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This deprecation is part of a bigger effort to deprecate activation scripts altogether, which will take place over several releases. There are no in-tree usages of the now-deprecated reload/restart functionality.
52 lines
2.3 KiB
Markdown
52 lines
2.3 KiB
Markdown
# Activation script {#sec-activation-script}
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The activation script is a bash script called to activate the new
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configuration which resides in a NixOS system in `$out/activate`. Since its
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contents depend on your system configuration, the contents may differ.
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This chapter explains how the script works in general and some common NixOS
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snippets. Please be aware that the script is executed on every boot and system
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switch, so tasks that can be performed in other places should be performed
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there (for example letting a directory of a service be created by systemd using
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mechanisms like `StateDirectory`, `CacheDirectory`, ... or if that's not
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possible using `preStart` of the service).
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Activation scripts are defined as snippets using
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[](#opt-system.activationScripts). They can either be a simple multiline string
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or an attribute set that can depend on other snippets. The builder for the
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activation script will take these dependencies into account and order the
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snippets accordingly. As a simple example:
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```nix
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{
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system.activationScripts.my-activation-script = {
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deps = [ "etc" ];
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# supportsDryActivation = true;
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text = ''
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echo "Hallo i bims"
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'';
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};
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}
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```
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This example creates an activation script snippet that is run after the `etc`
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snippet. The special variable `supportsDryActivation` can be set so the snippet
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is also run when `nixos-rebuild dry-activate` is run. To differentiate between
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real and dry activation, the `$NIXOS_ACTION` environment variable can be
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read which is set to `dry-activate` when a dry activation is done.
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## NixOS snippets {#sec-activation-script-nixos-snippets}
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There are some snippets NixOS enables by default because disabling them would
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most likely break your system. This section lists a few of them and what they
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do:
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- `binsh` creates `/bin/sh` which points to the runtime shell
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- `etc` sets up the contents of `/etc`, this includes systemd units and
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excludes `/etc/passwd`, `/etc/group`, and `/etc/shadow` (which are managed by
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the `users` snippet)
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- `modprobe` sets the path to the `modprobe` binary for module auto-loading
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- `specialfs` is responsible for mounting filesystems like `/proc` and `sys`
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- `users` creates and removes users and groups by managing `/etc/passwd`,
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`/etc/group` and `/etc/shadow`. This also creates home directories
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- `usrbinenv` creates `/usr/bin/env`
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