Multistage builds do not get cached

[chocolateimage]

Issue Description

If you have a Dockerfile with multiple steps that is being used by multiple services like this:

Repository: https://gitlab.com/chocolateimage/multistage

compose.yaml

services:
  service1:
    build:
      target: service1
      dockerfile: Dockerfile

  service2:
    build:
      target: service2
      dockerfile: Dockerfile

  service3:
    build:
      target: service3
      dockerfile: Dockerfile

  service4:
    build:
      target: service4
      dockerfile: Dockerfile

And the Dockerfile:

FROM alpine:latest AS base
WORKDIR /app

FROM base AS deps
COPY dependency-generator.sh /app/
RUN [ "./dependency-generator.sh" ]

FROM base AS service-base
COPY service-runner.sh /app

# Pretend all of the services below do different things

FROM service-base AS service1
COPY --from=deps /app/deps /app/deps
ENTRYPOINT [ "./service-runner.sh", "service1" ]

FROM service-base AS service2
COPY --from=deps /app/deps /app/deps
ENTRYPOINT [ "./service-runner.sh", "service2" ]

FROM service-base AS service3
COPY --from=deps /app/deps /app/deps
ENTRYPOINT [ "./service-runner.sh", "service3" ]

FROM service-base AS service4
COPY --from=deps /app/deps /app/deps
ENTRYPOINT [ "./service-runner.sh", "service4" ]

The deps stage will be executed multiple times, this does not happen with Docker itself. In this example it will not do much, but in a real setting where you would download stuff and do CPU intensive work, this can slow down the build process by a large amount.

Steps to reproduce the issue

Steps to reproduce the issue

1. git clone https://gitlab.com/chocolateimage/multistage.git
2. podman-compose up
3. The line "Generating" your dependencies gets printed multiple times

Describe the results you received

The line "Generating" your dependencies from the deps stage gets printed multiple times.

Describe the results you expected

I expected that just like in Docker, it would get built once, and the result will be used in the individual services.

podman info output

host:
  arch: amd64
  buildahVersion: 1.40.0
  cgroupControllers:
  - cpu
  - memory
  - pids
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-1:2.1.13-1
    path: /usr/bin/conmon
    version: 'conmon version 2.1.13, commit: 82de887596ed8ee6d9b2ee85e4f167f307bb569b'
  cpuUtilization:
    idlePercent: 99.52
    systemPercent: 0.2
    userPercent: 0.28
  cpus: 4
  databaseBackend: sqlite
  distribution:
    distribution: arch
    version: unknown
  eventLogger: journald
  freeLocks: 2043
  hostname: container-test
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 6.12.31-1-lts
  linkmode: dynamic
  logDriver: journald
  memFree: 3378524160
  memTotal: 4084711424
  networkBackend: netavark
  networkBackendInfo:
    backend: netavark
    dns:
      package: aardvark-dns-1.15.0-1
      path: /usr/lib/podman/aardvark-dns
      version: aardvark-dns 1.15.0
    package: netavark-1.15.0-1
    path: /usr/lib/podman/netavark
    version: netavark 1.15.0
  ociRuntime:
    name: crun
    package: crun-1.21-1
    path: /usr/bin/crun
    version: |-
      crun version 1.21
      commit: 10269840aa07fb7e6b7e1acff6198692d8ff5c88
      rundir: /run/user/1000/crun
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  pasta:
    executable: /usr/bin/pasta
    package: passt-2025_05_12.8ec1341-1
    version: ""
  remoteSocket:
    exists: true
    path: /run/user/1000/podman/podman.sock
  rootlessNetworkCmd: pasta
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /etc/containers/seccomp.json
    selinuxEnabled: false
  serviceIsRemote: false
  slirp4netns:
    executable: ""
    package: ""
    version: ""
  swapFree: 2042097664
  swapTotal: 2042097664
  uptime: 0h 9m 45.00s
  variant: ""
plugins:
  authorization: null
  log:
  - k8s-file
  - none
  - passthrough
  - journald
  network:
  - bridge
  - macvlan
  - ipvlan
  volume:
  - local
registries: {}
store:
  configFile: /home/user/.config/containers/storage.conf
  containerStore:
    number: 4
    paused: 0
    running: 0
    stopped: 4
  graphDriverName: overlay
  graphOptions: {}
  graphRoot: /home/user/.local/share/containers/storage
  graphRootAllocated: 51462569984
  graphRootUsed: 2777255936
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Supports shifting: "false"
    Supports volatile: "true"
    Using metacopy: "false"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 26
  runRoot: /run/user/1000/containers
  transientStore: false
  volumePath: /home/user/.local/share/containers/storage/volumes
version:
  APIVersion: 5.5.0
  Built: 1747641392
  BuiltTime: Mon May 19 09:56:32 2025
  GitCommit: 0dbcb51477ee7ab8d3b47d30facf71fc38bb0c98
  GoVersion: go1.24.3
  Os: linux
  OsArch: linux/amd64
  Version: 5.5.0

Podman in a container

No

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

In a fresh libvirt/QEMU machine with Arch Linux

Additional information

I uploaded the example code on GitLab: https://gitlab.com/chocolateimage/multistage

[baude]

@flouthoc ptal