# Rootless mode (Experimental) The rootless mode allows running `dockerd` as an unprivileged user, using `user_namespaces(7)`, `mount_namespaces(7)`, `network_namespaces(7)`. No SETUID/SETCAP binary is required except `newuidmap` and `newgidmap`. ## Requirements * `newuidmap` and `newgidmap` need to be installed on the host. These commands are provided by the `uidmap` package on most distros. * `/etc/subuid` and `/etc/subgid` should contain >= 65536 sub-IDs. e.g. `penguin:231072:65536`. ```console $ id -u 1001 $ whoami penguin $ grep ^$(whoami): /etc/subuid penguin:231072:65536 $ grep ^$(whoami): /etc/subgid penguin:231072:65536 ``` ### Distribution-specific hint 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 * 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 * 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. ## Known limitations * 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 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 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 --storage-driver vfs ``` 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/$UID`. * The data dir is set to `~/.local/share/docker` by default. * The exec dir is set to `$XDG_RUNTIME_DIR/docker` by default. * The daemon config dir is set to `~/.config/docker` (not `~/.docker`, which is used by the client) by default. * The `dockerd-rootless.sh` script executes `dockerd` in its own user, mount, and network namespaces. You can enter the namespaces by running `nsenter -U --preserve-credentials -n -m -t $(cat $XDG_RUNTIME_DIR/docker.pid)`. * `docker info` shows `rootless` in `SecurityOptions` * `docker info` shows `none` as `Cgroup Driver` ### Client You need to set the socket path explicitly. ```console $ 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"`. ```console $ DOCKERD_ROOTLESS_ROOTLESSKIT_FLAGS="-p 0.0.0.0:2376:2376/tcp" \ dockerd-rootless.sh --experimental \ -H tcp://0.0.0.0:2376 \ --tlsverify --tlscacert=ca.pem --tlscert=cert.pem --tlskey=key.pem ``` ### Routing ping packets 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 setcap cap_net_bind_service=ep $HOME/bin/rootlesskit ``` Or add `net.ipv4.ip_unprivileged_port_start=0` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`. ### Limiting resources Currently rootless mode ignores cgroup-related `docker run` flags such as `--cpus` and `memory`. However, traditional `ulimit` and [`cpulimit`](https://github.com/opsengine/cpulimit) can be still used, though it works in process-granularity rather than container-granularity. ### Changing network stack `dockerd-rootless.sh` uses [slirp4netns](https://github.com/rootless-containers/slirp4netns) (if installed) or [VPNKit](https://github.com/moby/vpnkit) as the network stack by default. These network stacks run in userspace and might have performance overhead. See [RootlessKit documentation](https://github.com/rootless-containers/rootlesskit/tree/v0.6.0#network-drivers) for further information. Optionally, you can use `lxc-user-nic` instead for the best performance. To use `lxc-user-nic`, you need to edit [`/etc/lxc/lxc-usernet`](https://github.com/rootless-containers/rootlesskit/tree/v0.6.0#--netlxc-user-nic-experimental) and set `$DOCKERD_ROOTLESS_ROOTLESSKIT_NET=lxc-user-nic`.