Manage declarative NixOS containers like imperative containers, without system rebuilds.
Each declarative container adds a full system module evaluation to every NixOS rebuild, which can be prohibitively slow for systems with many containers or when experimenting with single containers.
On the other hand, the faster imperative containers lack the full range of options of declarative containers. This tool brings you the best of both worlds.
sudo extra-container create --start <<'EOF'
{
containers.demo = {
privateNetwork = true;
hostAddress = "10.250.0.1";
localAddress = "10.250.0.2";
config = { pkgs, ... }: {
# Reduce evaluation time. Not needed for NixOS ≥ 20.03
documentation.nixos.enable = false;
networking.firewall.allowedTCPPorts = [ 50 ];
systemd.services.hello = {
wantedBy = [ "multi-user.target" ];
script = ''
while true; do
echo hello | ${pkgs.netcat}/bin/nc -lN 50
done
'';
};
};
};
}
EOF
curl 10.250.0.2:50 # Returns 'hello' from the container
# Now change the 'hello' string in the container definition to something
# else and re-run the `extra-container create --start` command.
# The updated container will be automatically restarted.
# The container is a regular container that can be controlled
# with nixos-container
nixos-container status demo
# Remove the container
sudo extra-container destroy demo{ pkgs, ... }:
let
extra-container = let
src = builtins.fetchGit {
url = "https://github.com/erikarvstedt/extra-container.git";
# Recommended: Specify a git revision hash
# rev = "...";
};
in
pkgs.callPackage src { pkgSrc = src; };
in
{
systemPackages = [ extra-container ];
}extra-container create NIXOS_CONTAINER_CONFIG_FILE
[--attr|-A attrPath]
[--nixpkgs-path|--nixos-path path]
[--start|-s | --restart-changed|-r]
[--build-args arg...]
NIXOS_CONTAINER_CONFIG_FILE is a NixOS config file with container
definitions like 'containers.mycontainer = { ... }'
--attr | -A attrPath
Select an attribute from the config expression
--nixpkgs-path
A nix expression that returns a path to the nixpkgs source
to use for building the containers
--nixos-path
Like '--nixpkgs-path', but for directly specifying the NixOS source
--start | -s
Start all created containers
Update running containers that have changed or restart them if '--restart-changed' was specified
--update-changed | -u
Update running containers with a changed system configuration by running
'switch-to-configuration' inside the container.
Restart containers with a changed container configuration
--restart-changed | -r
Restart running containers that have changed
--build-args arg...
All following args are passed to nix-build.
Must be the last option given.
Example:
extra-container create mycontainers.nix --restart-changed
extra-container create mycontainers.nix --nixpkgs-path \
'fetchTarball https://nixos.org/channels/nixos-unstable/nixexprs.tar.xz'
extra-container create mycontainers.nix --start --build-args --builders 'ssh://worker - - 8'
echo NIXOS_CONTAINER_CONFIG | extra-container create
Read the container config from stdin
Example:
extra-container create --start <<EOF
{ containers.hello = { enableTun = true; config = {}; }; }
EOF
extra-container create STORE_PATH
Create containers from STORE_PATH/etc
Examples:
Create from nixos system derivation
extra-container create /nix/store/9h..27-nixos-system-foo-18.03
Create from nixos etc derivation
extra-container create /nix/store/32..9j-etc
extra-container build ...
Build the container config and print the resulting NixOS system etc path
This command can be used like 'create', but options related
to starting are not supported
extra-container list
List all extra containers
extra-container restart CONTAINER...
Fixes the broken restart command of nixos-container (nixpkgs issue #43652)
extra-container destroy CONTAINER...
extra-container destroy --all|-a
Destroy all extra containers
extra-container CMD ARGS...
All other commands are forwarded to nixos-container
The script works like this: Take a NixOS config with container definitions and build
the system's config.system.build.etc derivation.
Because we're not building a full system we can use a reduced module set
(eval-config.nix) to improve evaluation performance.
Now link the container files from the etc derivation to the main system, like so:
nixos-system/etc/systemd/system/[email protected] -> /etc/systemd-mutable/system
nixos-system/etc/containers/CONTAINER.conf -> /etc/containers
Finally, add gcroots pointing to the linked files.
All contributions and suggestions are welcome, even if they're minor or cosmetic.
For tests run test.sh or run-tests-in-container.sh to reduce interference with your main system.
The tests add and remove temporary containers named test-* on the host system.
When changing the Usage documentation in extra-container, run ./update-readme to copy
these changes to README.md.
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