Minimal bootable disk image builder
feat(uniboot,space): add OCI source resolution and GPT disk images
Add Uniboot.Source module for resolving components (kernel, init) from
local files, directories, or OCI registries with XDG caching. Refactor
space build to use uniboot for GPT disk images instead of raw disk.
Update pid1 init to try /dev/vda1 (GPT partition) before /dev/vda.
+142
-1
+3
dune-project
+3
dune-project
+13
-1
lib/dune
+13
-1
lib/dune
+112
lib/source.ml
+112
lib/source.ml
···
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(*---------------------------------------------------------------------------
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Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
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SPDX-License-Identifier: ISC
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---------------------------------------------------------------------------*)
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(** Resolve component images from local files or OCI registries.
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All components (kernel, init, userspace services) follow the same pattern:
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specify a local file path or an OCI image reference. OCI images are fetched
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and cached in the XDG cache directory. This mirrors LinuxKit's model where
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every component is an OCI image. *)
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let is_file fs path =
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match Eio.Path.kind ~follow:false Eio.Path.(fs / path) with
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| `Regular_file -> true
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| _ -> false
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| exception Eio.Io _ -> false
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let is_dir fs path =
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match Eio.Path.kind ~follow:false Eio.Path.(fs / path) with
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| `Directory -> true
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| _ -> false
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| exception Eio.Io _ -> false
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let rec find_in fs ~names dir =
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let entries =
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try Eio.Path.read_dir Eio.Path.(fs / dir) with Eio.Io _ -> []
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in
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let found =
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List.find_opt
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(fun name -> List.mem name names && is_file fs (Filename.concat dir name))
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entries
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in
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match found with
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| Some name -> Some (Filename.concat dir name)
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| None ->
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let subdirs =
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List.filter_map
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(fun entry ->
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let path = Filename.concat dir entry in
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if is_dir fs path then Some path else None)
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entries
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in
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List.find_map (find_in fs ~names) subdirs
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let xdge env =
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let fs = Eio.Stdenv.fs env in
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Xdge.create fs "uniboot"
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let oci_cache xdge =
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let cache_dir = Eio.Path.(Xdge.cache_dir xdge / "oci") in
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let cache = Oci.Cache.v cache_dir in
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Oci.Cache.init cache;
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cache
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let checkout_dir xdge =
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let path = Eio.Path.native_exn (Xdge.cache_dir xdge) in
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Filename.concat path "checkout"
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let oci_fetch ~env ~cache ?platform image =
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let net = Eio.Stdenv.net env in
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let clock = Eio.Stdenv.clock env in
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let domain_mgr = Eio.Stdenv.domain_mgr env in
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let client = Oci.Fetch.create_client ~net ~clock in
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Fmt.pr "Fetching %a...@." Oci.Image.pp image;
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Oci.fetch ~show_progress:true ?platform ~cache ~client ~domain_mgr image
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let oci_checkout ~env ~cache ~checkout_dir image =
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let fs = Eio.Stdenv.fs env in
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Eio.Path.mkdirs ~exists_ok:true ~perm:0o755 Eio.Path.(fs / checkout_dir);
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let root = Eio.Path.(fs / checkout_dir) in
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Oci.checkout ~cache ~root image
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let resolve ~env ~names ?platform spec =
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let fs = Eio.Stdenv.fs env in
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(* 1. Local file *)
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if is_file fs spec then spec
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(* 2. Local directory — search for named files in it *)
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else if is_dir fs spec then
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match find_in fs ~names spec with
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| Some path -> path
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| None ->
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failwith
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(Fmt.str "no matching file in %s (searched: %s)" spec
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(String.concat ", " names))
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else
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(* 3. OCI reference — check XDG cache, then fetch *)
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match Oci.Image.of_string spec with
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| Error (`Msg msg) ->
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failwith
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(Fmt.str "not found: %s (not a valid OCI reference: %s)" spec msg)
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| Ok image -> (
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let xdge = xdge env in
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let checkout = checkout_dir xdge in
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let image_dir = Filename.concat checkout (Oci.Image.to_string image) in
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match find_in fs ~names image_dir with
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| Some path ->
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Fmt.pr " %s (cached)@." path;
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path
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| None -> (
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let cache = oci_cache xdge in
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oci_fetch ~env ~cache ?platform image;
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oci_checkout ~env ~cache ~checkout_dir:checkout image;
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match find_in fs ~names image_dir with
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| Some path ->
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Fmt.pr " %s@." path;
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path
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| None ->
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failwith
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(Fmt.str
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"no matching file found in OCI image %a (searched: %s)"
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Oci.Image.pp image (String.concat ", " names))))
+2
lib/uniboot.ml
+2
lib/uniboot.ml
+9
lib/uniboot.mli
+9
lib/uniboot.mli
···
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val guid_linux_swap : Uuidm.t
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(** Linux swap partition type GUID. *)
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(** {1 OCI Image Resolution}
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Resolve component specifications to local file paths. Accepts local file
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paths (used as-is) or OCI image references (fetched from a registry and
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extracted). Follows LinuxKit's model where every component is an OCI image.
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*)
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module Source = Source