update_engine/main.cc

// Copyright 2012 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <sys/stat.h>
#include <sys/types.h>
#include <xz.h>

#include <base/at_exit.h>
#include <base/command_line.h>
#include <base/logging.h>
#include <brillo/flag_helper.h>

#include "update_engine/common/daemon_base.h"
#include "update_engine/common/logging.h"
#include "update_engine/common/subprocess.h"
#include "update_engine/common/terminator.h"
#include "update_engine/common/utils.h"

using std::string;

int main(int argc, char** argv) {
  DEFINE_bool(logtofile, false, "Write logs to a file in log_dir.");
  DEFINE_bool(logtostderr, false,
              "Write logs to stderr instead of to a file in log_dir.");
  DEFINE_bool(foreground, false, "Don't daemon()ize; run in foreground.");

  chromeos_update_engine::Terminator::Init();
  brillo::FlagHelper::Init(argc, argv, "A/B Update Engine");

  // We have two logging flags "--logtostderr" and "--logtofile"; and the logic
  // to choose the logging destination is:
  // 1. --logtostderr --logtofile -> logs to both
  // 2. --logtostderr             -> logs to system debug
  // 3. --logtofile or no flags   -> logs to file
  bool log_to_system = FLAGS_logtostderr;
  bool log_to_file = FLAGS_logtofile || !FLAGS_logtostderr;
  chromeos_update_engine::SetupLogging(log_to_system, log_to_file);
  if (!FLAGS_foreground)
    PLOG_IF(FATAL, daemon(0, 0) == 1) << "daemon() failed";

  LOG(INFO) << "A/B Update Engine starting";

  // xz-embedded requires to initialize its CRC-32 table once on startup.
  xz_crc32_init();

  // Ensure that all written files have safe permissions.
  // This is a mask, so we _block_ all permissions for the group owner and other
  // users but allow all permissions for the user owner. We allow execution
  // for the owner so we can create directories.
  // Done _after_ log file creation.
  umask(S_IRWXG | S_IRWXO);

  auto daemon = chromeos_update_engine::DaemonBase::CreateInstance();
  int exit_code = daemon->Run();

  chromeos_update_engine::Subprocess::Get().FlushBufferedLogsAtExit();

  LOG(INFO) << "A/B Update Engine terminating with exit code " << exit_code;
  return exit_code;
}