···

       
5
       
5
       
 
       
something](#ch-configuration) in that file, you should do

     

       
6
       
6
       
 
       


     

       
7
       
7
       
 
       
```ShellSession

     

       
8
       
8
       
-
       
$ nixos-rebuild switch --use-remote-sudo

     

       
8
       
8
       
+
       
# nixos-rebuild switch

     

       
9
       
9
       
 
       
```

     

       
10
       
10
       
 
       


     

       
11
       
11
       
-
       
to build the new configuration as your current user, and as the root user,

     

       
12
       
12
       
-
       
make it the default configuration for booting. `switch` will also try to

     

       
13
       
13
       
-
       
realise the configuration in the running system (e.g., by restarting system

     

       
14
       
14
       
-
       
services).

     

       
11
       
11
       
+
       
to build the new configuration, make it the default configuration for

     

       
12
       
12
       
+
       
booting, and try to realise the configuration in the running system

     

       
13
       
13
       
+
       
(e.g., by restarting system services).

     

       
15
       
14
       
 
       


     

       
16
       
15
       
 
       
::: {.warning}

     

       
17
       
16
       
 
       
This command doesn't start/stop [user services](#opt-systemd.user.services)

     
···

       
20
       
19
       
 
       
:::

     

       
21
       
20
       
 
       


     

       
22
       
21
       
 
       
::: {.warning}

     

       
23
       
23
       
-
       
Applying a configuration is an action that must be done by the root user, so the

     

       
24
       
24
       
-
       
`switch`, `boot` and `test` commands should be ran with the `--use-remote-sudo`

     

       
25
       
25
       
-
       
flag. Despite its odd name, this flag runs the activation script with elevated

     

       
26
       
26
       
-
       
permissions, regardless of whether or not the target system is remote, without

     

       
27
       
27
       
-
       
affecting the other stages of the `nixos-rebuild` call. This allows unprivileged

     

       
28
       
28
       
-
       
users to rebuild the system and only elevate their permissions when necessary.

     

       
29
       
29
       
-
       


     

       
30
       
30
       
-
       
Alternatively, one can run the whole command as root while preserving user

     

       
31
       
31
       
-
       
environment variables by prefixing the command with `sudo -E`. However, this

     

       
32
       
32
       
-
       
method may create root-owned files in `$HOME/.cache` if Nix decides to use the

     

       
33
       
33
       
-
       
cache during evaluation.

     

       
22
       
22
       
+
       
These commands must be executed as root, so you should either run them

     

       
23
       
23
       
+
       
from a root shell or by prefixing them with `sudo -i`.

     

       
34
       
24
       
 
       
:::

     

       
35
       
25
       
 
       


     

       
36
       
26
       
 
       
You can also do

     

       
37
       
27
       
 
       


     

       
38
       
28
       
 
       
```ShellSession

     

       
39
       
39
       
-
       
$ nixos-rebuild test --use-remote-sudo

     

       
29
       
29
       
+
       
# nixos-rebuild test

     

       
40
       
30
       
 
       
```

     

       
41
       
31
       
 
       


     

       
42
       
32
       
 
       
to build the configuration and switch the running system to it, but

     
···

       
47
       
37
       
 
       
There is also

     

       
48
       
38
       
 
       


     

       
49
       
39
       
 
       
```ShellSession

     

       
50
       
50
       
-
       
$ nixos-rebuild boot --use-remote-sudo

     

       
40
       
40
       
+
       
# nixos-rebuild boot

     

       
51
       
41
       
 
       
```

     

       
52
       
42
       
 
       


     

       
53
       
43
       
 
       
to build the configuration and make it the boot default, but not switch

     
···

       
57
       
47
       
 
       
GRUB 2 boot screen by giving it a different *profile name*, e.g.

     

       
58
       
48
       
 
       


     

       
59
       
49
       
 
       
```ShellSession

     

       
60
       
60
       
-
       
$ nixos-rebuild switch -p test --use-remote-sudo

     

       
50
       
50
       
+
       
# nixos-rebuild switch -p test

     

       
61
       
51
       
 
       
```

     

       
62
       
52
       
 
       


     

       
63
       
53
       
 
       
which causes the new configuration (and previous ones created using

     
···

       
68
       
58
       
 
       
A repl, or read-eval-print loop, is also available. You can inspect your configuration and use the Nix language with

     

       
69
       
59
       
 
       


     

       
70
       
60
       
 
       
```ShellSession

     

       
71
       
71
       
-
       
$ nixos-rebuild repl

     

       
61
       
61
       
+
       
# nixos-rebuild repl

     

       
72
       
62
       
 
       
```

     

       
73
       
63
       
 
       


     

       
74
       
64
       
 
       
Your configuration is loaded into the `config` variable. Use tab for autocompletion, use the `:r` command to reload the configuration files. See `:?` or [`nix repl` in the Nix manual](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-repl.html) to learn more.