ce6b83128e
Keep the working directory (and umask) inherited from
the parent. Otherwise, it's impossible to control
the working directory of the daemon (from systemd, for
example).
Furthermoer, bitmonerod attempts to create logging directories and files
*in current working directory*. This fails due to permission denied and
generates a (caught, nonfatal) exception. Below is the strace with this
patch applied (so, no `chdir("/")`), showing successful opens at `log/`
relative path. Without this patch they fail (sorry, didn't save the
trace).
```
28911 getcwd("/.../bitmonero", 128) = 25
28911 stat64("/var/lib/bitmonero/.bitmonero", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
28911 stat64("/etc/bitmonerod.conf", {st_mode=S_IFREG|0644, st_size=244, ...}) = 0
28911 open("/etc/bitmonerod.conf", O_RDONLY|O_LARGEFILE) = 3
28911 open("/var/log/bitmonero/bitmonero.log", O_WRONLY|O_CREAT|O_APPEND|O_LARGEFILE, 0666) = 3
28911 stat64("log", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
28911 stat64("log/dbg", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
28911 open("log/dbg/main.log", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 4
```
The reasoning of chdir("/") in order to prevent the daemon from holding
a filesystem in busy state is not compelling at all: the choice of
working directory for the daemon is the user's business not the
daemon's.
95 lines
2.2 KiB
C++
95 lines
2.2 KiB
C++
// Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include "daemonizer/posix_fork.h"
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#include "misc_log_ex.h"
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#include <cstdlib>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdexcept>
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#include <string>
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#include <sys/stat.h>
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namespace posix {
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namespace {
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void quit(std::string const & message)
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{
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LOG_ERROR(message);
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throw std::runtime_error(message);
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}
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}
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void fork()
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{
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// Fork the process and have the parent exit. If the process was started
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// from a shell, this returns control to the user. Forking a new process is
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// also a prerequisite for the subsequent call to setsid().
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if (pid_t pid = ::fork())
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{
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if (pid > 0)
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{
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// We're in the parent process and need to exit.
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//
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// When the exit() function is used, the program terminates without
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// invoking local variables' destructors. Only global variables are
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// destroyed.
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exit(0);
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}
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else
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{
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quit("First fork failed");
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}
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}
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// Make the process a new session leader. This detaches it from the
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// terminal.
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setsid();
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// A second fork ensures the process cannot acquire a controlling terminal.
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if (pid_t pid = ::fork())
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{
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if (pid > 0)
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{
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exit(0);
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}
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else
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{
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quit("Second fork failed");
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}
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}
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// Close the standard streams. This decouples the daemon from the terminal
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// that started it.
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close(0);
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close(1);
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close(2);
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// We don't want the daemon to have any standard input.
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if (open("/dev/null", O_RDONLY) < 0)
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{
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quit("Unable to open /dev/null");
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}
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// Send standard output to a log file.
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const char* output = "/tmp/bitmonero.daemon.stdout.stderr";
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const int flags = O_WRONLY | O_CREAT | O_APPEND;
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const mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
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if (open(output, flags, mode) < 0)
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{
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quit("Unable to open output file: " + std::string(output));
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}
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// Also send standard error to the same log file.
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if (dup(1) < 0)
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{
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quit("Unable to dup output descriptor");
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}
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}
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} // namespace posix
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