What causes "Failed to read --server process uid" in rustdesk/rustdesk?

Rerun the command — the race is transient

Failed to read --server process uid

Error message

Failed to read --server process uid

What it means

While enumerating `--server` processes to find their uids, a process's user id could not be read (process.user_id() returned None). The code intentionally fails rather than silently skipping, because an unmatched key process would break stable uid-based target selection for root CLI commands.

Source

Thrown at src/ipc.rs:1399

    let mut server_uids = Vec::new();
    for process in sys.processes().values() {
        if process.pid() == current_pid {
            continue;
        }
        if process.cmd().get(1).map_or(true, |arg| arg != "--server") {
            continue;
        }
        let Ok(process_path) = std::fs::canonicalize(process.exe()) else {
            continue;
        };
        if process_path != current_exe_path {
            continue;
        }
        let Some(uid) = process.user_id().map(|uid| **uid as u32) else {
            // Root CLI management commands need a stable matching `--server` target.
            // If this key process races during enumeration, failing the command is clearer
            // than silently skipping it; `--server` is not expected to exit frequently.
            bail!("Failed to read --server process uid");
        };
        server_uids.push(uid);
    }
    Ok(server_uids)
}

#[cfg(any(target_os = "linux", target_os = "macos"))]
fn user_main_ipc_server_uid() -> ResultType<u32> {
    let server_uids = running_server_uids_for_current_exe()?;
    #[cfg(target_os = "linux")]
    let prefer_root = crate::platform::linux::is_login_screen_wayland();
    #[cfg(target_os = "macos")]
    let prefer_root = false;
    select_server_uid_for_user_main_ipc(&server_uids, active_uid(), prefer_root)
}

pub async fn connect(ms_timeout: u64, postfix: &str) -> ResultType<ConnectionTmpl<ConnClient>> {
    #[cfg(any(target_os = "linux", target_os = "macos"))]

View on GitHub (pinned to 91c9fccbb0)

Solutions

Rerun the command — the race is transient
Check /proc permissions (hidepid mount option) if it reproduces
Ensure the RustDesk service is not being restarted concurrently
Run the enumeration with sufficient privileges to read process uids

Example fix

// before
let uids = running_server_uids_for_current_exe()?;
// after
let uids = match running_server_uids_for_current_exe() {
    Ok(u) => u,
    Err(e) if e.to_string().contains("Failed to read --server process uid") => {
        std::thread::sleep(std::time::Duration::from_millis(200));
        running_server_uids_for_current_exe()?
    }
    Err(e) => return Err(e),
};

Defensive patterns

Strategy: retry

Try / catch

match running_server_uids_for_current_exe() {
    Ok(u) => u,
    Err(e) if e.to_string().contains("uid") => {
        std::thread::sleep(Duration::from_millis(200));
        running_server_uids_for_current_exe()?
    }
    Err(e) => return Err(e),
}

Prevention

Don't restart the service concurrently with management commands
Check /proc hidepid settings in hardened environments
Run with privileges sufficient to read process uids

When it happens

Trigger: A `--server` process matched by exe path disappears or its metadata becomes unreadable mid-enumeration (race with process exit), or the OS denies uid access for that process.

Common situations: Service being restarted exactly while a management command runs; restricted /proc permissions in hardened environments (hidepid) or containers limiting process metadata access.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

AI-assisted analysis of rustdesk/rustdesk@91c9fccbb0 (2026-09-10). Data as JSON: /api/errors/945817267300354f. Report an issue: GitHub.