commit 4e385bec15402eab76edd1c6e40a2a0638faa31a · pyrox.dev/nixpkgs

doc/builders/images.xml

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        <xi:include href="images/dockertools.section.xml" />

     

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        <xi:include href="images/ocitools.section.xml" />

     

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        <xi:include href="images/snaptools.section.xml" />

     

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        <xi:include href="images/portableservice.section.xml" />

     

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       </chapter>

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doc/builders/images/portableservice.section.md

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       # pkgs.portableService {#sec-pkgs-portableService}

     

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       `pkgs.portableService` is a function to create _portable service images_,

     

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       as read-only, immutable, `squashfs` archives.

     

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       systemd supports a concept of [Portable Services](https://systemd.io/PORTABLE_SERVICES/).

     

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       Portable Services are a delivery method for system services that uses two specific features of container management:

     

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       * Applications are bundled. I.e. multiple services, their binaries and

     

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         all their dependencies are packaged in an image, and are run directly from it.

     

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       * Stricter default security policies, i.e. sandboxing of applications.

     

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       This allows using Nix to build images which can be run on many recent Linux distributions.

     

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       The primary tool for interacting with Portable Services is `portablectl`,

     

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       and they are managed by the `systemd-portabled` system service.

     

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       :::{.note}

     

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       Portable services are supported starting with systemd 239 (released on 2018-06-22).

     

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       :::

     

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       A very simple example of using `portableService` is described below:

     

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       []{#ex-pkgs-portableService}

     

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       ```nix

     

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       pkgs.portableService {

     

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         pname = "demo";

     

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         version = "1.0";

     

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         units = [ demo-service demo-socket ];

     

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       }

     

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       ```

     

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       The above example will build an squashfs archive image in `result/$pname_$version.raw`. The image will contain the

     

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       file system structure as required by the portable service specification, and a subset of the Nix store with all the

     

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       dependencies of the two derivations in the `units` list.

     

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       `units` must be a list of derivations, and their names must be prefixed with the service name (`"demo"` in this case).

     

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       Otherwise `systemd-portabled` will ignore them.

     

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       :::{.Note}

     

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       The `.raw` file extension of the image is required by the portable services specification.

     

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       :::

     

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       Some other options available are:

     

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       - `description`, `homepage`

     

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         Are added to the `/etc/os-release` in the image and are shown by the portable services tooling.

     

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         Default to empty values, not added to os-release.

     

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       - `symlinks`

     

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         A list of attribute sets {object, symlink}. Symlinks will be created  in the root filesystem of the image to

     

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         objects in the Nix store. Defaults to an empty list.

     

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       - `contents`

     

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         A list of additional derivations to be included in the image Nix store, as-is. Defaults to an empty list.

     

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       - `squashfsTools`

     

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         Defaults to `pkgs.squashfsTools`, allows you to override the package that provides `mksquashfs`.

     

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       - `squash-compression`, `squash-block-size`

     

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         Options to `mksquashfs`. Default to `"xz -Xdict-size 100%"` and `"1M"` respectively.

     

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       A typical usage of `symlinks` would be:

     

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       ```nix

     

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         symlinks = [

     

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           { object = "${pkgs.cacert}/etc/ssl"; symlink = "/etc/ssl"; }

     

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           { object = "${pkgs.bash}/bin/bash"; symlink = "/bin/sh"; }

     

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           { object = "${pkgs.php}/bin/php"; symlink = "/usr/bin/php"; }

     

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         ];

     

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       ```

     

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       to create these symlinks for legacy applications that assume them existing globally.

     

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       Once the image is created, and deployed on a host in `/var/lib/portables/`, you can attach the image and run the service. As root run:

     

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       ```console

     

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       portablectl attach demo_1.0.raw

     

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       systemctl enable --now demo.socket

     

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       systemctl enable --now demo.service

     

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       ```

     

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       :::{.Note}

     

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       See the [man page](https://www.freedesktop.org/software/systemd/man/portablectl.html) of `portablectl` for more info on its usage.

     

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       :::