script/setup/config-containerd: Use slow_chown

slow_chown is safe to add on all kernels, and when running in old
kernels (as some CI distros on purpose are), we want the expensive
fallback.

Vagrant setup and others use this script to config containerd. This
fixes userns tests with runc 1.2.0-rc.2 when running with old kernels.

Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>

script/setup/config-containerd

@@ -30,6 +30,15 @@ mkdir -p /etc/containerd
 
 cat << EOF | sudo tee /etc/containerd/config.toml
 version = 2
+
+[plugins."io.containerd.snapshotter.v1.overlayfs"]
+# slow_chown is needed to avoid an error with kernel < 5.19:
+# > "snapshotter \"overlayfs\" doesn't support idmap mounts on this host,
+# > configure \`slow_chown\` to allow a slower and expensive fallback"
+# https://github.com/containerd/containerd/pull/9920#issuecomment-1978901454
+# This is safely ignored for kernel >= 5.19.
+slow_chown = true
+
 [plugins]
   [plugins."io.containerd.grpc.v1.cri"]
     enable_selinux = ${enable_selinux}