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nixpkgs/nixos/modules/virtualisation/containers.nix

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{ config, lib, pkgs, ... }:
with lib;
let
# The container's init script, a small wrapper around the regular
# NixOS stage-2 init script.
containerInit = (cfg:
let
renderExtraVeth = (name: cfg:
''
echo "Bringing ${name} up"
ip link set dev ${name} up
${optionalString (cfg.localAddress != null) ''
echo "Setting ip for ${name}"
ip addr add ${cfg.localAddress} dev ${name}
''}
${optionalString (cfg.localAddress6 != null) ''
echo "Setting ip6 for ${name}"
ip -6 addr add ${cfg.localAddress6} dev ${name}
''}
${optionalString (cfg.hostAddress != null) ''
echo "Setting route to host for ${name}"
ip route add ${cfg.hostAddress} dev ${name}
''}
${optionalString (cfg.hostAddress6 != null) ''
echo "Setting route6 to host for ${name}"
ip -6 route add ${cfg.hostAddress6} dev ${name}
''}
''
);
in
pkgs.writeScript "container-init"
''
#! ${pkgs.runtimeShell} -e
# Initialise the container side of the veth pair.
if [ "$PRIVATE_NETWORK" = 1 ]; then
ip link set host0 name eth0
ip link set dev eth0 up
if [ -n "$LOCAL_ADDRESS" ]; then
ip addr add $LOCAL_ADDRESS dev eth0
fi
if [ -n "$LOCAL_ADDRESS6" ]; then
ip -6 addr add $LOCAL_ADDRESS6 dev eth0
fi
if [ -n "$HOST_ADDRESS" ]; then
ip route add $HOST_ADDRESS dev eth0
ip route add default via $HOST_ADDRESS
fi
if [ -n "$HOST_ADDRESS6" ]; then
ip -6 route add $HOST_ADDRESS6 dev eth0
ip -6 route add default via $HOST_ADDRESS6
fi
${concatStringsSep "\n" (mapAttrsToList renderExtraVeth cfg.extraVeths)}
fi
# Start the regular stage 1 script.
exec "$1"
''
);
nspawnExtraVethArgs = (name: cfg: "--network-veth-extra=${name}");
startScript = cfg:
''
mkdir -p -m 0755 "$root/etc" "$root/var/lib"
mkdir -p -m 0700 "$root/var/lib/private" "$root/root" /run/containers
if ! [ -e "$root/etc/os-release" ]; then
touch "$root/etc/os-release"
fi
if ! [ -e "$root/etc/machine-id" ]; then
touch "$root/etc/machine-id"
fi
mkdir -p -m 0755 \
"/nix/var/nix/profiles/per-container/$INSTANCE" \
"/nix/var/nix/gcroots/per-container/$INSTANCE"
cp --remove-destination /etc/resolv.conf "$root/etc/resolv.conf"
if [ "$PRIVATE_NETWORK" = 1 ]; then
extraFlags+=" --network-veth"
if [ -n "$HOST_BRIDGE" ]; then
extraFlags+=" --network-bridge=$HOST_BRIDGE"
fi
if [ -n "$HOST_PORT" ]; then
OIFS=$IFS
IFS=","
for i in $HOST_PORT
do
extraFlags+=" --port=$i"
done
IFS=$OIFS
fi
fi
extraFlags+=" ${concatStringsSep " " (mapAttrsToList nspawnExtraVethArgs cfg.extraVeths)}"
for iface in $INTERFACES; do
extraFlags+=" --network-interface=$iface"
done
for iface in $MACVLANS; do
extraFlags+=" --network-macvlan=$iface"
done
# If the host is 64-bit and the container is 32-bit, add a
# --personality flag.
${optionalString (config.nixpkgs.localSystem.system == "x86_64-linux") ''
if [ "$(< ''${SYSTEM_PATH:-/nix/var/nix/profiles/per-container/$INSTANCE/system}/system)" = i686-linux ]; then
extraFlags+=" --personality=x86"
fi
''}
# Run systemd-nspawn without startup notification (we'll
# wait for the container systemd to signal readiness).
exec ${config.systemd.package}/bin/systemd-nspawn \
--keep-unit \
-M "$INSTANCE" -D "$root" $extraFlags \
$EXTRA_NSPAWN_FLAGS \
--notify-ready=yes \
--bind-ro=/nix/store \
--bind-ro=/nix/var/nix/db \
--bind-ro=/nix/var/nix/daemon-socket \
--bind="/nix/var/nix/profiles/per-container/$INSTANCE:/nix/var/nix/profiles" \
--bind="/nix/var/nix/gcroots/per-container/$INSTANCE:/nix/var/nix/gcroots" \
--setenv PRIVATE_NETWORK="$PRIVATE_NETWORK" \
--setenv HOST_BRIDGE="$HOST_BRIDGE" \
--setenv HOST_ADDRESS="$HOST_ADDRESS" \
--setenv LOCAL_ADDRESS="$LOCAL_ADDRESS" \
--setenv HOST_ADDRESS6="$HOST_ADDRESS6" \
--setenv LOCAL_ADDRESS6="$LOCAL_ADDRESS6" \
--setenv HOST_PORT="$HOST_PORT" \
--setenv PATH="$PATH" \
${if cfg.additionalCapabilities != null && cfg.additionalCapabilities != [] then
''--capability="${concatStringsSep " " cfg.additionalCapabilities}"'' else ""
} \
${if cfg.tmpfs != null && cfg.tmpfs != [] then
''--tmpfs=${concatStringsSep " --tmpfs=" cfg.tmpfs}'' else ""
} \
${containerInit cfg} "''${SYSTEM_PATH:-/nix/var/nix/profiles/system}/init"
'';
preStartScript = cfg:
''
# Clean up existing machined registration and interfaces.
machinectl terminate "$INSTANCE" 2> /dev/null || true
if [ "$PRIVATE_NETWORK" = 1 ]; then
ip link del dev "ve-$INSTANCE" 2> /dev/null || true
ip link del dev "vb-$INSTANCE" 2> /dev/null || true
fi
${concatStringsSep "\n" (
mapAttrsToList (name: cfg:
''ip link del dev ${name} 2> /dev/null || true ''
) cfg.extraVeths
)}
'';
postStartScript = (cfg:
let
ipcall = cfg: ipcmd: variable: attribute:
if cfg.${attribute} == null then
''
if [ -n "${variable}" ]; then
${ipcmd} add ${variable} dev $ifaceHost
fi
''
else
''${ipcmd} add ${cfg.${attribute}} dev $ifaceHost'';
renderExtraVeth = name: cfg:
if cfg.hostBridge != null then
''
# Add ${name} to bridge ${cfg.hostBridge}
ip link set dev ${name} master ${cfg.hostBridge} up
''
else
''
# Set IPs and routes for ${name}
${optionalString (cfg.hostAddress != null) ''
ip addr add ${cfg.hostAddress} dev ${name}
''}
${optionalString (cfg.hostAddress6 != null) ''
ip -6 addr add ${cfg.hostAddress6} dev ${name}
''}
${optionalString (cfg.localAddress != null) ''
ip route add ${cfg.localAddress} dev ${name}
''}
${optionalString (cfg.localAddress6 != null) ''
ip -6 route add ${cfg.localAddress6} dev ${name}
''}
'';
in
''
if [ "$PRIVATE_NETWORK" = 1 ]; then
if [ -z "$HOST_BRIDGE" ]; then
ifaceHost=ve-$INSTANCE
ip link set dev $ifaceHost up
${ipcall cfg "ip addr" "$HOST_ADDRESS" "hostAddress"}
${ipcall cfg "ip -6 addr" "$HOST_ADDRESS6" "hostAddress6"}
${ipcall cfg "ip route" "$LOCAL_ADDRESS" "localAddress"}
${ipcall cfg "ip -6 route" "$LOCAL_ADDRESS6" "localAddress6"}
fi
${concatStringsSep "\n" (mapAttrsToList renderExtraVeth cfg.extraVeths)}
fi
# Get the leader PID so that we can signal it in
# preStop. We can't use machinectl there because D-Bus
# might be shutting down. FIXME: in systemd 219 we can
# just signal systemd-nspawn to do a clean shutdown.
machinectl show "$INSTANCE" | sed 's/Leader=\(.*\)/\1/;t;d' > "/run/containers/$INSTANCE.pid"
''
);
serviceDirectives = cfg: {
ExecReload = pkgs.writeScript "reload-container"
''
#! ${pkgs.runtimeShell} -e
${pkgs.nixos-container}/bin/nixos-container run "$INSTANCE" -- \
bash --login -c "''${SYSTEM_PATH:-/nix/var/nix/profiles/system}/bin/switch-to-configuration test"
'';
SyslogIdentifier = "container %i";
EnvironmentFile = "-/etc/containers/%i.conf";
Type = "notify";
# Note that on reboot, systemd-nspawn returns 133, so this
# unit will be restarted. On poweroff, it returns 0, so the
# unit won't be restarted.
RestartForceExitStatus = "133";
SuccessExitStatus = "133";
Restart = "on-failure";
# Hack: we don't want to kill systemd-nspawn, since we call
# "machinectl poweroff" in preStop to shut down the
# container cleanly. But systemd requires sending a signal
# (at least if we want remaining processes to be killed
# after the timeout). So send an ignored signal.
KillMode = "mixed";
KillSignal = "WINCH";
DevicePolicy = "closed";
DeviceAllow = map (d: "${d.node} ${d.modifier}") cfg.allowedDevices;
};
system = config.nixpkgs.localSystem.system;
bindMountOpts = { name, config, ... }: {
options = {
mountPoint = mkOption {
example = "/mnt/usb";
type = types.str;
description = "Mount point on the container file system.";
};
hostPath = mkOption {
default = null;
example = "/home/alice";
type = types.nullOr types.str;
description = "Location of the host path to be mounted.";
};
isReadOnly = mkOption {
default = true;
type = types.bool;
description = "Determine whether the mounted path will be accessed in read-only mode.";
};
};
config = {
mountPoint = mkDefault name;
};
};
allowedDeviceOpts = { name, config, ... }: {
options = {
node = mkOption {
example = "/dev/net/tun";
type = types.str;
description = "Path to device node";
};
modifier = mkOption {
example = "rw";
type = types.str;
description = ''
Device node access modifier. Takes a combination
<literal>r</literal> (read), <literal>w</literal> (write), and
<literal>m</literal> (mknod). See the
<literal>systemd.resource-control(5)</literal> man page for more
information.'';
};
};
};
mkBindFlag = d:
let flagPrefix = if d.isReadOnly then " --bind-ro=" else " --bind=";
mountstr = if d.hostPath != null then "${d.hostPath}:${d.mountPoint}" else "${d.mountPoint}";
in flagPrefix + mountstr ;
mkBindFlags = bs: concatMapStrings mkBindFlag (lib.attrValues bs);
networkOptions = {
hostBridge = mkOption {
type = types.nullOr types.string;
default = null;
example = "br0";
description = ''
Put the host-side of the veth-pair into the named bridge.
Only one of hostAddress* or hostBridge can be given.
'';
};
forwardPorts = mkOption {
type = types.listOf (types.submodule {
options = {
protocol = mkOption {
type = types.str;
default = "tcp";
description = "The protocol specifier for port forwarding between host and container";
};
hostPort = mkOption {
type = types.int;
description = "Source port of the external interface on host";
};
containerPort = mkOption {
type = types.nullOr types.int;
default = null;
description = "Target port of container";
};
};
});
default = [];
example = [ { protocol = "tcp"; hostPort = 8080; containerPort = 80; } ];
description = ''
List of forwarded ports from host to container. Each forwarded port
is specified by protocol, hostPort and containerPort. By default,
protocol is tcp and hostPort and containerPort are assumed to be
the same if containerPort is not explicitly given.
'';
};
hostAddress = mkOption {
type = types.nullOr types.str;
default = null;
example = "10.231.136.1";
description = ''
The IPv4 address assigned to the host interface.
(Not used when hostBridge is set.)
'';
};
hostAddress6 = mkOption {
type = types.nullOr types.string;
default = null;
example = "fc00::1";
description = ''
The IPv6 address assigned to the host interface.
(Not used when hostBridge is set.)
'';
};
localAddress = mkOption {
type = types.nullOr types.str;
default = null;
example = "10.231.136.2";
description = ''
The IPv4 address assigned to the interface in the container.
If a hostBridge is used, this should be given with netmask to access
the whole network. Otherwise the default netmask is /32 and routing is
set up from localAddress to hostAddress and back.
'';
};
localAddress6 = mkOption {
type = types.nullOr types.string;
default = null;
example = "fc00::2";
description = ''
The IPv6 address assigned to the interface in the container.
If a hostBridge is used, this should be given with netmask to access
the whole network. Otherwise the default netmask is /128 and routing is
set up from localAddress6 to hostAddress6 and back.
'';
};
};
dummyConfig =
{
extraVeths = {};
additionalCapabilities = [];
allowedDevices = [];
hostAddress = null;
hostAddress6 = null;
localAddress = null;
localAddress6 = null;
tmpfs = null;
};
in
{
options = {
boot.isContainer = mkOption {
type = types.bool;
default = false;
description = ''
Whether this NixOS machine is a lightweight container running
in another NixOS system.
'';
};
boot.enableContainers = mkOption {
type = types.bool;
default = !config.boot.isContainer;
description = ''
Whether to enable support for nixos containers.
'';
};
containers = mkOption {
type = types.attrsOf (types.submodule (
{ config, options, name, ... }:
{
options = {
config = mkOption {
description = ''
A specification of the desired configuration of this
container, as a NixOS module.
'';
type = lib.mkOptionType {
name = "Toplevel NixOS config";
merge = loc: defs: (import ../../lib/eval-config.nix {
inherit system;
modules =
let extraConfig =
{ boot.isContainer = true;
networking.hostName = mkDefault name;
networking.useDHCP = false;
};
in [ extraConfig ] ++ (map (x: x.value) defs);
prefix = [ "containers" name ];
}).config;
};
};
path = mkOption {
type = types.path;
example = "/nix/var/nix/profiles/containers/webserver";
description = ''
As an alternative to specifying
<option>config</option>, you can specify the path to
the evaluated NixOS system configuration, typically a
symlink to a system profile.
'';
};
additionalCapabilities = mkOption {
type = types.listOf types.str;
default = [];
example = [ "CAP_NET_ADMIN" "CAP_MKNOD" ];
description = ''
Grant additional capabilities to the container. See the
capabilities(7) and systemd-nspawn(1) man pages for more
information.
'';
};
enableTun = mkOption {
type = types.bool;
default = false;
description = ''
Allows the container to create and setup tunnel interfaces
by granting the <literal>NET_ADMIN</literal> capability and
enabling access to <literal>/dev/net/tun</literal>.
'';
};
privateNetwork = mkOption {
type = types.bool;
default = false;
description = ''
Whether to give the container its own private virtual
Ethernet interface. The interface is called
<literal>eth0</literal>, and is hooked up to the interface
<literal>ve-<replaceable>container-name</replaceable></literal>
on the host. If this option is not set, then the
container shares the network interfaces of the host,
and can bind to any port on any interface.
'';
};
interfaces = mkOption {
type = types.listOf types.string;
default = [];
example = [ "eth1" "eth2" ];
description = ''
The list of interfaces to be moved into the container.
'';
};
macvlans = mkOption {
type = types.listOf types.str;
default = [];
example = [ "eth1" "eth2" ];
description = ''
The list of host interfaces from which macvlans will be
created. For each interface specified, a macvlan interface
will be created and moved to the container.
'';
};
extraVeths = mkOption {
type = with types; attrsOf (submodule { options = networkOptions; });
default = {};
description = ''
Extra veth-pairs to be created for the container
'';
};
autoStart = mkOption {
type = types.bool;
default = false;
description = ''
Whether the container is automatically started at boot-time.
'';
};
bindMounts = mkOption {
type = with types; loaOf (submodule bindMountOpts);
default = {};
example = { "/home" = { hostPath = "/home/alice";
isReadOnly = false; };
};
description =
''
An extra list of directories that is bound to the container.
'';
};
allowedDevices = mkOption {
type = with types; listOf (submodule allowedDeviceOpts);
default = [];
example = [ { node = "/dev/net/tun"; modifier = "rw"; } ];
description = ''
A list of device nodes to which the containers has access to.
'';
};
tmpfs = mkOption {
type = types.listOf types.str;
default = [];
example = [ "/var" ];
description = ''
Mounts a set of tmpfs file systems into the container.
Multiple paths can be specified.
Valid items must conform to the --tmpfs argument
of systemd-nspawn. See systemd-nspawn(1) for details.
'';
};
extraFlags = mkOption {
type = types.listOf types.str;
default = [];
example = [ "--drop-capability=CAP_SYS_CHROOT" ];
description = ''
Extra flags passed to the systemd-nspawn command.
See systemd-nspawn(1) for details.
'';
};
} // networkOptions;
config = mkMerge
[
(mkIf options.config.isDefined {
path = config.config.system.build.toplevel;
})
];
}));
default = {};
example = literalExample
''
{ webserver =
{ path = "/nix/var/nix/profiles/webserver";
};
database =
{ config =
{ config, pkgs, ... }:
{ services.postgresql.enable = true;
services.postgresql.package = pkgs.postgresql96;
system.nixos.stateVersion = "17.03";
};
};
}
'';
description = ''
A set of NixOS system configurations to be run as lightweight
containers. Each container appears as a service
<literal>container-<replaceable>name</replaceable></literal>
on the host system, allowing it to be started and stopped via
<command>systemctl</command>.
'';
};
};
config = mkIf (config.boot.enableContainers) (let
unit = {
description = "Container '%i'";
unitConfig.RequiresMountsFor = [ "/var/lib/containers/%i" ];
path = [ pkgs.iproute ];
environment.INSTANCE = "%i";
environment.root = "/var/lib/containers/%i";
preStart = preStartScript dummyConfig;
script = startScript dummyConfig;
postStart = postStartScript dummyConfig;
preStop =
''
pid="$(cat /run/containers/$INSTANCE.pid)"
if [ -n "$pid" ]; then
kill -RTMIN+4 "$pid"
fi
rm -f "/run/containers/$INSTANCE.pid"
'';
restartIfChanged = false;
serviceConfig = serviceDirectives dummyConfig;
};
in {
systemd.services = listToAttrs (filter (x: x.value != null) (
# The generic container template used by imperative containers
[{ name = "container@"; value = unit; }]
# declarative containers
++ (mapAttrsToList (name: cfg: nameValuePair "container@${name}" (let
config = cfg // (
if cfg.enableTun then
{
allowedDevices = cfg.allowedDevices
++ [ { node = "/dev/net/tun"; modifier = "rw"; } ];
additionalCapabilities = cfg.additionalCapabilities
++ [ "CAP_NET_ADMIN" ];
}
else {});
in
unit // {
preStart = preStartScript config;
script = startScript config;
postStart = postStartScript config;
serviceConfig = serviceDirectives config;
} // (
if config.autoStart then
{
wantedBy = [ "multi-user.target" ];
wants = [ "network.target" ];
after = [ "network.target" ];
restartTriggers = [ config.path ];
reloadIfChanged = true;
}
else {})
)) config.containers)
));
# Generate a configuration file in /etc/containers for each
# container so that container@.target can get the container
# configuration.
environment.etc =
let mkPortStr = p: p.protocol + ":" + (toString p.hostPort) + ":" + (if p.containerPort == null then toString p.hostPort else toString p.containerPort);
in mapAttrs' (name: cfg: nameValuePair "containers/${name}.conf"
{ text =
''
SYSTEM_PATH=${cfg.path}
${optionalString cfg.privateNetwork ''
PRIVATE_NETWORK=1
${optionalString (cfg.hostBridge != null) ''
HOST_BRIDGE=${cfg.hostBridge}
''}
${optionalString (length cfg.forwardPorts > 0) ''
HOST_PORT=${concatStringsSep "," (map mkPortStr cfg.forwardPorts)}
''}
${optionalString (cfg.hostAddress != null) ''
HOST_ADDRESS=${cfg.hostAddress}
''}
${optionalString (cfg.hostAddress6 != null) ''
HOST_ADDRESS6=${cfg.hostAddress6}
''}
${optionalString (cfg.localAddress != null) ''
LOCAL_ADDRESS=${cfg.localAddress}
''}
${optionalString (cfg.localAddress6 != null) ''
LOCAL_ADDRESS6=${cfg.localAddress6}
''}
''}
INTERFACES="${toString cfg.interfaces}"
MACVLANS="${toString cfg.macvlans}"
${optionalString cfg.autoStart ''
AUTO_START=1
''}
EXTRA_NSPAWN_FLAGS="${mkBindFlags cfg.bindMounts +
optionalString (cfg.extraFlags != [])
(" " + concatStringsSep " " cfg.extraFlags)}"
'';
}) config.containers;
# Generate /etc/hosts entries for the containers.
networking.extraHosts = concatStrings (mapAttrsToList (name: cfg: optionalString (cfg.localAddress != null)
''
${head (splitString "/" cfg.localAddress)} ${name}.containers
'') config.containers);
networking.dhcpcd.denyInterfaces = [ "ve-*" "vb-*" ];
services.udev.extraRules = optionalString config.networking.networkmanager.enable ''
# Don't manage interfaces created by nixos-container.
ENV{INTERFACE}=="v[eb]-*", ENV{NM_UNMANAGED}="1"
'';
environment.systemPackages = [ pkgs.nixos-container ];
});
}
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