Merge branch 'liw/arch' into 'main'HEADmain

docs: clarify architecture description of build VM

See merge request larswirzenius/ambient-ci!32

1 files changed, 4 insertions, 0 deletions

diff --git a/ambient.md b/ambient.md
index f9a3a36..901c423 100644
--- a/ambient.md
+++ b/ambient.md
@@ -259,12 +259,16 @@ At a very abstract level, the Ambient architecture is as follows:
   - `/dev/vdc`: the read/write artifact device: for the project to
     write a tar archive of any build artifacts it wants to export
     - this would be write-only if that was possible
+    - when the build starts, this contains only zeroes
+    - after the build a tar archive is extracted from this
   - `/dev/vdd`: the read-only dependencies device: a tar archive of
     additional dependencies in a form that the project can use
   - `/dev/vde`: the read/write cache device: a tar archive of any
     files the project wants to persist across runs; for example, for a
     Rust project, this would contains the cargo target directory
     contents
+    - when a build starts, this can be empty; the build must deal with
+      an empty cache
 * The VM additionally has a serial port where it will write the
   build log. On Linux this is `/dev/ttyS0`.
 * The VM automatically, on boot, creates