Nix Installation Guide

From NixOS Wiki
Revision as of 05:11, 24 October 2022 by imported>V3vAP

This guide describes various more advanced methods for installing Nix.

Please take a look at https://nixos.org/download.html first for basic installation instructions and read the relevant section in the Nix manual if you want to know more about how the install process works: https://nixos.org/manual/nix/stable/#ch-installing-binary.

Single-user install

Stable Nix

To install stable Nix from any Linux distribution, use the following two commands. (Note: This assumes you have the permission to use sudo, and you are logged in as the user you want to install Nix for.) 

$ sudo install -d -m755 -o $(id -u) -g $(id -g) /nix
$ curl -L https://nixos.org/nix/install | sh

Then don't forget to reboot or run the command provided at the end of the installation script to make nix available in your system: 

$ source $HOME/.nix-profile/etc/profile.d/nix.sh

You may want to put this file directly in your ~/.bashrc or similar, so Nix would be available in any newly created shell.

When using another shell like Fish, you should ignore the previous procedure and use the Fisher plugin Nix-env.

After that being done, you can use all Nix commands as a normal user without any special permissions (for example by using sudo).

Troubleshooting

User namespaces

If the installation fails with the following error: 

installing 'nix-2.2.2'
error: cloning builder process: Invalid argument
error: unable to start build process

it is possible that user namepaces are disabled by your distribution. Since Nix 2.2, the sandbox is enabled by default on Linux which requires user namespaces. If possible enable them; the procedure depends on the distribution. In last resort, you can disable the sandbox: create the file ~/.config/nix/nix.conf and include the line sandbox = false.

Unstable Nix

To install unstable Nix with flakes support, you can use the unofficial installer by @numtide. Instructions are available in the README of the repository.

Nix store on an unusual filesystem

Case insensitive filesystem on Linux

Most Linux filesystems are case sensitive. If your nix store is on a case insensitive filesystem like CIFS on Linux, derivation outputs cannot contain two files differing only in case in the same directory. Nix can work around this by adding use-case-hack = true to your nix configuration (/etc/nix/nix.conf for a multi-user-install or ~/.config/nix/nix.conf otherwise). Unfortunately, this will change the hash of some derivations and thus make the binary cache useless.

NFS

With a Nix store residing on an NFS filesystem, concurrent use of Nix may corrupt Nix's sqlite database. To prevent this, set use-sqlite-wal = false. Since nix/pull/5475 nix/pull/5475 and it's backports to the stable branches, a patch that was previously described in this wiki is no longer needed for using Nix on WSL (Windows' Subsystem for Linux) and NFS filesystems.

Installing without root permissions

By using nix-user-chroot or PRoot, you can use Nix on systems where you have no permission to create the `/nix` directory. nix-user-chroot is the preferred option. However, it might not run on older Linux kernels, or kernels without user namespace support. With the following command, you can test whether your system supports user namespaces for unprivileged users: 

$ unshare --user --pid echo YES
YES

The output should be YES. If the command is absent, an alternative is to check the kernel compile options: 

$ zgrep CONFIG_USER_NS /proc/config.gz
CONFIG_USER_NS=y

On some systems, like Debian or Ubuntu, the kernel configuration is in a different place, so instead use: 

$ grep CONFIG_USER_NS /boot/config-$(uname -r)
CONFIG_USER_NS=y

If the output of this command is CONFIG_USER_NS=y, then your system supports user namespaces.

nix-user-chroot

nix-user-chroot is the preferred method to install use nix on systems without /nix. It also requires user namespaces to be enabled on the system. nix-user-chroot will create an environment in which you can bind mount a directory to /nix. The mountpoint will be only visible within this environment.

There are pre-build static binaries and the readme also contains the instructions to build from source (assuming rustc and cargo to be installed).

In this example, the Nix store will be installed to ~/.nix. 

$ mkdir -m 0755 ~/.nix
$ nix-user-chroot ~/.nix bash -c 'curl -L https://nixos.org/nix/install | sh'

Note that you can only use Nix and the installed programs within the shell started by nix-user-chroot: 

$ nix-user-chroot ~/.nix bash

PRoot

Obtaining PRoot

Precompiled PRoot binaries for every commit can be downloaded from here under the job artifacts. Make sure you set the executable bit of binaries you download.

Alternatively, if you have another machine with nix installed, you can build static binaries as follows:

  • create a file proot.nix:
with import <nixpkgs> {}; 
pkgsStatic.proot.override { enablePython = false; }
  • build it:
$ nix-build proot.nix

The executable is to be found in result/bin/proot.

If nix builds within proot fail with something like "no such file or directory" while the files referenced do exist, you can set PROOT_NO_SECCOMP=1 in your environment or try termux's fork of PRoot.

Installing nix

  • If you have user namespaces enabled, you should prefer using nix-user-choot to PRoot. So we can safely assume that if you got to this point in the page, you don't have user namespaces. Therefore you must disable the sandbox. Add the line
sandbox = false

to ~/.config/nix/nix.conf.

  • Create the folder where the nix store is to be located: in this example ~/.nix:
$ mkdir ~/.nix
  • Make sure PRoot is in PATH and use is to obtain a shell where /nix exists:
$ proot -b ~/.nix:/nix
  • In this new shell, Nix can be installed:
$ curl -L https://nixos.org/nix/install | sh

Note that you can only use Nix and the installed programs within the shell started by PRoot.

Troubleshooting

PRoot uses ptrace to capture and modify system calls. It happens that new system calls are created which proot does not shim yet. If you run into issues, check if:

  • you have the latest proot
  • the system calls being used are supported by proot (TODO: how to list and diff with sysnums.list?)

Since ptrace only allows one tracer to attach to a process at a time, you cant strace your process while in proot. One suggestion is to strace your application outside of proot to find what system calls are used. Alternatives may be tracing with bpftrace or trace-cmd/ftrace. (This is not elaborated on here because the author doesn't know how to do it.)

A table of system calls supported by proot-rs, which is not the same as proot, can be found at https://github.com/proot-me/proot-rs/wiki/Translation-of-system-calls .

As of PRoot 5.3.1 and 2022-Oct-24, PRoot doesn't support faccess2, which is invoked in glibc by bash through coreutils test. This makes the `[ -w /nix ]` expression fail incorrectly in the nix installer script. This can be worked around with this patch: https://github.com/proot-me/proot/pull/338 or nix-shell -I nixpkgs=channel:nixos-unstable -p '(proot.overrideAttrs (o: { patches = [ (builtins.fetchurl "https://github.com/proot-me/proot/pull/338.patch" ) ]; }))'

nix 2.0's native method

If nix is already installed on the system i.e. a self-compiled nix itself can also create a nix store in an alternative user-writable locations. The following command will create a nix store in ~/my-nix and spawn a shell, where ~/my-nix be mounted to /nix. 

$ nix run --store ~/my-nix nixpkgs.nix nixpkgs.bashInteractive

You can make all nix commands use the alternate store by specifying it in `~/.config/nix/nix.conf` as store = /home/USERNAME/my-nix.


Windows Subsystem for Linux (WSL)

As of Windows 10, Microsoft supports running Linux and Linux programs on the Windows OS. Installation instructions can be found at https://docs.microsoft.com/en-us/windows/wsl/install-win10. If you follow those instructions for using WSL2 (post-Windows 10 2004 build 19041), you can install Nix normally as described in Single-user install. You can check what version of WSL you are using by running wsl --list --verbose from the Windows command line.

WSL1 (pre-Windows 10 2004 build 19041)

Running Nix is much simpler on WSL2, so we recommend that if at all possible. If WSL2 is not available, then Nix can be installed and run from WSL1 with a few workarounds.

If you perform no workarounds, you will see that busybox doesn't work in Nix due to WSL1 not handling 32-bit binaries. This can be remedied by following the solution laid out in nixpkgs issue#24954:

  • Install and configure QEMU and binfmt-support
$ sudo apt install qemu-user-static
$ sudo update-binfmts --install i386 /usr/bin/qemu-i386-static --magic '\x7fELF\x01\x01\x01\x03\x00\x00\x00\x00\x00\x00\x00\x00\x03\x00\x03\x00\x01\x00\x00\x00' --mask '\xff\xff\xff\xff\xff\xff\xff\xfc\xff\xff\xff\xff\xff\xff\xff\xff\xf8\xff\xff\xff\xff\xff\xff\xff'
  • Start the binfmt-support service every WSL1 login:
$ sudo service binfmt-support start

ARMv7l

Because there is no officially produced ARMv7l installer, this page describes how to build your own: Nix_on_ARM.

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