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Record the source URI of imported images at /.enroot/source #267

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Record the source URI of imported images at /.enroot/source #267

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3d3a59e
Record the source URI of imported images at /.enroot/source
alec-flowers Apr 17, 2026
6878f51
Simplify imported image provenance
alec-flowers Apr 21, 2026
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7 changes: 7 additions & 0 deletions doc/image-format.md
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Expand Up @@ -34,3 +34,10 @@ ${PWD} /mnt none x-create=dir,bind
# Example preserving the DISPLAY environment variable from the host
DISPLAY=${DISPLAY}
```

Images produced by [import](cmd/import.md) also include a provenance file at `/.enroot/source` recording the URI the image was imported from. Registry imports are recorded in enroot's canonical `docker://REGISTRY#IMAGE:TAG` form without credentials; daemon imports keep their `dockerd://` or `podman://` URI. The file is purely informational and does not affect runtime behavior; it is not updated if the image is modified and re-exported.

```sh
# Example contents
uri=docker://nvcr.io#nvidia/pytorch:25.06-py3
```
27 changes: 25 additions & 2 deletions src/docker.sh
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Expand Up @@ -303,6 +303,24 @@ docker::_parse_uri() {
printf "%s\n%s\n%s\n%s\n" "${user}" "${registry}" "${image}" "${tag}"
}

docker::_format_uri() {
local -r registry="$1" image="$2" tag="$3"

if [[ "${tag}" =~ ^sha256: ]]; then
printf "docker://%s#%s@%s\n" "${registry}" "${image}" "${tag}"
else
printf "docker://%s#%s:%s\n" "${registry}" "${image}" "${tag}"
fi
}

docker::_record_source() {
local -r rootfs="$1" uri="$2"
local -r source_meta="${rootfs}/.enroot/source"

mkdir -p "${source_meta%/*}"
printf 'uri=%s\n' "${uri}" > "${source_meta}"
}

docker::_prepare_layers() (
local -r user="$1" registry="$2" image="$3" tag="$4" arch="$5"
local layers=() config=
Expand Down Expand Up @@ -439,7 +457,7 @@ docker::digest() (
docker::import() (
local -r uri="$1"
local filename="$2" arch="$3"
local user= registry= image= tag= tmpdir= timestamp=() config= layer_count=
local user= registry= image= tag= tmpdir= timestamp=() config= layer_count= source_uri=

common::checkcmd curl grep awk jq parallel tar "${ENROOT_GZIP_PROGRAM}" find mksquashfs zstd

Expand Down Expand Up @@ -471,8 +489,10 @@ docker::import() (
common::chdir "${tmpdir}"

# Prepare layers and configure rootfs.
source_uri=$(docker::_format_uri "${registry}" "${image}" "${tag}")
docker::_prepare_layers "${user}" "${registry}" "${image}" "${tag}" "${arch}" \
| { common::read -r config; common::read -r layer_count; }
docker::_record_source "${PWD}/0" "${source_uri}"

if [ -n "${SOURCE_DATE_EPOCH-}" ]; then
timestamp=("-mkfs-time" "${SOURCE_DATE_EPOCH}" "-all-time" "${SOURCE_DATE_EPOCH}")
Expand All @@ -488,7 +508,7 @@ docker::import() (
docker::load() (
local -r uri="$1"
local name="$2" arch="$3"
local user= registry= image= tag= tmpdir= config= layer_count=
local user= registry= image= tag= tmpdir= config= layer_count= source_uri=

if [ -z "${ENROOT_NATIVE_OVERLAYFS-}" ]; then
common::err "ENROOT_NATIVE_OVERLAYFS=y is required for enroot load"
Expand Down Expand Up @@ -529,8 +549,10 @@ docker::load() (
common::chdir "${tmpdir}"

# Prepare layers and configure rootfs.
source_uri=$(docker::_format_uri "${registry}" "${image}" "${tag}")
ENROOT_SET_USER_XATTRS=y docker::_prepare_layers "${user}" "${registry}" "${image}" "${tag}" "${arch}" \
| { common::read -r config; common::read -r layer_count; }
docker::_record_source "${PWD}/0" "${source_uri}"

# Create the final filesystem by overlaying all the layers and copying to target rootfs.
common::log INFO "Loading container root filesystem..." NL
Expand Down Expand Up @@ -602,6 +624,7 @@ docker::daemon::import() (
common::fixperms rootfs
"${engine}" inspect "${image}" | common::jq '.[] | with_entries(.key|=ascii_downcase)' > config
docker::configure rootfs config "${arch}"
docker::_record_source rootfs "${uri}"

# Create the final squashfs filesystem.
common::log INFO "Creating squashfs filesystem..." NL
Expand Down