51 lines
2.9 KiB
Markdown
51 lines
2.9 KiB
Markdown
# Running containerd as a non-root user
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A non-root user can execute containerd by using [`user_namespaces(7)`](http://man7.org/linux/man-pages/man7/user_namespaces.7.html).
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For example [RootlessKit](https://github.com/rootless-containers/rootlesskit) can be used for setting up a user namespace (along with mount namespace and optionally network namespace). Please refer to RootlessKit documentation for further information.
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See also [Rootless Docker documentation](https://docs.docker.com/engine/security/rootless/).
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## Daemon
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```console
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$ rootlesskit --net=slirp4netns --copy-up=/etc --copy-up=/run \
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--state-dir=/run/user/1001/rootlesskit-containerd \
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sh -c "rm -f /run/containerd; exec containerd -c config.toml"
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```
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* `--net=slirp4netns --copy-up=/etc` is only required when you want to unshare network namespaces.
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See [RootlessKit documentation](https://github.com/rootless-containers/rootlesskit/tree/v0.10.0#network-drivers) for the further information about the network drivers.
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* `--copy-up=/DIR` mounts a writable tmpfs on `/DIR` with symbolic links to the files under the `/DIR` on the parent namespace
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so that the user can add/remove files under `/DIR` in the mount namespace.
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`--copy-up=/etc` and `--copy-up=/run` are needed on typical setup.
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Depending on the containerd plugin configuration, you may also need to add more `--copy-up` options.
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* `rm -f /run/containerd` removes the "copied-up" symbolic link to `/run/containerd` on the parent namespace (if exists), which cannot be accessed by non-root users.
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The actual `/run/containerd` directory on the host is not affected.
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* `--state-dir` is set to a random directory under `/tmp` if unset. RootlessKit writes the PID to a file named `child_pid` under this directory.
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* You need to provide `config.toml` with your own path configuration. e.g.
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```toml
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version = 2
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root = "/home/penguin/.local/share/containerd"
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state = "/run/user/1001/containerd"
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[grpc]
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address = "/run/user/1001/containerd/containerd.sock"
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```
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## Client
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A client program such as `ctr` also needs to be executed inside the daemon namespaces.
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```console
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$ nsenter -U --preserve-credentials -m -n -t $(cat /run/user/1001/rootlesskit-containerd/child_pid)
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$ export CONTAINERD_ADDRESS=/run/user/1001/containerd/containerd.sock
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$ export CONTAINERD_SNAPSHOTTER=native
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$ ctr images pull docker.io/library/ubuntu:latest
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$ ctr run -t --rm --fifo-dir /tmp/foo-fifo --cgroup "" docker.io/library/ubuntu:latest foo
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```
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* `overlayfs` snapshotter does not work inside user namespaces, except on Ubuntu and Debian kernels.
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However, [`fuse-overlayfs` snapshotter](https://github.com/AkihiroSuda/containerd-fuse-overlayfs) can be used instead if running kernel >= 4.18.
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* Enabling cgroup requires cgroup v2 and systemd, e.g. `ctr run --cgroup "user.slice:foo:bar" --runc-systemd-cgroup ...` .
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See also [runc documentation](https://github.com/opencontainers/runc/blob/v1.0.0-rc92/docs/cgroup-v2.md).
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