Start an unprivileged container failed

hi, I create an unprivileged container in ubuntu18, it can be created successfully, but start failed, can anyone help where I am wrong?

  1. mkdir -p ~/.config/lxc

  2. cp /etc/lxc/default.conf ~/.config/lxc/default.conf

  3. vi ~/.config/lxc/default.conf

  4. added lxc.idmap = u 0 165536 65536
    lxc.idmap = g 0 165536 65536

  5. lxc-create -t download -n mylxc – --no-valiate

  6. choose the distribute such as: Debian stretch amd64

  7. lxc-start -n mylxc -d
    lxc-start: my: lxccontainer.c: wait_on_daemonized_start: 842 Received container state “ABORTING” instead of “RUNNING”
    lxc-start: my: tools/lxc_start.c: main: 330 The container failed to start

What steps I missed? thanks.