handle lxc start error: Operation not permitted Failed to mount “proc” onto “/usr/lib/x86_64-linux-gnu/lxc/rootfs/proc”

 grep /proc /proc/self/mountinfo| awk '{ print $5; }'|grep -v '/ /proc '|xargs sudo umount -l

cd /sys/fs/cgroup

umount *

for dir in net_prio net_cls cpuacct cpu; do

 test -l $dir && rm $dir

  mount -t cgroup -o $dir $dir $dir

done