136 lines
5.2 KiB
Markdown
136 lines
5.2 KiB
Markdown
# Rootless mode
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Rootless mode allows running BuildKit daemon as a non-root user.
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## Distribution-specific hint
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Using Ubuntu kernel is recommended.
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### Ubuntu
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* No preparation is needed.
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* `overlayfs` snapshotter is used by default ([Ubuntu-specific kernel patch](https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic.git/commit/fs/overlayfs?id=3b7da90f28fe1ed4b79ef2d994c81efbc58f1144)).
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### Debian GNU/Linux
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* Add `kernel.unprivileged_userns_clone=1` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`
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* `fuse-overlayfs` snapshotter is used by default.
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* To use `overlayfs` snapshotter (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.
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### Arch Linux
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* Add `kernel.unprivileged_userns_clone=1` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`
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* `fuse-overlayfs` snapshotter is used by default if running kernel >= 4.18.
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Otherwise only `native` snapshotter can be used.
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### Fedora
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* If you don't have the latest `runc` (>= v1.0.0-rc91) installed and you have `crun` instead, you need to run `buildkitd` with `--oci-worker-binary=crun`.
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* `fuse-overlayfs` snapshotter is used by default.
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### RHEL/CentOS 8
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* No preparation is needed.
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* `fuse-overlayfs` snapshotter is used by default.
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### RHEL/CentOS 7
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* Add `user.max_user_namespaces=28633` to `/etc/sysctl.conf` (or `/etc/sysctl.d`) and run `sudo sysctl -p`
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* Old releases (<= 7.6) require [extra configuration steps](https://github.com/moby/moby/pull/40076).
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* Only `native` snapshotter can be used.
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### Container-Optimized OS from Google
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* :warning: Currently unsupported. See [#879](https://github.com/moby/buildkit/issues/879).
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## Known limitations
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* `fuse-overlayfs` is used instead of `overlayfs` on most distros.
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* Network mode is always set to `network.host`.
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* No support for `containerd` worker
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## Running BuildKit in Rootless mode
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[RootlessKit](https://github.com/rootless-containers/rootlesskit/) needs to be installed.
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```console
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$ rootlesskit buildkitd
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```
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```console
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$ buildctl --addr unix:///run/user/$UID/buildkit/buildkitd.sock build ...
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```
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To isolate BuildKit daemon's network namespace from the host (recommended):
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```console
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$ rootlesskit --net=slirp4netns --copy-up=/etc --disable-host-loopback buildkitd
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```
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## Troubleshooting
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If facing an error related to `fuse-overlayfs`, try running `buildkitd` with `--oci-worker-snapshotter=native`:
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```console
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$ rootlesskit buildkitd --oci-worker-snapshotter=native
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```
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## Containerized deployment
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### Kubernetes
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See [`../examples/kubernetes`](../examples/kubernetes).
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### Docker
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```console
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$ docker run \
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--name buildkitd \
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-d \
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--security-opt seccomp=unconfined \
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--security-opt apparmor=unconfined \
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--device /dev/fuse \
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moby/buildkit:rootless --oci-worker-no-process-sandbox
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$ buildctl --addr docker-container://buildkitd build ...
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```
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If you don't mind using `--privileged` (almost safe for rootless), the `docker run` flags can be shorten as follows:
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```console
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$ docker run --name buildkitd -d --privileged moby/buildkit:rootless
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```
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#### About `--device /dev/fuse`
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Adding `--device /dev/fuse` to the `docker run` arguments is required only if you want to use `fuse-overlayfs` snapshotter.
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#### About `--oci-worker-no-process-sandbox`
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By adding `--oci-worker-no-process-sandbox` to the `buildkitd` arguments, BuildKit can be executed in a container without adding `--privileged` to `docker run` arguments.
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However, you still need to pass `--security-opt seccomp=unconfined --security-opt apparmor=unconfined` to `docker run`.
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Note that `--oci-worker-no-process-sandbox` allows build executor containers to `kill` (and potentially `ptrace` depending on the seccomp configuration) an arbitrary process in the BuildKit daemon container.
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To allow running rootless `buildkitd` without `--oci-worker-no-process-sandbox`, run `docker run` with `--security-opt systempaths=unconfined`. (For Kubernetes, set `securityContext.procMount` to `Unmasked`.)
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The `--security-opt systempaths=unconfined` flag disables the masks for the `/proc` mount in the container and potentially allows reading and writing dangerous kernel files, but it is safe when you are running `buildkitd` as non-root.
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### Change UID/GID
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The `moby/buildkit:rootless` image has the following UID/GID configuration:
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Actual ID (shown in the host and the BuildKit daemon container)| Mapped ID (shown in build executor containers)
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----------|----------
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1000 | 0
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100000 | 1
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... | ...
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165535 | 65536
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```
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$ docker exec buildkitd id
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uid=1000(user) gid=1000(user)
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$ docker exec buildkitd ps aux
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PID USER TIME COMMAND
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1 user 0:00 rootlesskit buildkitd --addr tcp://0.0.0.0:1234
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13 user 0:00 /proc/self/exe buildkitd --addr tcp://0.0.0.0:1234
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21 user 0:00 buildkitd --addr tcp://0.0.0.0:1234
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29 user 0:00 ps aux
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$ docker exec cat /etc/subuid
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user:100000:65536
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```
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To change the UID/GID configuration, you need to modify and build the BuildKit image manually.
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```
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$ vi Dockerfile
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$ make images
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$ docker run ... moby/buildkit:local-rootless ...
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```
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