uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead
https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948 this can do it nicely. Signed-off-by: Anton Arapov <anton@deadbeef.mx>
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131
nixos/doc/manual/from_md/development/unit-handling.section.xml
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nixos/doc/manual/from_md/development/unit-handling.section.xml
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<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="sec-unit-handling">
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<title>Unit handling</title>
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<para>
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To figure out what units need to be
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started/stopped/restarted/reloaded, the script first checks the
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current state of the system, similar to what
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<literal>systemctl list-units</literal> shows. For each of the
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units, the script goes through the following checks:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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Is the unit file still in the new system? If not,
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<emphasis role="strong">stop</emphasis> the service unless it
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sets <literal>X-StopOnRemoval</literal> in the
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<literal>[Unit]</literal> section to <literal>false</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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Is it a <literal>.target</literal> unit? If so,
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<emphasis role="strong">start</emphasis> it unless it sets
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<literal>RefuseManualStart</literal> in the
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<literal>[Unit]</literal> section to <literal>true</literal> or
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<literal>X-OnlyManualStart</literal> in the
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<literal>[Unit]</literal> section to <literal>true</literal>.
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Also <emphasis role="strong">stop</emphasis> the unit again
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unless it sets <literal>X-StopOnReconfiguration</literal> to
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<literal>false</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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Are the contents of the unit files different? They are compared
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by parsing them and comparing their contents. If they are
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different but only <literal>X-Reload-Triggers</literal> in the
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<literal>[Unit]</literal> section is changed,
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<emphasis role="strong">reload</emphasis> the unit. The NixOS
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module system allows setting these triggers with the option
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<link linkend="opt-systemd.services">systemd.services.<name>.reloadTriggers</link>.
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There are some additional keys in the <literal>[Unit]</literal>
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section that are ignored as well. If the unit files differ in
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any way, the following actions are performed:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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<literal>.path</literal> and <literal>.slice</literal> units
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are ignored. There is no need to restart them since changes
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in their values are applied by systemd when systemd is
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reloaded.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>.mount</literal> units are
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<emphasis role="strong">reload</emphasis>ed. These mostly
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come from the <literal>/etc/fstab</literal> parser.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>.socket</literal> units are currently ignored. This
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is to be fixed at a later point.
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</para>
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</listitem>
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<listitem>
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<para>
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The rest of the units (mostly <literal>.service</literal>
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units) are then <emphasis role="strong">reload</emphasis>ed
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if <literal>X-ReloadIfChanged</literal> in the
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<literal>[Service]</literal> section is set to
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<literal>true</literal> (exposed via
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<link linkend="opt-systemd.services">systemd.services.<name>.reloadIfChanged</link>).
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A little exception is done for units that were deactivated
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in the meantime, for example because they require a unit
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that got stopped before. These are
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<emphasis role="strong">start</emphasis>ed instead of
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reloaded.
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</para>
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</listitem>
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<listitem>
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<para>
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If the reload flag is not set, some more flags decide if the
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unit is skipped. These flags are
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<literal>X-RestartIfChanged</literal> in the
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<literal>[Service]</literal> section (exposed via
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<link linkend="opt-systemd.services">systemd.services.<name>.restartIfChanged</link>),
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<literal>RefuseManualStop</literal> in the
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<literal>[Unit]</literal> section, and
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<literal>X-OnlyManualStart</literal> in the
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<literal>[Unit]</literal> section.
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</para>
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</listitem>
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<listitem>
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<para>
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Further behavior depends on the unit having
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<literal>X-StopIfChanged</literal> in the
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<literal>[Service]</literal> section set to
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<literal>true</literal> (exposed via
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<link linkend="opt-systemd.services">systemd.services.<name>.stopIfChanged</link>).
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This is set to <literal>true</literal> by default and must
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be explicitly turned off if not wanted. If the flag is
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enabled, the unit is
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<emphasis role="strong">stop</emphasis>ped and then
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<emphasis role="strong">start</emphasis>ed. If not, the unit
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is <emphasis role="strong">restart</emphasis>ed. The goal of
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the flag is to make sure that the new unit never runs in the
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old environment which is still in place before the
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activation script is run. This behavior is different when
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the service is socket-activated, as outlined in the
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following steps.
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</para>
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</listitem>
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<listitem>
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<para>
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The last thing that is taken into account is whether the
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unit is a service and socket-activated. If
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<literal>X-StopIfChanged</literal> is
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<emphasis role="strong">not</emphasis> set, the service is
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<emphasis role="strong">restart</emphasis>ed with the
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others. If it is set, both the service and the socket are
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<emphasis role="strong">stop</emphasis>ped and the socket is
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<emphasis role="strong">start</emphasis>ed, leaving socket
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activation to start the service when it’s needed.
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</para>
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</listitem>
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</itemizedlist>
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</listitem>
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</itemizedlist>
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</section>
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