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91 lines
3.7 KiB
Markdown
91 lines
3.7 KiB
Markdown
# Rootless mode (Experimental)
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The rootless mode allows running `dockerd` as an unprivileged user, using `user_namespaces(7)`, `mount_namespaces(7)`, `network_namespaces(7)`.
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No SETUID/SETCAP binary is required except `newuidmap` and `newgidmap`.
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## Requirements
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* `newuidmap` and `newgidmap` need to be installed on the host. These commands are provided by the `uidmap` package on most distros.
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* `/etc/subuid` and `/etc/subgid` should contain >= 65536 sub-IDs. e.g. `penguin:231072:65536`.
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```console
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$ id -u
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1001
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$ whoami
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penguin
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$ grep ^$(whoami): /etc/subuid
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penguin:231072:65536
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$ grep ^$(whoami): /etc/subgid
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penguin:231072:65536
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```
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### Distribution-specific hint
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#### Debian (excluding Ubuntu)
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* `sudo sh -c "echo 1 > /proc/sys/kernel/unprivileged_userns_clone"` is required
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#### Arch Linux
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* `sudo sh -c "echo 1 > /proc/sys/kernel/unprivileged_userns_clone"` is required
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#### openSUSE
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* `sudo modprobe ip_tables iptable_mangle iptable_nat iptable_filter` is required. (This is likely to be required on other distros as well)
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#### RHEL/CentOS 7
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* `sudo sh -c "echo 28633 > /proc/sys/user/max_user_namespaces"` is required
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* [COPR package `vbatts/shadow-utils-newxidmap`](https://copr.fedorainfracloud.org/coprs/vbatts/shadow-utils-newxidmap/) needs to be installed
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## Restrictions
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* 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.
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* Following features are not supported:
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* Cgroups (including `docker top`, which depends on the cgroups device controller)
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* Apparmor
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* Checkpoint
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* Overlay network
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* Exposing SCTP ports
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* To expose a TCP/UDP port, the host port number needs to be set to >= 1024.
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## Usage
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### Daemon
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You need to run `dockerd-rootless.sh` instead of `dockerd`.
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```console
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$ dockerd-rootless.sh --experimental
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```
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As Rootless mode is experimental per se, currently you always need to run `dockerd-rootless.sh` with `--experimental`.
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Remarks:
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* The socket path is set to `$XDG_RUNTIME_DIR/docker.sock` by default. `$XDG_RUNTIME_DIR` is typically set to `/run/user/$UID`.
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* The data dir is set to `~/.local/share/docker` by default.
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* The exec dir is set to `$XDG_RUNTIME_DIR/docker` by default.
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* The daemon config dir is set to `~/.config/docker` (not `~/.docker`, which is used by the client) by default.
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* 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 $XDG_RUNTIME_DIR/docker.pid)`.
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### Client
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You can just use the upstream Docker client but you need to set the socket path explicitly.
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```console
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$ docker -H unix://$XDG_RUNTIME_DIR/docker.sock run -d nginx
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```
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### Routing ping packets
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To route ping packets, you need to set up `net.ipv4.ping_group_range` properly as the root.
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```console
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$ sudo sh -c "echo 0 2147483647 > /proc/sys/net/ipv4/ping_group_range"
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```
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### Changing network stack
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`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.
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These network stacks run in userspace and might have performance overhead. See [RootlessKit documentation](https://github.com/rootless-containers/rootlesskit/tree/v0.4.0#network-drivers) for further information.
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Optionally, you can use `lxc-user-nic` instead for the best performance.
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To use `lxc-user-nic`, you need to edit [`/etc/lxc/lxc-usernet`](https://github.com/rootless-containers/rootlesskit/tree/v0.4.0#--netlxc-user-nic-experimental) and set `$DOCKERD_ROOTLESS_ROOTLESSKIT_NET=lxc-user-nic`.
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