Adopt an existing volume¶

A volume created outside syslet, by hand or by another tool, can be brought under a spec without copying its data. syslet names the podman volume after the spec, and the volume's service only creates it if it's missing, so a spec with the existing volume's name reuses it.

Find the volume's name¶

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ssh web01 sudo podman volume ls

A volume from a hand-written quadlet is usually called systemd-<unit name>; to move a whole quadlet setup over, see Migrate hand-written quadlets.

Add a locked spec with that name¶

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sysdef: volumes: "systemd-webapp-data": spec: {
    unit: {}
}

sysdef: (syslettools.#SysdefLock & {in: volumes: ["systemd-webapp-data"]}).out

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{
  "apiVersion": "v1",
  "type": "volume",
  "name": "systemd-webapp-data",
  "unit": {},
  "removalAllowed": false,
  "reclaimPolicy": "Retain"
}

Lock it from the start, so a mistake in the input can't delete data you never had in a spec before.

Leave unit empty, or match the options the volume was created with. The existing volume keeps its own options either way, and a later change to unit recreates the volume, which syslet refuses while it's locked.

Mount it and apply¶

Reference it from the container that uses the data:

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sysdef: containers: webapp: spec: {
    unit: Container: Volume: ["systemd-webapp-data.volume:/data"]
}

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"Volume": ["systemd-webapp-data.volume:/data"]

Preview and apply. The plan shows the volume as created, but that only means the unit file is new: the service finds the volume and leaves its data alone.

A name that doesn't fit your naming scheme can only change by copying the data, see Rename a volume.