podman system df does not honor --format and --verbose flags

Issue Description

While trying to find a reliable way to compute the disk image size for images and while I found the right approach for docker, I discovered that podman does not support the same option, making harder to keep the build script cross compatible.

To give some insights, the .Size reported by inspect commands is NOT a reliable way to get information about image size because it will report different values for the same image when some layers are shared across multiple images.

We wanted a reliable way to measure the size that does not involve using save to export the image, as that is quite time consuming.

Steps to reproduce the issue

podman system df -v --format "{{ json . }}"
Error: cannot combine --format and --verbose flags

Some command with docker works fine, producing an usable json file.

Describe the results you received

Describe the results you received-

Describe the results you expected

Be able to get a JSON file compatible with the one produced by docker command.

podman info output

host:
  arch: arm64
  buildahVersion: 1.37.3
  cgroupControllers:
  - cpu
  - io
  - memory
  - pids
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-2.1.12-2.fc40.aarch64
    path: /usr/bin/conmon
    version: 'conmon version 2.1.12, commit: '
  cpuUtilization:
    idlePercent: 99.63
    systemPercent: 0.18
    userPercent: 0.19
  cpus: 5
  databaseBackend: sqlite
  distribution:
    distribution: fedora
    variant: coreos
    version: "40"
  eventLogger: journald
  freeLocks: 2048
  hostname: localhost.localdomain
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 1000000
    uidmap:
    - container_id: 0
      host_id: 501
      size: 1
    - container_id: 1
      host_id: 100000
      size: 1000000
  kernel: 6.10.10-200.fc40.aarch64
  linkmode: dynamic
  logDriver: journald
  memFree: 1356480512
  memTotal: 4084568064
  networkBackend: netavark
  networkBackendInfo:
    backend: netavark
    dns:
      package: aardvark-dns-1.12.1-1.20240925084542154505.main.19.g56d105f.fc40.aarch64
      path: /usr/libexec/podman/aardvark-dns
      version: aardvark-dns 1.13.0-dev
    package: netavark-1.12.1-1.20240913132227547291.main.38.gcebebc7.fc40.aarch64
    path: /usr/libexec/podman/netavark
    version: netavark 1.13.0-dev
  ociRuntime:
    name: crun
    package: crun-1.17-1.20240910121144502937.main.3.g4ab4ac0.fc40.aarch64
    path: /usr/bin/crun
    version: |-
      crun version UNKNOWN
      commit: fa61d61334521bb205430e928df99f947716f88c
      rundir: /run/user/501/crun
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +LIBKRUN +WASM:wasmedge +YAJL
  os: linux
  pasta:
    executable: /usr/bin/pasta
    package: passt-0^20240906.g6b38f07-1.fc40.aarch64
    version: |
      pasta 0^20240906.g6b38f07-1.fc40.aarch64-pasta
      Copyright Red Hat
      GNU General Public License, version 2 or later
        <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
      This is free software: you are free to change and redistribute it.
      There is NO WARRANTY, to the extent permitted by law.
  remoteSocket:
    exists: true
    path: /run/user/501/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: /usr/share/containers/seccomp.json
    selinuxEnabled: true
  serviceIsRemote: true
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.2.2-2.fc40.aarch64
    version: |-
      slirp4netns version 1.2.2
      commit: 0ee2d87523e906518d34a6b423271e4826f71faf
      libslirp: 4.7.0
      SLIRP_CONFIG_VERSION_MAX: 4
      libseccomp: 2.5.5
  swapFree: 0
  swapTotal: 0
  uptime: 75h 35m 25.00s (Approximately 3.12 days)
  variant: v8
plugins:
  authorization: null
  log:
  - k8s-file
  - none
  - passthrough
  - journald
  network:
  - bridge
  - macvlan
  - ipvlan
  volume:
  - local
registries:
  search:
  - docker.io
store:
  configFile: /var/home/core/.config/containers/storage.conf
  containerStore:
    number: 0
    paused: 0
    running: 0
    stopped: 0
  graphDriverName: overlay
  graphOptions: {}
  graphRoot: /var/home/core/.local/share/containers/storage
  graphRootAllocated: 106769133568
  graphRootUsed: 13714677760
  graphStatus:
    Backing Filesystem: xfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Supports shifting: "false"
    Supports volatile: "true"
    Using metacopy: "false"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 70
  runRoot: /run/user/501/containers
  transientStore: false
  volumePath: /var/home/core/.local/share/containers/storage/volumes
version:
  APIVersion: 5.2.3
  Built: 1727136000
  BuiltTime: Tue Sep 24 01:00:00 2024
  GitCommit: ""
  GoVersion: go1.22.7
  Os: linux
  OsArch: linux/arm64
  Version: 5.2.3

Podman in a container

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

Additional information

Practical example for extracting effective image size given an image ID:

$ docker system df -v --format "{{ json .Images }}" | jq -r '.[] | select(.ID == "sha256:6c738f16d08cc1ed35ca4ceb971496ed93c1157c3254866fcdb356ee79154942") | .VirtualSize'
596.1MB

containers / podman