--no-hosts option prevents adding custom entries to containers /etc/hosts

[ykuksenko]

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

/kind bug

Description

In #11835 it was mentioned that the --no-hosts option will prevent entries from the hosts /etc/hosts file from being included. However when using the option it is now also impossible to use the --add-host argument.

In my use case I need to both have a clean starting point for the container /etc/hosts file and also be able to add custom entries in the container ideally without having to modify the base image.

Steps to reproduce the issue:

podman run --rm -ti --no-hosts --add-host blah:2.2.2.2 fedora cat /etc/hosts

Describe the results you received:

Error: --no-hosts and --add-host cannot be set together

Describe the results you expected:

2.2.2.2 blah
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

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

Output of podman version:

podman version 4.1.0

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.26.1
  cgroupControllers:
  - cpuset
  - cpu
  - io
  - memory
  - hugetlb
  - pids
  - misc
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon-2.1.0-2.fc36.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.1.0, commit: '
  cpuUtilization:
    idlePercent: 89.29
    systemPercent: 4.45
    userPercent: 6.26
  cpus: 2
  distribution:
    distribution: fedora
    variant: cloud
    version: "36"
  eventLogger: journald
  hostname: container
  idMappings:
    gidmap: null
    uidmap: null
  kernel: 5.17.6-300.fc36.x86_64
  linkmode: dynamic
  logDriver: journald
  memFree: 1023909888
  memTotal: 12177186816
  networkBackend: cni
  ociRuntime:
    name: crun
    package: crun-1.4.4-1.fc36.x86_64
    path: /usr/bin/crun
    version: |-
      crun version 1.4.4
      commit: 6521fcc5806f20f6187eb933f9f45130c86da230
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    path: /run/podman/podman.sock
  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: false
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: true
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns-1.2.0-0.2.beta.0.fc36.x86_64
    version: |-
      slirp4netns version 1.2.0-beta.0
      commit: 477db14a24ff1a3de3a705e51ca2c4c1fe3dda64
      libslirp: 4.6.1
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.5.3
  swapFree: 8586784768
  swapTotal: 8589930496
  uptime: 48m 1.41s
plugins:
  log:
  - k8s-file
  - none
  - passthrough
  - journald
  network:
  - bridge
  - macvlan
  - ipvlan
  volume:
  - local
registries:
  search:
  - docker.io
store:
  configFile: /etc/containers/storage.conf
  containerStore:
    number: 28
    paused: 0
    running: 26
    stopped: 2
  graphDriverName: overlay
  graphOptions:
    overlay.mountopt: nodev,metacopy=on
  graphRoot: /var/lib/containers/storage
  graphRootAllocated: 42313187328
  graphRootUsed: 33317249024
  graphStatus:
    Backing Filesystem: btrfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "true"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 104
  runRoot: /run/containers/storage
  volumePath: /var/lib/containers/storage/volumes
version:
  APIVersion: 4.1.0
  Built: 1651853754
  BuiltTime: Fri May  6 16:15:54 2022
  GitCommit: ""
  GoVersion: go1.18
  Os: linux
  OsArch: linux/amd64
  Version: 4.1.0

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

podman-4.1.0-1.fc36.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/main/troubleshooting.md)
Yes

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

[ykuksenko]

Actually I can just mount my own /etc/hosts file so this is not really required.
I will leave open in case you think differently but otherwise feel free to close as is.

[Luap99]

This is the correct behaviour, I know it is not very good but I don't think we should break it.

I added a new containers.conf option in v4.1 for this base_hosts_file="none" https://github.com/containers/common/blob/main/docs/containers.conf.5.md#containers-table
I think this is what you want. You could also set it to a custom path when you always want specific entries.