Podman run error in non-root mode: "user namespaces are not enabled in /proc/sys/user/max_user_namespaces"

[Poor12]

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

/kind bug

Description

Podman run well in root-mode, however run error in non-root mode except --help.
Error is below:
cannot clone: Invalid argument
user namespaces are not enabled in /proc/sys/user/max_user_namespaces
Error: could not get runtime: cannot re-exec process

Steps to reproduce the issue:

1.switch a normal user

2.run podman

Describe the results you received:
podman run error

Describe the results you expected:
podman run well

Output of podman info --debug:
cannot clone: Invalid argument
user namespaces are not enabled in /proc/sys/user/max_user_namespaces
Error: could not get runtime: cannot re-exec process

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.):
Centos7 in Parallels Desktop. I am a newcomer to podman. Thanks for any help.

[AkihiroSuda]

CentOS 7 requires running echo “user.max_user_namespaces=10000” > /etc/sysctl.d/42-rootless.conf and sysctl --system as root

[TiloGit]

here my steps on RHEL.

[joedoe@myserver ]$ cat /proc/sys/user/max_user_namespaces
0
[joedoe@myserver ]$ sudo sysctl user.max_user_namespaces=15000
user.max_user_namespaces = 15000
[joedoe@myserver ]$ cat /proc/sys/user/max_user_namespaces
15000
[joedoe@myserver ]$ sudo usermod --add-subuids 200000-201000 --add-subgids 200000-201000 joedoe
[joedoe@myserver ]$ grep joedoe /etc/subuid /etc/subgid
/etc/subuid:joedoe:200000:1001
/etc/subgid:joedoe:200000:1001

[hjoukl]

Just for anyone stumbling upon this issue as a top search result like me: Here's some context and explanation on the previous fine answers: https://github.com/containers/podman/blob/master/docs/tutorials/rootless_tutorial.md

[Jeffy1992]

CentOS 7 requires running echo “user.max_user_namespaces=10000” > /etc/sysctl.d/42-rootless.conf and sysctl --system as root

echo '63907' > /proc/sys/user/max_user_namespaces