nixpkgs/nixos/modules/virtualisation/nixos-container.pl

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#! @perl@
use strict;
use POSIX;
use File::Path;
use File::Slurp;
use Fcntl ':flock';
use Getopt::Long qw(:config gnu_getopt);
my $nsenter = "@utillinux@/bin/nsenter";
my $su = "@su@";
# Ensure a consistent umask.
umask 0022;
# Parse the command line.
sub showHelp {
print <<EOF;
Usage: nixos-container list
nixos-container create <container-name> [--system-path <path>] [--config <string>] [--ensure-unique-name] [--auto-start]
nixos-container destroy <container-name>
nixos-container start <container-name>
nixos-container stop <container-name>
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nixos-container status <container-name>
nixos-container update <container-name> [--config <string>]
nixos-container login <container-name>
nixos-container root-login <container-name>
nixos-container run <container-name> -- args...
nixos-container show-ip <container-name>
nixos-container show-host-key <container-name>
EOF
exit 0;
}
my $systemPath;
my $ensureUniqueName = 0;
my $autoStart = 0;
my $extraConfig;
GetOptions(
"help" => sub { showHelp() },
"ensure-unique-name" => \$ensureUniqueName,
"auto-start" => \$autoStart,
"system-path=s" => \$systemPath,
"config=s" => \$extraConfig
) or exit 1;
my $action = $ARGV[0] or die "$0: no action specified\n";
# Execute the selected action.
mkpath("/etc/containers", 0, 0755);
mkpath("/var/lib/containers", 0, 0700);
if ($action eq "list") {
foreach my $confFile (glob "/etc/containers/*.conf") {
$confFile =~ /\/([^\/]+).conf$/ or next;
print "$1\n";
}
exit 0;
}
my $containerName = $ARGV[1] or die "$0: no container name specified\n";
$containerName =~ /^[a-zA-Z0-9\-]+$/ or die "$0: invalid container name\n";
sub writeNixOSConfig {
my ($nixosConfigFile) = @_;
my $nixosConfig = <<EOF;
{ config, lib, pkgs, ... }:
with lib;
{ boot.isContainer = true;
networking.hostName = mkDefault "$containerName";
networking.useDHCP = false;
$extraConfig
}
EOF
write_file($nixosConfigFile, $nixosConfig);
}
if ($action eq "create") {
# Acquire an exclusive lock to prevent races with other
# invocations of nixos-container create.
my $lockFN = "/run/lock/nixos-container";
open(my $lock, '>>', $lockFN) or die "$0: opening $lockFN: $!";
flock($lock, LOCK_EX) or die "$0: could not lock $lockFN: $!";
my $confFile = "/etc/containers/$containerName.conf";
my $root = "/var/lib/containers/$containerName";
# Maybe generate a unique name.
if ($ensureUniqueName) {
my $base = $containerName;
for (my $nr = 0; ; $nr++) {
$containerName = "$base-$nr";
$confFile = "/etc/containers/$containerName.conf";
$root = "/var/lib/containers/$containerName";
last unless -e $confFile || -e $root;
}
}
die "$0: container $containerName already exists\n" if -e $confFile;
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# Due to interface name length restrictions, container names must
# be restricted too.
die "$0: container name $containerName is too long\n" if length $containerName > 11;
# Get an unused IP address.
my %usedIPs;
foreach my $confFile2 (glob "/etc/containers/*.conf") {
my $s = read_file($confFile2) or die;
$usedIPs{$1} = 1 if $s =~ /^HOST_ADDRESS=([0-9\.]+)$/m;
$usedIPs{$1} = 1 if $s =~ /^LOCAL_ADDRESS=([0-9\.]+)$/m;
}
my ($ipPrefix, $hostAddress, $localAddress);
for (my $nr = 1; $nr < 255; $nr++) {
$ipPrefix = "10.233.$nr";
$hostAddress = "$ipPrefix.1";
$localAddress = "$ipPrefix.2";
last unless $usedIPs{$hostAddress} || $usedIPs{$localAddress};
$ipPrefix = undef;
}
die "$0: out of IP addresses\n" unless defined $ipPrefix;
my @conf;
push @conf, "PRIVATE_NETWORK=1\n";
push @conf, "HOST_ADDRESS=$hostAddress\n";
push @conf, "LOCAL_ADDRESS=$localAddress\n";
push @conf, "AUTO_START=$autoStart\n";
write_file($confFile, \@conf);
close($lock);
print STDERR "host IP is $hostAddress, container IP is $localAddress\n";
# The per-container directory is restricted to prevent users on
# the host from messing with guest users who happen to have the
# same uid.
my $profileDir = "/nix/var/nix/profiles/per-container";
mkpath($profileDir, 0, 0700);
$profileDir = "$profileDir/$containerName";
mkpath($profileDir, 0, 0755);
# Build/set the initial configuration.
if (defined $systemPath) {
system("nix-env", "-p", "$profileDir/system", "--set", $systemPath) == 0
or die "$0: failed to set initial container configuration\n";
} else {
mkpath("$root/etc/nixos", 0, 0755);
my $nixosConfigFile = "$root/etc/nixos/configuration.nix";
writeNixOSConfig $nixosConfigFile;
system("nix-env", "-p", "$profileDir/system",
"-I", "nixos-config=$nixosConfigFile", "-f", "<nixpkgs/nixos>",
"--set", "-A", "system") == 0
or die "$0: failed to build initial container configuration\n";
}
print "$containerName\n" if $ensureUniqueName;
exit 0;
}
my $root = "/var/lib/containers/$containerName";
my $profileDir = "/nix/var/nix/profiles/per-container/$containerName";
my $gcRootsDir = "/nix/var/nix/gcroots/per-container/$containerName";
my $confFile = "/etc/containers/$containerName.conf";
if (!-e $confFile) {
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if ($action eq "destroy") {
exit 0;
} elsif ($action eq "status") {
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print "gone\n";
}
die "$0: container $containerName does not exist\n" ;
}
sub isContainerRunning {
my $status = `systemctl show 'container\@$containerName'`;
return $status =~ /ActiveState=active/;
}
sub stopContainer {
system("systemctl", "stop", "container\@$containerName") == 0
or die "$0: failed to stop container\n";
}
# Return the PID of the init process of the container.
sub getLeader {
my $s = `machinectl show "$containerName" -p Leader`;
chomp $s;
$s =~ /^Leader=(\d+)$/ or die "unable to get container's main PID\n";
return int($1);
}
# Run a command in the container.
sub runInContainer {
my @args = @_;
my $leader = getLeader;
exec($nsenter, "-t", $leader, "-m", "-u", "-i", "-n", "-p", "--", @args);
die "cannot run nsenter: $!\n";
}
# Remove a directory while recursively unmounting all mounted filesystems within
# that directory and unmounting/removing that directory afterwards as well.
#
# NOTE: If the specified path is a mountpoint, its contents will be removed,
# only mountpoints underneath that path will be unmounted properly.
sub safeRemoveTree {
my ($path) = @_;
system("find", $path, "-mindepth", "1", "-xdev",
"(", "-type", "d", "-exec", "mountpoint", "-q", "{}", ";", ")",
"-exec", "umount", "-fR", "{}", "+");
system("rm", "--one-file-system", "-rf", $path);
if (-e $path) {
system("umount", "-fR", $path);
system("rm", "--one-file-system", "-rf", $path);
}
}
if ($action eq "destroy") {
die "$0: cannot destroy declarative container (remove it from your configuration.nix instead)\n"
unless POSIX::access($confFile, &POSIX::W_OK);
stopContainer if isContainerRunning;
safeRemoveTree($profileDir) if -e $profileDir;
safeRemoveTree($gcRootsDir) if -e $gcRootsDir;
safeRemoveTree($root) if -e $root;
unlink($confFile) or die;
}
elsif ($action eq "start") {
system("systemctl", "start", "container\@$containerName") == 0
or die "$0: failed to start container\n";
}
elsif ($action eq "stop") {
stopContainer;
}
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elsif ($action eq "status") {
print isContainerRunning() ? "up" : "down", "\n";
}
elsif ($action eq "update") {
my $nixosConfigFile = "$root/etc/nixos/configuration.nix";
# FIXME: may want to be more careful about clobbering the existing
# configuration.nix.
writeNixOSConfig $nixosConfigFile if (defined $extraConfig && $extraConfig ne "");
system("nix-env", "-p", "$profileDir/system",
"-I", "nixos-config=$nixosConfigFile", "-f", "<nixpkgs/nixos>",
"--set", "-A", "system") == 0
or die "$0: failed to build container configuration\n";
if (isContainerRunning) {
print STDERR "reloading container...\n";
system("systemctl", "reload", "container\@$containerName") == 0
or die "$0: failed to reload container\n";
}
}
elsif ($action eq "login") {
exec("machinectl", "login", "--", $containerName);
}
elsif ($action eq "root-login") {
runInContainer("@su@", "root", "-l");
}
elsif ($action eq "run") {
shift @ARGV; shift @ARGV;
# Escape command.
my $s = join(' ', map { s/'/'\\''/g; "'$_'" } @ARGV);
runInContainer("@su@", "root", "-l", "-c", "exec " . $s);
}
elsif ($action eq "show-ip") {
my $s = read_file($confFile) or die;
$s =~ /^LOCAL_ADDRESS=([0-9\.]+)$/m or die "$0: cannot get IP address\n";
print "$1\n";
}
elsif ($action eq "show-host-key") {
my $fn = "$root/etc/ssh/ssh_host_ed25519_key.pub";
$fn = "$root/etc/ssh/ssh_host_ecdsa_key.pub" unless -e $fn;
exit 1 if ! -f $fn;
print read_file($fn);
}
else {
die "$0: unknown action $action\n";
}