition’s optional volumes list. Omitting volumes, setting it to null, or using [] declares no volume. The singleton cache service mounts cache.data at /data. Redis writes its append-only persistence files there, and the volume retains them across container replacement.

resources:
  cache-code:
    type: singleton
    image: redis:7-alpine
    start_command: redis-server --appendonly yes
    volumes:
      - name: data
        size_gb: 1
        mount_path: /data
  application:
    type: deployment
    services:
      cache:
        from: cache-code

In the generated description, the declaration is one volume object with the scoped name, size_gb, and mount_path.

Lifecycle

Declaring a new volume name provisions storage. An existing unattached volume can be attached; a volume held by another service cannot. Redeploying with the same volume name reuses its data, including when its mount path changes. Removing the volume declaration on redeploy detaches it; deleting the service also detaches its volume and preserves its data. Existing volumes cannot be resized. A volume’s state distinguishes attachment to a service from an unattached volume whose data is retained. Transitional states include provisioning, attaching, detaching, and deleting. A fresh volume contains lost+found. Deleting a volume held by a service is rejected. Explicit deletion requires name confirmation and destroys stored data.

​Required and optional configuration

​YAML composition example

​Lifecycle

Required and optional configuration

YAML composition example

Lifecycle