nixpkgs/nixos/modules/virtualisation/lxd-agent.nix

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{ config, lib, pkgs, ... }:
let
cfg = config.virtualisation.lxd.agent;
# the lxd agent is provided by the lxd daemon through a virtiofs or 9p mount
# this is a port of the distrobuilder lxd-agent generator
# https://github.com/lxc/distrobuilder/blob/f77300bf7d7d5707b08eaf8a434d647d1ba81b5d/generators/lxd-agent.go#L18-L55
preStartScript = ''
PREFIX="/run/lxd_agent"
mount_virtiofs() {
mount -t virtiofs config "$PREFIX/.mnt" >/dev/null 2>&1
}
mount_9p() {
modprobe 9pnet_virtio >/dev/null 2>&1 || true
mount -t 9p config "$PREFIX/.mnt" -o access=0,trans=virtio,size=1048576 >/dev/null 2>&1
}
fail() {
umount -l "$PREFIX" >/dev/null 2>&1 || true
rmdir "$PREFIX" >/dev/null 2>&1 || true
echo "$1"
exit 1
}
# Setup the mount target.
umount -l "$PREFIX" >/dev/null 2>&1 || true
mkdir -p "$PREFIX"
mount -t tmpfs tmpfs "$PREFIX" -o mode=0700,size=50M
mkdir -p "$PREFIX/.mnt"
# Try virtiofs first.
mount_virtiofs || mount_9p || fail "Couldn't mount virtiofs or 9p, failing."
# Copy the data.
cp -Ra "$PREFIX/.mnt/"* "$PREFIX"
# Unmount the temporary mount.
umount "$PREFIX/.mnt"
rmdir "$PREFIX/.mnt"
# Fix up permissions.
chown -R root:root "$PREFIX"
'';
in {
meta.maintainers = with lib.maintainers; [ adamcstephens ];
options = {
virtualisation.lxd.agent.enable = lib.mkEnableOption (lib.mdDoc "Enable LXD agent");
};
config = lib.mkIf cfg.enable {
# https://github.com/lxc/distrobuilder/blob/f77300bf7d7d5707b08eaf8a434d647d1ba81b5d/generators/lxd-agent.go#L108-L125
systemd.services.lxd-agent = {
enable = true;
wantedBy = [ "multi-user.target" ];
path = [ pkgs.kmod pkgs.util-linux ];
preStart = preStartScript;
# avoid killing nixos-rebuild switch when executed through lxc exec
stopIfChanged = false;
unitConfig = {
Description = "LXD - agent";
Documentation = "https://documentation.ubuntu.com/lxd/en/latest";
ConditionPathExists = "/dev/virtio-ports/org.linuxcontainers.lxd";
Before = lib.optionals config.services.cloud-init.enable [ "cloud-init.target" "cloud-init.service" "cloud-init-local.service" ];
DefaultDependencies = "no";
StartLimitInterval = "60";
StartLimitBurst = "10";
};
serviceConfig = {
Type = "notify";
WorkingDirectory = "-/run/lxd_agent";
ExecStart = "/run/lxd_agent/lxd-agent";
Restart = "on-failure";
RestartSec = "5s";
};
};
systemd.paths.lxd-agent = {
enable = true;
wantedBy = [ "multi-user.target" ];
pathConfig.PathExists = "/dev/virtio-ports/org.linuxcontainers.lxd";
};
};
}