With this new version, I have to sudo the command, which I never have to do with 0.1.18, is that intended?

λ skopeo -version
skopeo version 0.1.18

λ skopeo inspect docker://ubuntu:xenial # Works

λ ./result-bin/bin/skopeo -version
skopeo version 0.1.22

λ ./result-bin/bin/skopeo inspect docker://ubuntu:xenial                   
FATA[0000] open /etc/docker/certs.d/docker.io: permission denied

λ sudo ./result-bin/bin/skopeo inspect docker://ubuntu:xenial # Works

@NeQuissimus you are right.
There has to be a /etc/docker/certs.d directory that has to be readable by group docker.

because of the dependency https://github.com/projectatomic/skopeo/blob/master/vendor/github.com/containers/image/docker/docker_client.go that relies on this directory since containers/image@3aeae04

Turns out the directory /etc/docker is created at the first start of docker daemon.
But the directory /etc/docker/certs.d is not.
It seems to be a well-known docker related directory https://docs.docker.com/engine/security/certificates/.

Oooh, I see... So normally, we patch nix packages to not rely on these folders. Could we do that here, please?

@NeQuissimus i decided not to be that destructive and instead silently ignore the error caused by missing permissions.
The original code does ignore the cert dir if it is missing so i added the same logic for the permission error.

In case someone cares about maintaining its certs.d folder everything works out as expected.

@calbrecht Right, it's just that the behaviour changed between versions, that's why I preferred it being fixed.