LXC

Docker is recommended to be used inside VM.

From documentation: https://pve.proxmox.com/wiki/Linux_Container#pct_configuration

• edit LXC container config

/etc/pve/local/lxc/contained_id.conf

features:  keyctl=1,nesting=1

• stop/start LXC container

• docker run hello-world

The vfs backend is a very simple fallback that has no copy-on-write support. Each layer is just a separate directory. Creating a new layer based on another layer is done by making a deep copy of the base layer into a new directory.
Since this backend doesn’t share diskspace use between layers, and since creating a new layer is a slow operation this is not a very practical backend. However, it still has its uses, for instance to verify other backends against, or if you need a super robust (if slow) backend that works everywhere.

docker info
...
 Server Version: 19.03.8
 Storage Driver: vfs
...

When restarted in privileged container: NOTE: restarting in privileged container do mess with user permission. Make backup/clone before.

docker info
...
 Storage Driver: aufs
  Root Dir: /var/lib/docker/aufs
  Backing Filesystem: zfs
  Dirs: 0
  Dirperm1 Supported: true
...

Solution:

cp /etc/apparmor.d/lxc/lxc-default-with-nesting /etc/apparmor.d/lxc/lxc-default-with-nesting-docker

Edit new file and update profile name and add some mount permissions:

# Do not load this file.  Rather, load /etc/apparmor.d/lxc-containers, which
# will source all profiles under /etc/apparmor.d/lxc
 
profile lxc-container-default-with-nesting-docker flags=(attach_disconnected,mediate_deleted) {
  #include <abstractions/lxc/container-base>
  #include <abstractions/lxc/start-container>
 
  deny /dev/.lxc/proc/** rw,
  deny /dev/.lxc/sys/** rw,
  mount fstype=proc -> /var/cache/lxc/**,
  mount fstype=sysfs -> /var/cache/lxc/**,
  mount options=(rw,bind),
  mount fstype=cgroup -> /sys/fs/cgroup/**,
  mount fstype=cgroup2 -> /sys/fs/cgroup/**,
  mount fstype=aufs,
  mount fstype=overlay,
}

systemctl reload apparmor

Edit /etc/pve/lxc/${container_id}.conf and append this line:

/etc/pve/lxc/${container_id}.conf

lxc.apparmor.profile: lxc-container-default-with-nesting-docker

#lxc.apparmor.profile = unconfined