tsiry-sandratraina.com
Headless Rust gRPC daemon to drive Bluetooth, HLS/DASH playback, and snapcast/shairport-sync/squeezelite on Raspberry Pi audio rigs.
Embed systemd --user unit template + `zerod service` installer
Adds three subcommands so the Pi/SBC user flow is a copy-paste from
README rather than hand-writing a service file:
zerod service install # writes ~/.config/systemd/user/zerod.service
zerod service uninstall # removes it
zerod service path # prints where it would land
The unit template lives at assets/zerod.service.in and is embedded via
include_str!. `service install` substitutes {{exec_start}} with
current_exe() (canonicalised), writes atomically via tempfile + rename,
and prints the systemctl --user follow-up commands plus a loginctl
enable-linger hint so it survives logout.
Linux-only — non-Linux builds expose the subcommand but every action
returns "zerod service: linux only" rather than producing a unit file
no one can use.
author
Tsiry Sandratraina
date
(Jun 10, 2026, 11:25 PM +0300)
commit
2156e69d
2156e69d5da79e7177e025ad7d28eb0f0f53657b
parent
1c4b62e8
1c4b62e887ee8bf3d4e9c4a6078ed45e7b7edd1e
+179
+28
assets/zerod.service.in
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assets/zerod.service.in
···
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# zerod user service — generated by `zerod service install`.
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# To override any field without editing this file, drop a snippet at
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# ~/.config/systemd/user/zerod.service.d/override.conf
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[Unit]
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Description=zerod headless audio / Bluetooth / systemd control daemon
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Documentation=https://tangled.org/tsiry-sandratraina.com/zerod
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After=network-online.target pipewire.service wireplumber.service
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Wants=network-online.target
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[Service]
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Type=simple
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ExecStart={{exec_start}}
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Restart=on-failure
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RestartSec=5
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# Pin the bearer token via env so the random fallback isn't used at startup.
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# Either set it inline here:
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# Environment=ZEROD_BEARER_TOKEN=changeme
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# or — better — in a drop-in that's not regenerated by `service install`:
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# ~/.config/systemd/user/zerod.service.d/override.conf
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#
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# Configuration files (bind address, systemd unit allowlist, managed
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# config registry) live in ~/.config/zerod/zerod.toml — see
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# `zerod.toml.example` for the schema.
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[Install]
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WantedBy=default.target
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src/main.rs
+63
src/main.rs
···
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use tonic::Request;
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use zerod_proto::v1alpha1 as pb;
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mod service;
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#[derive(Parser)]
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#[command(name = "zerod", version, about = "headless audio/bluetooth/systemd control daemon")]
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struct Cli {
···
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/// System volume control via ALSA mixer (client).
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#[command(subcommand)]
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Volume(VolumeCmd),
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/// Manage zerod's own systemd --user unit (Linux only).
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#[command(subcommand)]
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Service(ServiceCmd),
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}
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#[derive(Subcommand)]
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enum ServiceCmd {
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/// Write ~/.config/systemd/user/zerod.service pointing at this binary.
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Install {
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/// Overwrite an existing unit file.
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#[arg(long)]
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force: bool,
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},
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/// Remove ~/.config/systemd/user/zerod.service.
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Uninstall,
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/// Print where the unit file would be installed.
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Path,
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}
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#[derive(Subcommand)]
···
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Some(Command::Config(cmd)) => run_config(&cli.host, cli.port, cli.bearer_token, cmd).await,
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Some(Command::System(cmd)) => run_system(&cli.host, cli.port, cli.bearer_token, cmd).await,
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Some(Command::Volume(cmd)) => run_volume(&cli.host, cli.port, cli.bearer_token, cmd).await,
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Some(Command::Service(cmd)) => run_service(cmd),
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}
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}
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fn run_service(cmd: ServiceCmd) -> Result<()> {
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match cmd {
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ServiceCmd::Install { force } => {
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let path = service::install(force)?;
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println!("Wrote {}", path.display());
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println!();
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println!("Next steps:");
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println!(" systemctl --user daemon-reload");
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println!(" systemctl --user enable --now zerod.service");
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println!();
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println!("Then check it's healthy:");
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println!(" systemctl --user status zerod.service");
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println!(" journalctl --user -u zerod.service -f");
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println!();
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println!("So the service survives logout / starts on boot:");
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println!(" sudo loginctl enable-linger \"$USER\"");
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println!();
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println!("Pin the bearer token so the random one isn't used at startup:");
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println!(" systemctl --user edit zerod.service");
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println!(" # then add: [Service]\\n Environment=ZEROD_BEARER_TOKEN=…");
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Ok(())
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}
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ServiceCmd::Uninstall => match service::uninstall()? {
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Some(path) => {
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println!("Removed {}", path.display());
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println!();
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println!("Tell systemd to forget it:");
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println!(" systemctl --user disable --now zerod.service");
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println!(" systemctl --user daemon-reload");
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Ok(())
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}
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None => {
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println!("No unit file installed at {}", service::unit_path()?.display());
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Ok(())
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}
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},
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ServiceCmd::Path => {
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println!("{}", service::unit_path()?.display());
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Ok(())
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}
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}
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}
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+88
src/service.rs
+88
src/service.rs
···
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//! `zerod service {install,uninstall,path}` — manage zerod's own systemd
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//! user-unit. Linux-only: on other platforms the CLI surfaces a clear error
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//! rather than producing a unit file no one can use.
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#[cfg(target_os = "linux")]
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mod imp {
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use anyhow::{anyhow, Context, Result};
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use std::path::PathBuf;
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const TEMPLATE: &str = include_str!("../assets/zerod.service.in");
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const UNIT_NAME: &str = "zerod.service";
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/// `$XDG_CONFIG_HOME/systemd/user/zerod.service` or, when XDG isn't
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/// set, `~/.config/systemd/user/zerod.service`.
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pub fn unit_path() -> Result<PathBuf> {
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let base = match std::env::var_os("XDG_CONFIG_HOME") {
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Some(v) if !v.is_empty() => PathBuf::from(v),
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_ => {
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let home = std::env::var_os("HOME")
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.filter(|v| !v.is_empty())
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.ok_or_else(|| anyhow!("HOME is not set"))?;
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PathBuf::from(home).join(".config")
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}
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};
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Ok(base.join("systemd").join("user").join(UNIT_NAME))
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}
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pub fn install(force: bool) -> Result<PathBuf> {
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let exe = std::env::current_exe().context("resolve current_exe()")?;
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let exe = exe
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.canonicalize()
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.unwrap_or(exe); // best-effort canonicalise; symlinks → real path
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let exe_str = exe
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.to_str()
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.ok_or_else(|| anyhow!("current_exe path is not UTF-8: {exe:?}"))?;
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let path = unit_path()?;
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if path.exists() && !force {
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return Err(anyhow!(
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"{} already exists — pass --force to overwrite",
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path.display()
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));
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}
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let parent = path
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.parent()
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.ok_or_else(|| anyhow!("unit path has no parent: {}", path.display()))?;
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std::fs::create_dir_all(parent)
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.with_context(|| format!("mkdir -p {}", parent.display()))?;
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let rendered = TEMPLATE.replace("{{exec_start}}", exe_str);
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let tmp = path.with_extension("service.tmp");
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std::fs::write(&tmp, rendered)
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.with_context(|| format!("write {}", tmp.display()))?;
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std::fs::rename(&tmp, &path)
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.with_context(|| format!("rename {} → {}", tmp.display(), path.display()))?;
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Ok(path)
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}
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pub fn uninstall() -> Result<Option<PathBuf>> {
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let path = unit_path()?;
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if !path.exists() {
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return Ok(None);
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}
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std::fs::remove_file(&path)
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.with_context(|| format!("rm {}", path.display()))?;
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Ok(Some(path))
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}
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}
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#[cfg(not(target_os = "linux"))]
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mod imp {
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use anyhow::{bail, Result};
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use std::path::PathBuf;
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pub fn unit_path() -> Result<PathBuf> {
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bail!("zerod service: linux only")
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}
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pub fn install(_force: bool) -> Result<PathBuf> {
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bail!("zerod service: linux only")
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}
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pub fn uninstall() -> Result<Option<PathBuf>> {
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bail!("zerod service: linux only")
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}
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}
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pub use imp::{install, uninstall, unit_path};