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feat(build): Configure Nixery image builder to set up env correctly

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When running Nix inside of a container image, there are several
environment-specific details that need to be configured appropriately.

Most importantly, since one of the recent Nix 2.x releases, sandboxing
during builds is enabled by default. This, however, requires kernel
privileges which commonly aren't available to containers.

Nixery's demo instance (for instance, hehe) is deployed on AppEngine
where this type of container configuration is difficult, hence this
change.

Specifically the following were changed:

* additional tools (such as tar/gzip) were introduced into the image
  because the builtins-toolset in Nix does not reference these tools
  via their store paths, which leads to them not being included
  automatically
* Nix sandboxing was disabled in the container image
* the users/groups required by Nix were added to the container setup.
  Note that these are being configured manually instead of via the
  tools from the 'shadow'-package, because the latter requires some
  user information (such as root) to be present already, which is not
  the case inside of the container
This commit is contained in:
Vincent Ambo 2019-07-24 17:46:39 +00:00
parent 18b4ae9f28
commit 948f308025
1 changed files with 27 additions and 3 deletions
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30
tools/nixery/default.nix
View file

@ -36,7 +36,7 @@ rec {
meta = {
description = "Container image build serving Nix-backed images";
homepage = "https://github.com/google/nixery";
license = lib.licenses.ascl20;
license = lib.licenses.asl20;
maintainers = [ lib.maintainers.tazjin ];
};
};
@ -69,13 +69,37 @@ rec {
# Container image containing Nixery and Nix itself. This image can
# be run on Kubernetes, published on AppEngine or whatever else is
# desired.
nixery-image = dockerTools.buildLayeredImage {
nixery-image = let
# Wrapper script for the wrapper script (meta!) which configures
# the container environment appropriately.
#
# Most importantly, sandboxing is disabled to avoid privilege
# issues in containers.
nixery-launch-script = writeShellScriptBin "nixery" ''
set -e
export NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt
mkdir /tmp
# Create the build user/group required by Nix
echo 'nixbld:x:30000:nixbld' >> /etc/group
echo 'nixbld:x:30000:30000:nixbld:/tmp:/bin/bash' >> /etc/passwd
# Disable sandboxing to avoid running into privilege issues
mkdir -p /etc/nix
echo 'sandbox = false' >> /etc/nix/nix.conf
exec ${nixery-bin}/bin/nixery
'';
in dockerTools.buildLayeredImage {
name = "nixery";
contents = [
bashInteractive
cacert
coreutils
nix
nixery-bin
nixery-launch-script
gnutar
gzip
];
};
}