pyrox.dev
1# Installing from another Linux distribution {#sec-installing-from-other-distro}
2
3Because Nix (the package manager) & Nixpkgs (the Nix packages
4collection) can both be installed on any (most?) Linux distributions,
5they can be used to install NixOS in various creative ways. You can, for
6instance:
7
81. Install NixOS on another partition, from your existing Linux
9 distribution (without the use of a USB or optical device!)
10
111. Install NixOS on the same partition (in place!), from your existing
12 non-NixOS Linux distribution using `NIXOS_LUSTRATE`.
13
141. Install NixOS on your hard drive from the Live CD of any Linux
15 distribution.
16
17The first steps to all these are the same:
18
191. Install the Nix package manager:
20
21 Short version:
22
23 ```ShellSession
24 $ curl -L https://nixos.org/nix/install | sh
25 $ . $HOME/.nix-profile/etc/profile.d/nix.sh # …or open a fresh shell
26 ```
27
28 More details in the [ Nix
29 manual](https://nixos.org/nix/manual/#chap-quick-start)
30
311. Switch to the NixOS channel:
32
33 If you\'ve just installed Nix on a non-NixOS distribution, you will
34 be on the `nixpkgs` channel by default.
35
36 ```ShellSession
37 $ nix-channel --list
38 nixpkgs https://nixos.org/channels/nixpkgs-unstable
39 ```
40
41 As that channel gets released without running the NixOS tests, it
42 will be safer to use the `nixos-*` channels instead:
43
44 ```ShellSession
45 $ nix-channel --add https://nixos.org/channels/nixos-version nixpkgs
46 ```
47
48 You may want to throw in a `nix-channel --update` for good measure.
49
501. Install the NixOS installation tools:
51
52 You\'ll need `nixos-generate-config` and `nixos-install`, but this
53 also makes some man pages and `nixos-enter` available, just in case
54 you want to chroot into your NixOS partition. NixOS installs these
55 by default, but you don\'t have NixOS yet..
56
57 ```ShellSession
58 $ nix-env -f '<nixpkgs>' -iA nixos-install-tools
59 ```
60
611. ::: {.note}
62 The following 5 steps are only for installing NixOS to another
63 partition. For installing NixOS in place using `NIXOS_LUSTRATE`,
64 skip ahead.
65 :::
66
67 Prepare your target partition:
68
69 At this point it is time to prepare your target partition. Please
70 refer to the partitioning, file-system creation, and mounting steps
71 of [](#sec-installation)
72
73 If you\'re about to install NixOS in place using `NIXOS_LUSTRATE`
74 there is nothing to do for this step.
75
761. Generate your NixOS configuration:
77
78 ```ShellSession
79 $ sudo `which nixos-generate-config` --root /mnt
80 ```
81
82 You\'ll probably want to edit the configuration files. Refer to the
83 `nixos-generate-config` step in [](#sec-installation) for more
84 information.
85
86 Consider setting up the NixOS bootloader to give you the ability to
87 boot on your existing Linux partition. For instance, if you\'re
88 using GRUB and your existing distribution is running Ubuntu, you may
89 want to add something like this to your `configuration.nix`:
90
91 ```nix
92 boot.loader.grub.extraEntries = ''
93 menuentry "Ubuntu" {
94 search --set=ubuntu --fs-uuid 3cc3e652-0c1f-4800-8451-033754f68e6e
95 configfile "($ubuntu)/boot/grub/grub.cfg"
96 }
97 '';
98 ```
99
100 (You can find the appropriate UUID for your partition in
101 `/dev/disk/by-uuid`)
102
1031. Create the `nixbld` group and user on your original distribution:
104
105 ```ShellSession
106 $ sudo groupadd -g 30000 nixbld
107 $ sudo useradd -u 30000 -g nixbld -G nixbld nixbld
108 ```
109
1101. Download/build/install NixOS:
111
112 ::: {.warning}
113 Once you complete this step, you might no longer be able to boot on
114 existing systems without the help of a rescue USB drive or similar.
115 :::
116
117 ::: {.note}
118 On some distributions there are separate PATHS for programs intended
119 only for root. In order for the installation to succeed, you might
120 have to use `PATH="$PATH:/usr/sbin:/sbin"` in the following command.
121 :::
122
123 ```ShellSession
124 $ sudo PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --root /mnt
125 ```
126
127 Again, please refer to the `nixos-install` step in
128 [](#sec-installation) for more information.
129
130 That should be it for installation to another partition!
131
1321. Optionally, you may want to clean up your non-NixOS distribution:
133
134 ```ShellSession
135 $ sudo userdel nixbld
136 $ sudo groupdel nixbld
137 ```
138
139 If you do not wish to keep the Nix package manager installed either,
140 run something like `sudo rm -rv ~/.nix-* /nix` and remove the line
141 that the Nix installer added to your `~/.profile`.
142
1431. ::: {.note}
144 The following steps are only for installing NixOS in place using
145 `NIXOS_LUSTRATE`:
146 :::
147
148 Generate your NixOS configuration:
149
150 ```ShellSession
151 $ sudo `which nixos-generate-config` --root /
152 ```
153
154 Note that this will place the generated configuration files in
155 `/etc/nixos`. You\'ll probably want to edit the configuration files.
156 Refer to the `nixos-generate-config` step in
157 [](#sec-installation) for more information.
158
159 You\'ll likely want to set a root password for your first boot using
160 the configuration files because you won\'t have a chance to enter a
161 password until after you reboot. You can initalize the root password
162 to an empty one with this line: (and of course don\'t forget to set
163 one once you\'ve rebooted or to lock the account with
164 `sudo passwd -l root` if you use `sudo`)
165
166 ```nix
167 users.users.root.initialHashedPassword = "";
168 ```
169
1701. Build the NixOS closure and install it in the `system` profile:
171
172 ```ShellSession
173 $ nix-env -p /nix/var/nix/profiles/system -f '<nixpkgs/nixos>' -I nixos-config=/etc/nixos/configuration.nix -iA system
174 ```
175
1761. Change ownership of the `/nix` tree to root (since your Nix install
177 was probably single user):
178
179 ```ShellSession
180 $ sudo chown -R 0.0 /nix
181 ```
182
1831. Set up the `/etc/NIXOS` and `/etc/NIXOS_LUSTRATE` files:
184
185 `/etc/NIXOS` officializes that this is now a NixOS partition (the
186 bootup scripts require its presence).
187
188 `/etc/NIXOS_LUSTRATE` tells the NixOS bootup scripts to move
189 *everything* that\'s in the root partition to `/old-root`. This will
190 move your existing distribution out of the way in the very early
191 stages of the NixOS bootup. There are exceptions (we do need to keep
192 NixOS there after all), so the NixOS lustrate process will not
193 touch:
194
195 - The `/nix` directory
196
197 - The `/boot` directory
198
199 - Any file or directory listed in `/etc/NIXOS_LUSTRATE` (one per
200 line)
201
202 ::: {.note}
203 Support for `NIXOS_LUSTRATE` was added in NixOS 16.09. The act of
204 \"lustrating\" refers to the wiping of the existing distribution.
205 Creating `/etc/NIXOS_LUSTRATE` can also be used on NixOS to remove
206 all mutable files from your root partition (anything that\'s not in
207 `/nix` or `/boot` gets \"lustrated\" on the next boot.
208
209 lustrate /ˈlʌstreɪt/ verb.
210
211 purify by expiatory sacrifice, ceremonial washing, or some other
212 ritual action.
213 :::
214
215 Let\'s create the files:
216
217 ```ShellSession
218 $ sudo touch /etc/NIXOS
219 $ sudo touch /etc/NIXOS_LUSTRATE
220 ```
221
222 Let\'s also make sure the NixOS configuration files are kept once we
223 reboot on NixOS:
224
225 ```ShellSession
226 $ echo etc/nixos | sudo tee -a /etc/NIXOS_LUSTRATE
227 ```
228
2291. Finally, move the `/boot` directory of your current distribution out
230 of the way (the lustrate process will take care of the rest once you
231 reboot, but this one must be moved out now because NixOS needs to
232 install its own boot files:
233
234 ::: {.warning}
235 Once you complete this step, your current distribution will no
236 longer be bootable! If you didn\'t get all the NixOS configuration
237 right, especially those settings pertaining to boot loading and root
238 partition, NixOS may not be bootable either. Have a USB rescue
239 device ready in case this happens.
240 :::
241
242 ```ShellSession
243 $ sudo mv -v /boot /boot.bak &&
244 sudo /nix/var/nix/profiles/system/bin/switch-to-configuration boot
245 ```
246
247 Cross your fingers, reboot, hopefully you should get a NixOS prompt!
248
2491. If for some reason you want to revert to the old distribution,
250 you\'ll need to boot on a USB rescue disk and do something along
251 these lines:
252
253 ```ShellSession
254 # mkdir root
255 # mount /dev/sdaX root
256 # mkdir root/nixos-root
257 # mv -v root/* root/nixos-root/
258 # mv -v root/nixos-root/old-root/* root/
259 # mv -v root/boot.bak root/boot # We had renamed this by hand earlier
260 # umount root
261 # reboot
262 ```
263
264 This may work as is or you might also need to reinstall the boot
265 loader.
266
267 And of course, if you\'re happy with NixOS and no longer need the
268 old distribution:
269
270 ```ShellSession
271 sudo rm -rf /old-root
272 ```
273
2741. It\'s also worth noting that this whole process can be automated.
275 This is especially useful for Cloud VMs, where provider do not
276 provide NixOS. For instance,
277 [nixos-infect](https://github.com/elitak/nixos-infect) uses the
278 lustrate process to convert Digital Ocean droplets to NixOS from
279 other distributions automatically.