Setup nix-on-droid

Prerequisites

• Root privilege on you android phone(it's not stable in devices without root)
• nix-on-droid installed.
• Optional: adb, pwsh You can use adb to type inputs from your computer connected with your android device. The following powershell function solves the escape problem of adb shell input text, so you don't have to escape manually.

  # Use -Enter to press enter after command input
  <#
      This script helps to input text for terminal like Termux on Android
      It may not function on input scenarios other than shell on Android
      It DOES NOT start shell on Android but simulate key press to input text.
      NOTE: if default port fails, try another port
  #>
  function Send-AdbShellInput {
      param(
          [Parameter(Mandatory)]
          [string]$InputText,
          [ushort]$Port = 5037,
          [string]$SerialNumber,
          [switch]$AcceptLine
      )
  
      begin {
          & ./Assert-AdbServer.ps1 @PSBoundParameters
  
          if (-not $SerialNumber) {
              $flags = @('-P', $Port)
          } else {
              $flags = @('-P', $Port, '-s', $SerialNumber)
          }
  
          $specials = @'
      |$%;\&~*'"`<>()
      '@
  
      }
  
      end {
          $InputText = $InputText -replace "[$([regex]::Escape($specials))]", '\$0'
          $InputText = $InputText -replace ' ', '%s'
  
          adb @flags shell input text $InputText
  
          if ($AcceptLine) {
              adb @flags shell input keyevent KEYCODE_ENTER
          }
      }
  }

  NOTE

  You can wrap the same as bash function by awk or other text manipulation tools.

Init

1. nix-on-droid may ask for url for certain file, if the url is not accessible on your phone, download it and transfer to your phone. And replace the default url as file:///sdcard/...

remember to allow file permision for nix-on-droid.

2. Type yes when nix prompt for downloads for first init.
3. Add and update channels:

   nix-channel --add https://nixos.org/channels/nixos-unstable nixpkgs && nix-channel --add https://github.com/nix-community/home-manager/archive/master.tar.gz home-manager && nix-channel --update

   TIP

   If you use the wrapper function mentioned above, would much easier to input:

   Send-AdbShellInput -InputText 'nix-channel --add https://github.com/nix-community/home-manager/archive/release-24.05.tar.gz home-manager' -AcceptLine

4. Update nix cli: default nix is out-dated, might not work with your current config like home-manager.

   nix profile install nixpkgs#nix --priority 4

Connect to nix-on-droid

• Install openssh

nix profile install nixpkgs#openssh

• create a empty ssh_config, sshd requires at least one specified. We don't specify any option in it in this guide but it's needed afterward.

mkdir -p /etc/ssh/ && touch /etc/ssh/sshd_config

• generate a host key for nix-on-droid, change the key type and passphrase as you like, they don't make too much difference.

ssh-keygen -t rsa -b 4096 -f ssh_host_rsa_key -N "" # key is generated in pwd

• create ~/.ssh/authorized_keys and paste your public key from your computer(gc ~/.ssh/<name>.pub) to this file.

mkdir -p ~/.ssh/ && touch ~/.ssh/authorized_keys && echo <pub> >> ~/.ssh/authorized_keys

TIP

Use this instead if you prefer pwsh wrapper function above, replace the pubkey name if necessary.

Send-AdbShellInput -InputText ('mkdir -p ~/.ssh/ && touch ~/.ssh/authorized_keys && echo ''{0}'' >> ~/.ssh/authorized_keys' -f (gc ~/.ssh/id_ed25519.pub)) -AcceptLine

• start ssh daemon by sshd

$(which sshd) -p 8080 -h ./ssh_host_rsa_key -d

-d is essential to know whether your port is been taken or not. See details in man sshd.

• now connect to nix-on-droid from your computer

ssh -l nix-on-droid -p <port> <ipaddr_of_phone>

NOTE

<ipaddr_of_phone> can be inspected from your Settings - About phone

Final Step

Finally you can type everything in your computer through SSH! So use nix as you like.