"sudo: unable to resolve host" when running sudo in pod

[matpen]

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

/kind bug

Description

When running sudo in a container within a pod, a warning similar to the following is emitted on console:

sudo: unable to resolve host a0b3a5d3b2a7

This does not happen when running the same image outside of a pod, and seems to be related to the /etc/hosts file (see below).

Steps to reproduce the issue:

1. Build an image derived from ubuntu:16.04 (let this image be myimage, introduce a system user (e.g. myuser) and install sudo (apt-get -yq install sudo);

2. Run a dummy command via sudo using the image outside any pod, and notice that the command succeeds without warning: podman run --rm localhost/myimage:latest sudo -u myuser true

3. Repeat the test after adding --pod new:test_pod to the command line, thereby running the image inside a pod, and notice that a warning is output: podman run --pod new:test_pod --rm localhost/myimage:latest sudo -u myuser true

Describe the results you received:

The warning sudo: unable to resolve host a0b3a5d3b2a7 is printed. Apart from that, the command seems to succeed, but I am unsure about other implications.

Describe the results you expected:

No warning should be printed.

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

This seems to be due to the /etc/hosts file, see below. Without pod:

matt@matt-laptop:~$ podman run --rm localhost/myimage:latest cat /etc/hosts
127.0.0.1	localhost
127.0.1.1	mat-laptop # NOTICE THIS

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.88.3.105	5d616f9a3ab4 # NOTICE THIS

With pod:

matt@matt-laptop:~$ podman run --pod test_pod --rm localhost/myimage:latest cat /etc/hosts
127.0.0.1	localhost
127.0.1.1	matt-laptop # NOTICE THIS

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.88.3.104	mrsdalloway # NOTICE THIS

After a quick research, the following issues might be related: #1745, #2504, #3405

Output of podman version:

Version:            1.4.2
RemoteAPI Version:  1
Go Version:         go1.12
Git Commit:         9b6a98cfd7813513e5697888baa93318395a2055
Built:              Fri Jun 28 22:48:29 2019
OS/Arch:            linux/amd64

Output of podman info --debug:

debug:
  compiler: gc
  git commit: 9b6a98cfd7813513e5697888baa93318395a2055
  go version: go1.12
  podman version: 1.4.2
host:
  BuildahVersion: 1.9.0
  Conmon:
    package: Unknown
    path: /usr/local/libexec/crio/conmon
    version: 'conmon version 0.3.0, commit: 8455ce1ef385120deb827d0f0588c04357bad4c4'
  Distribution:
    distribution: ubuntu
    version: "16.04"
  MemFree: 10103779328
  MemTotal: 16684048384
  OCIRuntime:
    package: 'runc: /usr/sbin/runc'
    path: /usr/sbin/runc
    version: 'runc version spec: 1.0.1-dev'
  SwapFree: 17036734464
  SwapTotal: 17036734464
  arch: amd64
  cpus: 8
  hostname: matt-laptop
  kernel: 4.4.0-154-generic
  os: linux
  rootless: false
  uptime: 37m 21.7s
registries:
  blocked: null
  insecure: null
  search: null
store:
  ConfigFile: /etc/containers/storage.conf
  ContainerStore:
    number: 18
  GraphDriverName: overlay
  GraphOptions: null
  GraphRoot: /home/matt/data/podman/root
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 109
  RunRoot: /var/run/containers/storage
  VolumePath: /home/matt/data/podman/root/volumes

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

Physical host (laptop):

matt@matt-laptop:~$ uname -a
Linux matt-laptop 4.4.0-154-generic #181-Ubuntu SMP Tue Jun 25 05:29:03 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
matt@matt-laptop:~$ lsb_release -d
Description:	Ubuntu 16.04.6 LTS

[mheon]

Interesting... We should be sharing UTS and network namespaces, so they should share hostname and /etc/hosts across all containers in the pod.

Is your pod, by chance, named mrsdalloway (I'm assuming that's how we sourced the pod's hostname).

[matpen]

Is your pod, by chance, named mrsdalloway (I'm assuming that's how we sourced the pod's hostname)

Nope, no idea where the name comes from: seems like randomly generated to me. However, I just tested and if I use a different pod, the IP changes, but the name is the same.

matt@matt-laptop:~$ podman run --pod new:test_pod2 --rm localhost/myimage:latest cat /etc/hosts
127.0.0.1	localhost
127.0.1.1	matt-laptop

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
10.88.3.106	mrsdalloway

[rhatdan]

I think we need to raise this to a much higher priority.

[mheon]

@baude We should discuss this one at bug scrub tomorrow, get it assigned

[haircommander]

/assign
seems to be related to #3732 and a couple of other things