[PATCH] Documentation: add ADR for VM Sources

[Alyssa Ross <alyssa.ross@unikie.com>]

Signed-off-by: Alyssa Ross <alyssa.ross@unikie.com>
---
 Documentation/decisions/009-vm-sources.adoc | 42 +++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 Documentation/decisions/009-vm-sources.adoc

diff --git a/Documentation/decisions/009-vm-sources.adoc b/Documentation/decisions/009-vm-sources.adoc
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+= 009 VM Sources
+:page-parent: Architecture Decision Records
+:page-grand_parent: About Spectrum
+
+// SPDX-FileCopyrightText: 2022 Unikie
+// SPDX-License-Identifier: GFDL-1.3-no-invariants-or-later OR CC-BY-SA-4.0
+
+== Status
+
+Proposed
+
+== Context
+
+It should be possible for Spectrum VMs to come from the root
+filesystem (for built-in VMs), or one or more
+xref:../appendices/user-partition.adoc[user partitions].  One part of
+making this work will be to have the system search multiple sources of
+VM definitions, to produce a single view of what VMs are available.
+
+== Decision
+
+The system will scan /usr/img/builtin, as well as the svc/data
+partition on each user partition, for VM definitions.  A single s6-rc
+service directory will contain generated services for VMs from all
+sources, so that tools like vm-start don't have to be aware of where
+VMs come from.  (This will continue to be distinct from the s6-rc
+database used for host system services.)  When a new source of VMs is
+discovered, an updated database will be generated and atomically
+replace the old one using
+xref:https://www.skarnet.org/software/s6-rc/s6-rc-update.html[s6-rc-update].
+
+Changes to how user partitions will be discovered and mounted, to
+support having multiple user partitions, will be determined later.
+
+== Consequences
+
+Built-in VMs can be moved into the root filesystem, allowing the
+default user partition to be empty.  This will make it easier for
+people making custom Spectrum images to add custom VMs without having
+to build Spectrum itself themselves -- they can simply replace the
+default, empty, partition with a custom one they can produce however
+they like.

base-commit: 95fba8ac6c872c2ba5e2ea8be5da9f2eb63374c8
-- 
2.35.1