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https://github.com/jeaye/nixos-in-place

Install NixOS on top of any existing Linux distribution without rebooting
https://github.com/jeaye/nixos-in-place

digitalocean install linux nixos

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Install NixOS on top of any existing Linux distribution without rebooting

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# nixos-in-place

An all-in-one script for installing NixOS on top of any existing Linux

system without using live media. When you reboot, you're in NixOS.



nixos-in-place is known to work on Ubuntu, Debian, CentOS, Fedora, Arch, and

Slackware, including x86 and x86_64 variants, with and without LVM, including

systems on [Digital

Ocean](https://github.com/jeaye/nixos-in-place#digital-ocean) droplets and

[Hetzner Cloud](https://github.com/jeaye/nixos-in-place/issues/41)!



## How to do it

0. **BACKUP**

1. See the

   [Platform-specifics](https://github.com/jeaye/nixos-in-place#platform-specifics)

   for your distribution

2. Run the following (see `./install -h` for options)



   ```bash

   $ ./install

   ```

3. **STOP AND VERIFY**, then hit `y` to confirm

4. Grab some coffee while NixOS installs

5. Hit `y` to reboot into NixOS! (root's password will be 'nixos')

6. Go through the first section of `/etc/nixos/nixos-in-place.nix` and

   remove or change it as you see fit



## What you get

A fresh install of NixOS, either minimal or graphical (your choice). Your

old system and all your old files still exist and are setup to mount on

`/old-root`. As far as the file system is concerned, NixOS is installed in

`/old-root/nixos` and `/` is rebound before spinning up the system; everything

else in `/old-root` is fair game to delete.



NixOS installs GRUB2 on top of your existing boot loader. If you'd like to boot

into `/old-root`, you can; you just need to add the GRUB entry, from

`/old-root/boot/grub`, manually in your Nix files.



## Platform-specifics

### Digital Ocean

DO makes some assumptions about static ips and networking, based on the droplet

OS and version you choose. nixos-in-place will work best from a Debian 8

droplet.



To install on a DO droplet, follow the normal steps for your platform, but add

the `-d` flag to `./install` (see `-h` for more info). Once installed, if you

clean up `/old-root`, you must keep `/old-root/etc/network` around; DO needs it!



The default configuration for NixOS disables SSH, so you'll need to use the DO

console, once you've finished the installation, in order to setup which services

you'd actually like.



I recommend installing from a tmux session, to avoid SSH timeouts and losing

access to your install part-way through. Seriously, use tmux or screen.



### Ubuntu 15.10

See [LVM](https://github.com/jeaye/nixos-in-place#lvm).

```bash

$ apt-get install -y squashfs-tools git

```



### Debian 8.2

See [LVM](https://github.com/jeaye/nixos-in-place#lvm).

```bash

$ apt-get install -y squashfs-tools git

```



### Arch

See [tmpfs](https://github.com/jeaye/nixos-in-place#tmpfs).

```bash

$ pacman -Sy wget squashfs-tools git

```



### CentOS 7

See [LVM](https://github.com/jeaye/nixos-in-place#lvm).

```bash

$ yum -y install wget squashfs-tools git

```



### Fedora 23

See [LVM](https://github.com/jeaye/nixos-in-place#lvm) and

[tmpfs](https://github.com/jeaye/nixos-in-place#tmpfs).

```bash

$ dnf -y install wget squashfs-tools git

```



### Slackware 14.1 (and -current)

Both Slackware 14.1 and -currrent have a bug where `/proc/self/mountinfo`

references a non-existent `/dev/root`. You'll need to manually create a link to

your file system root for GRUB to install properly. Example: `ln -s /dev/sda1

/dev/root`.  For the dependencies, you'll need to go through AUR; use

[sbopkg](http://blog.jeaye.com/2015/07/09/sbopkg/) or something else.

```bash

$ sbopkg squashfs-tools

```



### All platforms

It's recommended that you have 1GB of available RAM for unsquashing the NixOS

live media. If you're on a machine with less RAM, such as a VPS with 512MB, you

can quickly make a swap file for the install.



```bash

$ dd if=/dev/zero of=swap bs=1M count=1024

$ mkswap ./swap

$ chmod 600 ./swap

$ swapon ./swap

```



To remove it, after the install.



```bash

$ swapoff ./swap

$ rm -f ./swap

```



### LVM

Systems may use LVM. In which case, you'll need to specify `-g` with the proper

device for GRUB (likely `/dev/sda`). If your guessed GRUB device looks like

`/dev/mapper/xxx` and not `/dev/xxx` then you're likely using LVM.



### tmpfs

Systems may put `/tmp` onto its own tmpfs, so you may get a warning saying there

may not be enough space. Double check on your own, with `df -h`, and feel free

to continue.



## How it works

In short:



1. Install into `/nixos`

2. Wipe out boot loader with GRUB

3. Bind `/nixos` to `/`

4. Bind the old `/` to `/old-root`



More descriptively, the provided `install` script will verify your system is

sane, allow you to configure some options, and then pull down the latest ISO

from NixOS. It them enters Stage 1.



### Stage 1

Once we have the NixOS live CD ISO, we mount it locally and modify it. The

modifications enable us to imbue the image with a chroot that runs Stage 2.

Before we chroot, we bind in a number of the host's devices and files into the

chroot environment to ensure that functionality like networking will work.



### Stage 2

Once we're in the NixOS live CD chroot, we modify the NixOS configs to convey

that it's not a typical setup. After that, we install to `/nixos`, which is

bound to the host's `/nixos`. NixOS then installs GRUB and we're good to reboot

into our new machine!



## Testing

The testing suite can be run like so (requires vagrant):



```bash

$ ./test/run-all

```