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schema.  This cannot be undone easily, so in that case you will not be

     

       
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able to go back to your original channel.</para></warning>

     

       
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</chapter>

     

···

       
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schema.  This cannot be undone easily, so in that case you will not be

     

       
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able to go back to your original channel.</para></warning>

     

       
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+
       


     

       
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+
       
<section><title>Automatic Upgrades</title>

     

       
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+
       


     

       
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+
       
<para>You can keep a NixOS system up-to-date automatically by adding

     

       
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+
       
the following to <filename>configuration.nix</filename>:

     

       
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+
       


     

       
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+
       
<programlisting>

     

       
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+
       
system.autoUpgrade.enable = true;

     

       
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+
       
</programlisting>

     

       
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+
       


     

       
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+
       
This enables a periodically executed systemd service named

     

       
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+
       
<literal>nixos-upgrade.service</literal>. It runs

     

       
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+
       
<command>nixos-rebuild switch --upgrade</command> to upgrade NixOS to

     

       
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+
       
the latest version in the current channel. (To see when the service

     

       
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+
       
runs, see <command>systemctl list-timers</command>.)  You can also

     

       
125
       
+
       
specify a channel explicitly, e.g.

     

       
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+
       


     

       
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+
       
<programlisting>

     

       
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+
       
system.autoUpgrade.channel = https://nixos.org/channels/nixos-15.09;

     

       
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+
       
</programlisting>

     

       
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+
       


     

       
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+
       
</para>

     

       
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+
       


     

       
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+
       
</section>

     

       
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+
       


     

       
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+
       


     

       
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</chapter>