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Introduce dockerTools.buildNixShellImage

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Silvan Mosberger 2022-05-09 20:43:52 +02:00
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139
doc/builders/images/dockertools.section.md
View file

@ -394,3 +394,142 @@ buildImage {
};
}
```
## buildNixShellImage {#ssec-pkgs-dockerTools-buildNixShellImage}
Create a Docker image that sets up an environment similar to that of running `nix-shell` on a derivation.
When run in Docker, this environment somewhat resembles the Nix sandbox typically used by `nix-build`, with a major difference being that access to the internet is allowed.
It additionally also behaves like an interactive `nix-shell`, running things like `shellHook` and setting an interactive prompt.
If the derivation is fully buildable (i.e. `nix-build` can be used on it), running `buildDerivation` inside such a Docker image will build the derivation, with all its outputs being available in the correct `/nix/store` paths, pointed to by the respective environment variables like `$out`, etc.
::: {.warning}
The behavior doesn't match `nix-shell` or `nix-build` exactly and this function is known not to work correctly for e.g. fixed-output derivations, content-addressed derivations, impure derivations and other special types of derivations.
:::
### Arguments
`drv`
: The derivation on which to base the Docker image.
Adding packages to the Docker image is possible by e.g. extending the list of `nativeBuildInputs` of this derivation like
```nix
buildNixShellImage {
drv = someDrv.overrideAttrs (old: {
nativeBuildInputs = old.nativeBuildInputs or [] ++ [
somethingExtra
];
});
# ...
}
```
Similarly, you can extend the image initialization script by extending `shellHook`
`name` _optional_
: The name of the resulting image.
*Default:* `drv.name + "-env"`
`tag` _optional_
: Tag of the generated image.
*Default:* the resulting image derivation output path's hash
`uid`/`gid` _optional_
: The user/group ID to run the container as. This is like a `nixbld` build user.
*Default:* 1000/1000
`homeDirectory` _optional_
: The home directory of the user the container is running as
*Default:* `/build`
`shell` _optional_
: The path to the `bash` binary to use as the shell. This shell is started when running the image.
*Default:* `pkgs.bashInteractive + "/bin/bash"`
`command` _optional_
: Run this command in the environment of the derivation, in an interactive shell. See the `--command` option in the [`nix-shell` documentation](https://nixos.org/manual/nix/stable/command-ref/nix-shell.html?highlight=nix-shell#options).
*Default:* (none)
`run` _optional_
: Same as `command`, but runs the command in a non-interactive shell instead. See the `--run` option in the [`nix-shell` documentation](https://nixos.org/manual/nix/stable/command-ref/nix-shell.html?highlight=nix-shell#options).
*Default:* (none)
### Example
The following shows how to build the `pkgs.hello` package inside a Docker container built with `buildNixShellImage`.
```nix
with import <nixpkgs> {};
dockerTools.buildNixShellImage {
drv = hello;
}
```
Build the derivation:
```console
nix-build hello.nix
```
these 8 derivations will be built:
/nix/store/xmw3a5ln29rdalavcxk1w3m4zb2n7kk6-nix-shell-rc.drv
...
Creating layer 56 from paths: ['/nix/store/crpnj8ssz0va2q0p5ibv9i6k6n52gcya-stdenv-linux']
Creating layer 57 with customisation...
Adding manifests...
Done.
/nix/store/cpyn1lc897ghx0rhr2xy49jvyn52bazv-hello-2.12-env.tar.gz
Load the image:
```console
docker load -i result
```
0d9f4c4cd109: Loading layer [==================================================>] 2.56MB/2.56MB
...
ab1d897c0697: Loading layer [==================================================>] 10.24kB/10.24kB
Loaded image: hello-2.12-env:pgj9h98nal555415faa43vsydg161bdz
Run the container:
```console
docker run -it hello-2.12-env:pgj9h98nal555415faa43vsydg161bdz
```
[nix-shell:/build]$
In the running container, run the build:
```console
buildDerivation
```
unpacking sources
unpacking source archive /nix/store/8nqv6kshb3vs5q5bs2k600xpj5bkavkc-hello-2.12.tar.gz
...
patching script interpreter paths in /nix/store/z5wwy5nagzy15gag42vv61c2agdpz2f2-hello-2.12
checking for references to /build/ in /nix/store/z5wwy5nagzy15gag42vv61c2agdpz2f2-hello-2.12...
Check the build result:
```console
$out/bin/hello
```
Hello, world!

183
pkgs/build-support/docker/default.nix
View file

@ -19,6 +19,7 @@
, pigz
, rsync
, runCommand
, runCommandNoCC
, runtimeShell
, shadow
, skopeo
@ -30,6 +31,7 @@
, vmTools
, writeReferencesToFile
, writeScript
, writeShellScriptBin
, writeText
, writeTextDir
, writePython3
@ -1027,4 +1029,185 @@ rec {
'';
in
result;
# This function streams a docker image that behaves like a nix-shell for a derivation
streamNixShellImage =
{ # The derivation whose environment this docker image should be based on
drv
, # Image Name
name ? drv.name + "-env"
, # Image tag, the Nix's output hash will be used if null
tag ? null
, # User id to run the container as. Defaults to 1000, because many
# binaries don't like to be run as root
uid ? 1000
, # Group id to run the container as, see also uid
gid ? 1000
, # The home directory of the user
homeDirectory ? "/build"
, # The path to the bash binary to use as the shell. See `NIX_BUILD_SHELL` in `man nix-shell`
shell ? bashInteractive + "/bin/bash"
, # Run this command in the environment of the derivation, in an interactive shell. See `--command` in `man nix-shell`
command ? null
, # Same as `command`, but runs the command in a non-interactive shell instead. See `--run` in `man nix-shell`
run ? null
}:
assert lib.assertMsg (! (drv.drvAttrs.__structuredAttrs or false))
"streamNixShellImage: Does not work with the derivation ${drv.name} because it uses __structuredAttrs";
assert lib.assertMsg (command == null || run == null)
"streamNixShellImage: Can't specify both command and run";
let
# A binary that calls the command to build the derivation
builder = writeShellScriptBin "buildDerivation" ''
exec ${lib.escapeShellArg (stringValue drv.drvAttrs.builder)} ${lib.escapeShellArgs (map stringValue drv.drvAttrs.args)}
'';
staticPath = "${dirOf shell}:${lib.makeBinPath [ builder ]}";
# https://github.com/NixOS/nix/blob/2.8.0/src/nix-build/nix-build.cc#L493-L526
rcfile = writeText "nix-shell-rc" ''
unset PATH
dontAddDisableDepTrack=1
# TODO: https://github.com/NixOS/nix/blob/2.8.0/src/nix-build/nix-build.cc#L506
[ -e $stdenv/setup ] && source $stdenv/setup
PATH=${staticPath}:"$PATH"
SHELL=${lib.escapeShellArg shell}
BASH=${lib.escapeShellArg shell}
set +e
[ -n "$PS1" -a -z "$NIX_SHELL_PRESERVE_PROMPT" ] && PS1='\n\[\033[1;32m\][nix-shell:\w]\$\[\033[0m\] '
if [ "$(type -t runHook)" = function ]; then
runHook shellHook
fi
unset NIX_ENFORCE_PURITY
shopt -u nullglob
shopt -s execfail
${optionalString (command != null || run != null) ''
${optionalString (command != null) command}
${optionalString (run != null) run}
exit
''}
'';
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/globals.hh#L464-L465
sandboxBuildDir = "/build";
# This function closely mirrors what this Nix code does:
# https://github.com/NixOS/nix/blob/2.8.0/src/libexpr/primops.cc#L1102
# https://github.com/NixOS/nix/blob/2.8.0/src/libexpr/eval.cc#L1981-L2036
stringValue = value:
# We can't just use `toString` on all derivation attributes because that
# would not put path literals in the closure. So we explicitly copy
# those into the store here
if builtins.typeOf value == "path" then "${value}"
else if builtins.typeOf value == "list" then toString (map stringValue value)
else toString value;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L992-L1004
drvEnv = lib.mapAttrs' (name: value:
let str = stringValue value;
in if lib.elem name (drv.drvAttrs.passAsFile or [])
then lib.nameValuePair "${name}Path" (writeText "pass-as-text-${name}" str)
else lib.nameValuePair name str
) drv.drvAttrs //
# A mapping from output name to the nix store path where they should end up
# https://github.com/NixOS/nix/blob/2.8.0/src/libexpr/primops.cc#L1253
lib.genAttrs drv.outputs (output: builtins.unsafeDiscardStringContext drv.${output}.outPath);
# Environment variables set in the image
envVars = {
# Root certificates for internet access
SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1027-L1030
# PATH = "/path-not-set";
# Allows calling bash and `buildDerivation` as the Cmd
PATH = staticPath;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1032-L1038
HOME = homeDirectory;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1040-L1044
NIX_STORE = storeDir;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1046-L1047
# TODO: Make configurable?
NIX_BUILD_CORES = "1";
} // drvEnv // {
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1008-L1010
NIX_BUILD_TOP = sandboxBuildDir;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1012-L1013
TMPDIR = sandboxBuildDir;
TEMPDIR = sandboxBuildDir;
TMP = sandboxBuildDir;
TEMP = sandboxBuildDir;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1015-L1019
PWD = sandboxBuildDir;
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1071-L1074
# We don't set it here because the output here isn't handled in any special way
# NIX_LOG_FD = "2";
# https://github.com/NixOS/nix/blob/2.8.0/src/libstore/build/local-derivation-goal.cc#L1076-L1077
TERM = "xterm-256color";
};
in streamLayeredImage {
inherit name tag;
contents = [
binSh
usrBinEnv
(fakeNss.override {
# Allows programs to look up the build user's home directory
# https://github.com/NixOS/nix/blob/ffe155abd36366a870482625543f9bf924a58281/src/libstore/build/local-derivation-goal.cc#L906-L910
# Slightly differs however: We use the passed-in homeDirectory instead of sandboxBuildDir.
# We're doing this because it's arguably a bug in Nix that sandboxBuildDir is used here: https://github.com/NixOS/nix/issues/6379
extraPasswdLines = [
"nixbld:x:${toString uid}:${toString gid}:Build user:${homeDirectory}:/noshell"
];
extraGroupLines = [
"nixbld:!:${toString gid}:"
];
})
];
fakeRootCommands = ''
# Allows any user to create new directories in the Nix store (for the build result)
mkdir -p .${storeDir}
chmod a+w+t .${storeDir}
# Gives the user control over the build directory
mkdir -p .${sandboxBuildDir}
chown -R ${toString uid}:${toString gid} .${sandboxBuildDir}
'';
# Run this image as the given uid/gid
config.User = "${toString uid}:${toString gid}";
config.Cmd =
# https://github.com/NixOS/nix/blob/2.8.0/src/nix-build/nix-build.cc#L185-L186
# https://github.com/NixOS/nix/blob/2.8.0/src/nix-build/nix-build.cc#L534-L536
if run == null
then [ shell "--rcfile" rcfile ]
else [ shell rcfile ];
config.WorkingDir = sandboxBuildDir;
config.Env = lib.mapAttrsToList (name: value: "${name}=${value}") envVars;
};
# Wrapper around streamNixShellImage to build an image from the result
buildNixShellImage = { drv, ... }@args:
let
stream = streamNixShellImage args;
in
runCommand "${drv.name}-env.tar.gz"
{
inherit (stream) imageName;
passthru = { inherit (stream) imageTag; };
nativeBuildInputs = [ pigz ];
} "${stream} | pigz -nT > $out";
}