@@ -20,43 +20,107 @@ $ grep ^$(whoami): /etc/subgid

 penguin:231072:65536

 ```

-

 ### Distribution-specific hint

-#### Debian (excluding Ubuntu)

-* `sudo sh -c "echo 1 > /proc/sys/kernel/unprivileged_userns_clone"` is required

+Using Ubuntu kernel is recommended.

+

+#### Ubuntu

+* No preparation is needed.

+* `overlay2` is enabled by default ([Ubuntu-specific kernel patch](https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic.git/commit/fs/overlayfs?id=3b7da90f28fe1ed4b79ef2d994c81efbc58f1144)).

+* Known to work on Ubuntu 16.04 and 18.04.

+

+#### Debian GNU/Linux

+* Add `kernel.unprivileged_userns_clone=1` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`

+* To use `overlay2` storage driver (recommended), run `sudo modprobe overlay permit_mounts_in_userns=1` ([Debian-specific kernel patch, introduced in Debian 10](https://salsa.debian.org/kernel-team/linux/blob/283390e7feb21b47779b48e0c8eb0cc409d2c815/debian/patches/debian/overlayfs-permit-mounts-in-userns.patch)). Put the configuration to `/etc/modprobe.d` for persistence.

+* Known to work on Debian 9 and 10. `overlay2` is only supported since Debian 10 and needs `modprobe` configuration described above.

 #### Arch Linux

-* `sudo sh -c "echo 1 > /proc/sys/kernel/unprivileged_userns_clone"` is required

+* Add `kernel.unprivileged_userns_clone=1` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`

 #### openSUSE

 * `sudo modprobe ip_tables iptable_mangle iptable_nat iptable_filter` is required. (This is likely to be required on other distros as well)

+* Known to work on openSUSE 15.

+

+#### Fedora 31 and later

+* Run `sudo grubby --update-kernel=ALL --args="systemd.unified_cgroup_hierarchy=0"` and reboot.

+

+#### Fedora 30

+* No preparation is needed

+

+#### RHEL/CentOS 8

+* No preparation is needed

 #### RHEL/CentOS 7

-* `sudo sh -c "echo 28633 > /proc/sys/user/max_user_namespaces"` is required

-* [COPR package `vbatts/shadow-utils-newxidmap`](https://copr.fedorainfracloud.org/coprs/vbatts/shadow-utils-newxidmap/) needs to be installed

+* Add `user.max_user_namespaces=28633` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`

+* `systemctl --user` does not work by default. Run the daemon directly without systemd: `dockerd-rootless.sh --experimental --storage-driver vfs`

+* Known to work on RHEL/CentOS 7.7. Older releases require extra configuration steps.

+* RHEL/CentOS 7.6 and older releases require [COPR package `vbatts/shadow-utils-newxidmap`](https://copr.fedorainfracloud.org/coprs/vbatts/shadow-utils-newxidmap/) to be installed.

+* RHEL/CentOS 7.5 and older releases require running `sudo grubby --update-kernel=ALL --args="user_namespace.enable=1"` and reboot.

-## Restrictions

+## Known limitations

-* Only `vfs` graphdriver is supported. However, on [Ubuntu](http://kernel.ubuntu.com/git/ubuntu/ubuntu-artful.git/commit/fs/overlayfs?h=Ubuntu-4.13.0-25.29&id=0a414bdc3d01f3b61ed86cfe3ce8b63a9240eba7) and a few distros, `overlay2` and `overlay` are also supported.

+* Only `vfs` graphdriver is supported. However, on Ubuntu and Debian 10, `overlay2` and `overlay` are also supported.

 * Following features are not supported:

   * Cgroups (including `docker top`, which depends on the cgroups device controller)

   * Apparmor

   * Checkpoint

   * Overlay network

   * Exposing SCTP ports

-* To expose a TCP/UDP port, the host port number needs to be set to >= 1024.

+* To use `ping` command, see [Routing ping packets](#routing-ping-packets)

+* To expose privileged TCP/UDP ports (< 1024), see [Exposing privileged ports](#exposing-privileged-ports)

+

+## Install

+

+The installation script is available at https://get.docker.com/rootless .

+

+```console

+$ curl -fsSL https://get.docker.com/rootless | sh

+```

+

+Make sure to run the script as a non-root user.

+

+The script will show the environment variables that are needed to be set:

+

+```console

+$ curl -fsSL https://get.docker.com/rootless | sh

+...

+# Docker binaries are installed in /home/penguin/bin

+# WARN: dockerd is not in your current PATH or pointing to /home/penguin/bin/dockerd

+# Make sure the following environment variables are set (or add them to ~/.bashrc):

+

+export PATH=/home/penguin/bin:$PATH

+export PATH=$PATH:/sbin

+export DOCKER_HOST=unix:///run/user/1001/docker.sock

+

+#

+# To control docker service run:

+# systemctl --user (start|stop|restart) docker

+#

+```

+

+To install the binaries manually without using the installer, extract `docker-rootless-extras-<version>.tar.gz` along with `docker-<version>.tar.gz`: https://download.docker.com/linux/static/stable/x86_64/

 ## Usage

 ### Daemon

-You need to run `dockerd-rootless.sh` instead of `dockerd`.

+Use `systemctl --user` to manage the lifecycle of the daemon:

+```console

+$ systemctl --user start docker

+```

+

+To launch the daemon on system startup, enable systemd lingering:

+```console

+$ sudo loginctl enable-linger $(whoami)

+```

+To run the daemon directly without systemd, you need to run `dockerd-rootless.sh` instead of `dockerd`:

 ```console

-$ dockerd-rootless.sh --experimental

+$ dockerd-rootless.sh --experimental --storage-driver vfs

 ```

-As Rootless mode is experimental per se, currently you always need to run `dockerd-rootless.sh` with `--experimental`.

+

+As Rootless mode is experimental, currently you always need to run `dockerd-rootless.sh` with `--experimental`.

+You also need `--storage-driver vfs` unless using Ubuntu or Debian 10 kernel.

 Remarks:

 * The socket path is set to `$XDG_RUNTIME_DIR/docker.sock` by default. `$XDG_RUNTIME_DIR` is typically set to `/run/user/$UID`.

@@ -69,12 +133,24 @@ Remarks:

 ### Client

-You can just use the upstream Docker client but you need to set the socket path explicitly.

+You need to set the socket path explicitly.

 ```console

-$ docker -H unix://$XDG_RUNTIME_DIR/docker.sock run -d nginx

+$ export DOCKER_HOST=unix://$XDG_RUNTIME_DIR/docker.sock

+$ docker run -d nginx

 ```

+### Rootless Docker in Docker

+

+To run Rootless Docker inside "rootful" Docker, use `docker:<version>-dind-rootless` image instead of `docker:<version>-dind` image.

+

+```console

+$ docker run -d --name dind-rootless --privileged docker:19.03-dind-rootless --experimental

+```

+

+`docker:<version>-dind-rootless` image runs as a non-root user (UID 1000).

+However, `--privileged` is required for disabling seccomp, AppArmor, and mount masks.

+

 ### Expose Docker API socket via TCP

 To expose the Docker API socket via TCP, you need to launch `dockerd-rootless.sh` with `DOCKERD_ROOTLESS_ROOTLESSKIT_FLAGS="-p 0.0.0.0:2376:2376/tcp"`.

@@ -88,12 +164,23 @@ $ DOCKERD_ROOTLESS_ROOTLESSKIT_FLAGS="-p 0.0.0.0:2376:2376/tcp" \

 ### Routing ping packets

-To route ping packets, you need to set up `net.ipv4.ping_group_range` properly as the root.

+Add `net.ipv4.ping_group_range = 0   2147483647` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`.

+

+### Exposing privileged ports

+

+To expose privileged ports (< 1024), set `CAP_NET_BIND_SERVICE` on `rootlesskit` binary.

 ```console

-$ sudo sh -c "echo 0   2147483647  > /proc/sys/net/ipv4/ping_group_range"

+$ sudo setcap cap_net_bind_service=ep $HOME/bin/rootlesskit

 ```

+Or add `net.ipv4.ip_unprivileged_port_start=0` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`.

+

+### Limiting resources

+

+Currently rootless mode ignores cgroup-related `docker run` flags such as `--cpus` and `memory`.

+However, traditional `ulimit` and [`cpulimit`](https://github.com/opsengine/cpulimit) can be still used, though it works in process-granularity rather than container-granularity.

+

 ### Changing network stack

 `dockerd-rootless.sh` uses [slirp4netns](https://github.com/rootless-containers/slirp4netns) (if installed) or [VPNKit](https://github.com/moby/vpnkit) as the network stack by default.