userns: skip the nobody user

[giuseppe]

improve the heuristic to detect the user namespace size needed to run an image. Hardcode the nobody user value to 65534, which is the value used by the kernel, and ignore this value when parsing /etc/passwd and /etc/group.

Closes: #1472

Signed-off-by: Giuseppe Scrivano gscrivan@redhat.com

[vrothberg]

LGTM

[Luap99]

I think we skip this check here now

[giuseppe]

I have left it just in case some image defines it to have a value different than the default 65534

[Luap99]

same here

[robbmanes]

Verified working for me in the below test..

Before:

$ podman run --name test1 --userns=auto docker.io/rapidfort/mariadb:10.10

$ podman run --name test2 --userns=auto docker.io/rapidfort/mariadb:10.10
Error: error creating container storage: could not find enough available IDs

$ podman inspect test1 | jq '.[].HostConfig.IDMappings'
{
  "UidMap": [
    "0:1:65534"
  ],
  "GidMap": [
    "0:1:65534"
  ]
}

After:

$ ./bin/podman run --name test1 --userns=auto docker.io/rapidfort/mariadb:10.10

$ ./bin/podman run --name test2 --userns=auto docker.io/rapidfort/mariadb:10.10

$ ./bin/podman inspect test1 | jq '.[].HostConfig.IDMappings'
{
  "UidMap": [
    "0:1:1024"
  ],
  "GidMap": [
    "0:1:1024"
  ]
}

$ ./bin/podman inspect test2 | jq '.[].HostConfig.IDMappings'
{
  "UidMap": [
    "0:1025:1024"
  ],
  "GidMap": [
    "0:1025:1024"
  ]

[rhatdan]

LGTM