How to Install Nix in an LXD Container

install_nix_in_an_lxd_container.md

How to Install Nix in an LXD Container

Steps to install the Nix package manager inside an Ubuntu 20.04 LXD container using the images:ubuntu/focal image:

1. On the LXD host, create an Ubuntu 20.04 container:

   lxc init images:ubuntu/focal container1
   

2. On the LXD host, enable nested security on the container:

   lxc config set container1 security.nesting true
   

3. Start the container:

   lxc start container1
   

4. Inside the container, install packages curl, gnupg2, man, rsync, and xz-utils:

   lxc exec container1 -- apt install --yes curl gnupg2 man-db rsync xz-utils
   

5. Inside the container, install Nix as user ubuntu because root may not perform a single-user Nix installation:

   lxc exec $container -- sudo --user ubuntu --login sh -c "curl --location --silent https://nixos.org/nix/install | sh"
   

install_nix_in_an_lxd_container.sh

#!/bin/sh

# Installs the Nix package manager (https://nixos.org/nix/) inside an LXD
# container.

#set -o xtrace

image=images:ubuntu/focal

if [ "$#" -eq 1 ]
then
  container=$1

  # Create a container from the given image and assign it the name from the
  # script argument.
  lxc init $image $container > /dev/null
else
  # Create a container from the given image and extract the random container
  # name that LXD assigns.
  container=`lxc init $image | grep "Instance name" | sed 's/^.* \(.*\)$/\1/'`
fi

echo "Created container $container."

# Enable nested security on the container.
# See https://github.com/NixOS/nix/issues/2649#issuecomment-518045796.
lxc config set $container security.nesting true

# Start the container.
lxc start $container

# Inside the container, install packages curl, gnupg2, man, rsync, and xz-utils.
lxc exec $container -- apt install --yes curl gnupg2 man-db rsync xz-utils

# Inside the container, install the Nix package manager as user "ubuntu".
# (see https://discuss.linuxcontainers.org/t/useful-lxc-command-aliases/2547/4)
# because root may not perform a single-user Nix installation
# (see https://github.com/NixOS/nix/issues/1559).
lxc exec $container -- sudo --user ubuntu --login sh -c "curl --location --silent https://nixos.org/nix/install | sh"

# Stop the container.
lxc stop $container

Does the installation script fail on Ubuntu 22.04 containers?

Yes, the script does fail when it attempts to install Nix:

$ lxc exec witty-koi -- sudo --user ubuntu --login sh -c "curl --location --silent https://nixos.org/nix/install | sh"
sh: you do not have 'xz' installed, which I need to unpack the binary tarball

I added package xz-utils to the list of packages that the installation script installs inside the container.

Very well.