Run podman on RHEL 7 with Vagrant without root

podman-rhel7-vagrant-rootless.md

More information: Basic Setup and Use of Podman in a Rootless environment

1. Enable user namespaces

   sudo sh -c 'echo "user.max_user_namespaces=15000" > /etc/sysctl.d/42-rootless.conf'
   sudo sysctl --system
   

   Fixes this error:

   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
   

   More information:

   • Enable user namespaces (on RHEL7 machines)
   • Podman run error in non-root mode: "user namespaces are not enabled in /proc/sys/user/max_user_namespaces"

2. /etc/subuid and /etc/subgid configuration

   sudo usermod --add-subuids 100000-165535 --add-subgids 100000-165535 vagrant
   

   Fixes this error:

     Error processing tar file(exit status 1): there might not be enough IDs available in the namespace (requested 0:5 for /usr/bin/write): lchown /usr/bin/write: invalid argument
   

   ⚠ If you encounter this error after podman is already installed, you'll also need to run:

   podman system migrate
   

   More information:

   • /etc/subuid and /etc/subgid configuration
   • there might not be enough IDs available in the namespace (system migrate doesn't work)

3. Install podman

   sudo yum -y install podman
   

4. Use podman, e.g.

   podman run --rm -it registry.access.redhat.com/ubi8/ubi
   

Troubleshooting

Too many open files

containers/podman#5526 (comment)