nixpkgs/nixos/modules/system/activation/activation-script.nix
Alyssa Ross b1724b2f81 nixos/activation-script: ensure gcroots dir exists
If the Nix daemon has never been enabled (nix.enable has always been
set to false), the gcroots directory won't exist.  If the Nix daemon
is later enabled, the GC roots for booted-system and current-system
will be missing, and they might end up being garbage collected.  Since
it's cheap to add GC roots even if the daemon will never be enabled,
let's just always add them so we're okay in the case where the daemon
is enabled later.
2022-01-20 20:24:32 +00:00

273 lines
8.2 KiB
Nix

# generate the script used to activate the configuration.
{ config, lib, pkgs, ... }:
with lib;
let
addAttributeName = mapAttrs (a: v: v // {
text = ''
#### Activation script snippet ${a}:
_localstatus=0
${v.text}
if (( _localstatus > 0 )); then
printf "Activation script snippet '%s' failed (%s)\n" "${a}" "$_localstatus"
fi
'';
});
systemActivationScript = set: onlyDry: let
set' = mapAttrs (_: v: if isString v then (noDepEntry v) // { supportsDryActivation = false; } else v) set;
withHeadlines = addAttributeName set';
# When building a dry activation script, this replaces all activation scripts
# that do not support dry mode with a comment that does nothing. Filtering these
# activation scripts out so they don't get generated into the dry activation script
# does not work because when an activation script that supports dry mode depends on
# an activation script that does not, the dependency cannot be resolved and the eval
# fails.
withDrySnippets = mapAttrs (a: v: if onlyDry && !v.supportsDryActivation then v // {
text = "#### Activation script snippet ${a} does not support dry activation.";
} else v) withHeadlines;
in
''
#!${pkgs.runtimeShell}
systemConfig='@out@'
export PATH=/empty
for i in ${toString path}; do
PATH=$PATH:$i/bin:$i/sbin
done
_status=0
trap "_status=1 _localstatus=\$?" ERR
# Ensure a consistent umask.
umask 0022
${textClosureMap id (withDrySnippets) (attrNames withDrySnippets)}
'' + optionalString (!onlyDry) ''
# Make this configuration the current configuration.
# The readlink is there to ensure that when $systemConfig = /system
# (which is a symlink to the store), /run/current-system is still
# used as a garbage collection root.
ln -sfn "$(readlink -f "$systemConfig")" /run/current-system
# Prevent the current configuration from being garbage-collected.
mkdir -p /nix/var/nix/gcroots
ln -sfn /run/current-system /nix/var/nix/gcroots/current-system
exit $_status
'';
path = with pkgs; map getBin
[ coreutils
gnugrep
findutils
getent
stdenv.cc.libc # nscd in update-users-groups.pl
shadow
nettools # needed for hostname
util-linux # needed for mount and mountpoint
];
scriptType = withDry: with types;
let scriptOptions =
{ deps = mkOption
{ type = types.listOf types.str;
default = [ ];
description = "List of dependencies. The script will run after these.";
};
text = mkOption
{ type = types.lines;
description = "The content of the script.";
};
} // optionalAttrs withDry {
supportsDryActivation = mkOption
{ type = types.bool;
default = false;
description = ''
Whether this activation script supports being dry-activated.
These activation scripts will also be executed on dry-activate
activations with the environment variable
<literal>NIXOS_ACTION</literal> being set to <literal>dry-activate
</literal>. it's important that these activation scripts don't
modify anything about the system when the variable is set.
'';
};
};
in either str (submodule { options = scriptOptions; });
in
{
###### interface
options = {
system.activationScripts = mkOption {
default = {};
example = literalExpression ''
{ stdio.text =
'''
# Needed by some programs.
ln -sfn /proc/self/fd /dev/fd
ln -sfn /proc/self/fd/0 /dev/stdin
ln -sfn /proc/self/fd/1 /dev/stdout
ln -sfn /proc/self/fd/2 /dev/stderr
''';
}
'';
description = ''
A set of shell script fragments that are executed when a NixOS
system configuration is activated. Examples are updating
/etc, creating accounts, and so on. Since these are executed
every time you boot the system or run
<command>nixos-rebuild</command>, it's important that they are
idempotent and fast.
'';
type = types.attrsOf (scriptType true);
apply = set: set // {
script = systemActivationScript set false;
};
};
system.dryActivationScript = mkOption {
description = "The shell script that is to be run when dry-activating a system.";
readOnly = true;
internal = true;
default = systemActivationScript (removeAttrs config.system.activationScripts [ "script" ]) true;
defaultText = literalDocBook "generated activation script";
};
system.userActivationScripts = mkOption {
default = {};
example = literalExpression ''
{ plasmaSetup = {
text = '''
''${pkgs.libsForQt5.kservice}/bin/kbuildsycoca5"
''';
deps = [];
};
}
'';
description = ''
A set of shell script fragments that are executed by a systemd user
service when a NixOS system configuration is activated. Examples are
rebuilding the .desktop file cache for showing applications in the menu.
Since these are executed every time you run
<command>nixos-rebuild</command>, it's important that they are
idempotent and fast.
'';
type = with types; attrsOf (scriptType false);
apply = set: {
script = ''
unset PATH
for i in ${toString path}; do
PATH=$PATH:$i/bin:$i/sbin
done
_status=0
trap "_status=1 _localstatus=\$?" ERR
${
let
set' = mapAttrs (n: v: if isString v then noDepEntry v else v) set;
withHeadlines = addAttributeName set';
in textClosureMap id (withHeadlines) (attrNames withHeadlines)
}
exit $_status
'';
};
};
environment.usrbinenv = mkOption {
default = "${pkgs.coreutils}/bin/env";
defaultText = literalExpression ''"''${pkgs.coreutils}/bin/env"'';
example = literalExpression ''"''${pkgs.busybox}/bin/env"'';
type = types.nullOr types.path;
visible = false;
description = ''
The env(1) executable that is linked system-wide to
<literal>/usr/bin/env</literal>.
'';
};
};
###### implementation
config = {
system.activationScripts.stdio = ""; # obsolete
system.activationScripts.var =
''
# Various log/runtime directories.
mkdir -m 1777 -p /var/tmp
# Empty, immutable home directory of many system accounts.
mkdir -p /var/empty
# Make sure it's really empty
${pkgs.e2fsprogs}/bin/chattr -f -i /var/empty || true
find /var/empty -mindepth 1 -delete
chmod 0555 /var/empty
chown root:root /var/empty
${pkgs.e2fsprogs}/bin/chattr -f +i /var/empty || true
'';
system.activationScripts.usrbinenv = if config.environment.usrbinenv != null
then ''
mkdir -m 0755 -p /usr/bin
ln -sfn ${config.environment.usrbinenv} /usr/bin/.env.tmp
mv /usr/bin/.env.tmp /usr/bin/env # atomically replace /usr/bin/env
''
else ''
rm -f /usr/bin/env
rmdir --ignore-fail-on-non-empty /usr/bin /usr
'';
system.activationScripts.specialfs =
''
specialMount() {
local device="$1"
local mountPoint="$2"
local options="$3"
local fsType="$4"
if mountpoint -q "$mountPoint"; then
local options="remount,$options"
else
mkdir -m 0755 -p "$mountPoint"
fi
mount -t "$fsType" -o "$options" "$device" "$mountPoint"
}
source ${config.system.build.earlyMountScript}
'';
systemd.user = {
services.nixos-activation = {
description = "Run user-specific NixOS activation";
script = config.system.userActivationScripts.script;
unitConfig.ConditionUser = "!@system";
serviceConfig.Type = "oneshot";
wantedBy = [ "default.target" ];
};
};
};
}