Podman: userns=keep-id creates unnamed user group

[HarryMichal]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

Container created with option --userns=keep-id gets the current user with the correct UID and GUID but the group does not have the user's name.

More info from the Toolbox realm: https://github.com/containers/toolbox/issues/523

Steps to reproduce the issue:

1. podman run --rm --userns=keep-id alpine id

Describe the results you received:

uid=1000(omichal) gid=1000

Describe the results you expected:

uid=1000(omichal) gid=1000(omichal)

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

Version:      2.1.0-dev
API Version:  1
Go Version:   go1.15rc2
Built:        Thu Jan  1 01:00:00 1970
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.16.0-dev
  cgroupVersion: v2
  conmon:
    package: conmon-2.0.21-0.3.dev.git5a6b2ac.fc33.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.21-dev, commit: 5c03a23398b94cf869f071128631ef7fd9153b3b'
  cpus: 8
  distribution:
    distribution: fedora
    version: "33"
  eventLogger: file
  hostname: harry-work
  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: 5.8.0-1.fc33.x86_64
  linkmode: dynamic
  memFree: 4838907904
  memTotal: 16656273408
  ociRuntime:
    name: crun
    package: crun-0.14.1-2.fc33.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 0.14.1
      commit: 598ea5e192ca12d4f6378217d3ab1415efeddefa
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +YAJL
  os: linux
  remoteSocket:
    exists: true
    path: /run/user/1000/podman/podman.sock
  rootless: true
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.1.4-4.dev.giteecccdb.fc33.x86_64
    version: |-
      slirp4netns version 1.1.4+dev
      commit: eecccdb96f587b11d7764556ffacfeaffe4b6e11
      libslirp: 4.3.1
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.0
  swapFree: 12363067392
  swapTotal: 12708732928
  uptime: 46h 1m 14.24s (Approximately 1.92 days)
registries:
  search:
  - registry.fedoraproject.org
  - registry.access.redhat.com
  - registry.centos.org
  - docker.io
store:
  configFile: /var/home/omichal/.config/containers/storage.conf
  containerStore:
    number: 13
    paused: 0
    running: 2
    stopped: 11
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: fuse-overlayfs-1.1.0-11.dev.git800011b.fc33.x86_64
      Version: |-
        fusermount3 version: 3.9.3
        fuse-overlayfs: version 1.1.0
        FUSE library version 3.9.3
        using FUSE kernel interface version 7.31
  graphRoot: /var/home/omichal/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 11
  runRoot: /run/user/1000/containers
  volumePath: /var/home/omichal/.local/share/containers/storage/volumes
version:
  APIVersion: 1
  Built: 0
  BuiltTime: Thu Jan  1 01:00:00 1970
  GitCommit: ""
  GoVersion: go1.15rc2
  OsArch: linux/amd64
  Version: 2.1.0-dev

Package info (e.g. output of rpm -q podman or apt list podman):

podman-2.1.0-0.169.dev.git162625f.fc33.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide?

Yes

Additional environment details (AWS, VirtualBox, physical, etc.):

Fedora Silverblue Rawhide (Rawhide.20200811.n.0)

[giuseppe]

we'd have to create and manage /etc/group as well.

Isn't /etc bind mounted from the host on toolbox?

[HarryMichal]

Hi @giuseppe!

Toolbox bind mounts /etc to /run/host/etc.

[debarshiray]

What's the way forward here?

Recently, --userns=keepid started actually creating the user, but apparently not the group.

Is it a mistake that it creates the user, or that it doesn't create the group?

[mheon]

The code to add the user is deliberate, but we did not make the code alter /etc/group as well, so we'll probably need to do that as well.

[debarshiray]

Now that Podman 2.0.5 has made it into Fedora 32, we really need to fix this. Otherwise this warning will begin to bother people every time they podman exec into a container:

/usr/bin/id: cannot find name for group ID 1000

[rhatdan]

This PR is merged.