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81 lines
3.2 KiB
81 lines
3.2 KiB
# 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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:::
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