I have a Centos 7.6 default kernel with lxc 3.0.3, I try to create snapshot clone an unprivileged container, but the start of the cloned container failed with an overlay error message “- Operation not permited - Failed to mount …”.
I tried the kernel-lt 4.4 form elrepo with a more recent “overlay” module I have the same problem.
Is it possible to create a snapshot clone of an unprivileged container ? I have no problem with privileged container.
I’ve not used that feature in a long time, but I suspect it’s making use of unprivileged overlayfs which is currently only in the Ubuntu kernel. It’s been brought up upstream a couple of times but so far hasn’t been included.
It’s on @sforshee’s list to do another push at getting that change upstream.
That’s a patch which was written for Ubuntu a while back and has been kept updated by the Ubuntu kernel team. Some distributions may have picked it up on their own but it is not part of the mainline kernel at this time.
I seem to remember @brauner pointing me to the RedHat security advisory for this which I assume means that a kernel update is now available with the fix.