Nix Installation Guide

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Revision as of 11:43, 4 July 2019 by imported>Symphorien (→‎NFS: use an override to install a patched nix so that the patch is picked when updating)

This guide describes various methods for installing Nix.

Single-user install

To install 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 https://nixos.org/nix/install | sh

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

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.

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.

WSL

The same caveats as NFS below apply.

NFS

Without special care, concurrent use of Nix if the nix store is on a NFS filesystem may corrupt Nix's sqlite database. To prevent this, add use-sqlite-wal = false to your nix configuration and recompile nix with this patch: 

--- a/src/libstore/sqlite.cc
+++ b/src/libstore/sqlite.cc
@@ -28,7 +28,7 @@ namespace nix {
 SQLite::SQLite(const Path & path)
 {
     if (sqlite3_open_v2(path.c_str(), &db,
-            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, 0) != SQLITE_OK)
+            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, "unix-dotfile") != SQLITE_OK)
         throw Error(format("cannot open SQLite database '%s'") % path);
 }

(source: this issue)

Nix is hard to build by hand, but you can still use vanilla nix without concurrent use, so you can install nix with a NFS store as follows:

  • Install nix with the vanilla binary installer
  • Create a file ~/.config/nixpkgs/config.nix as follows, and place the patch above alongside it.
{
        packageOverrides = pkgs: {
                nix = pkgs.nix.overrideAttrs (old: {
                                patches = (old.patches or []) ++ [ ./nfs.patch ];
                       });
        };
}
  • Run nix-env -iA nixpkgs.nix to compile and install the new, patched nix.
  • From then on, you can use nix concurrently without risk of corrupting the sqlite database.

Installing without root permissions

By using the --store parameter in nix 2.0 or PRoot, you can use Nix on systems where you have no permission to create the `/nix` directory. nix run is the preferred and faster 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 an 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 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 of an old version can be downloaded from here. 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 foo.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 on the renameat2 system call with something like "rename: unsupported operation", then you can 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 https://nixos.org/nix/install | sh

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

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.


ARMv7l

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

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