src/system-update-generator/system-update-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2012 Lennart Poettering
   6 ***/
   7
   8 #include <errno.h>
   9 #include <unistd.h>
  10
  11 #include "fs-util.h"
  12 #include "log.h"
  13 #include "proc-cmdline.h"
  14 #include "special.h"
  15 #include "string-util.h"
  16 #include "util.h"
  17
  18 /*
  19  * Implements the logic described in systemd.offline-updates(7).
  20  */
  21
  22 static const char *arg_dest = "/tmp";
  23
  24 static int generate_symlink(void) {
  25         const char *p = NULL;
  26
  27         if (laccess("/system-update", F_OK) < 0) {
  28                 if (errno == ENOENT)
  29                         return 0;
  30
  31                 log_error_errno(errno, "Failed to check for system update: %m");
  32                 return -EINVAL;
  33         }
  34
  35         p = strjoina(arg_dest, "/" SPECIAL_DEFAULT_TARGET);
  36         if (symlink(SYSTEM_DATA_UNIT_PATH "/system-update.target", p) < 0)
  37                 return log_error_errno(errno, "Failed to create symlink %s: %m", p);
  38
  39         return 1;
  40 }
  41
  42 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
  43         assert(key);
  44
  45         /* Check if a run level is specified on the kernel command line. The
  46          * command line has higher priority than any on-disk configuration, so
  47          * it'll make any symlink we create moot.
  48          */
  49
  50         if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
  51                 log_warning("Offline system update overriden by kernel command line systemd.unit= setting");
  52         else if (!value && runlevel_to_target(key))
  53                 log_warning("Offline system update overriden by runlevel \"%s\" on the kernel command line", key);
  54
  55         return 0;
  56 }
  57
  58 int main(int argc, char *argv[]) {
  59         int r, k;
  60
  61         if (argc > 1 && argc != 4) {
  62                 log_error("This program takes three or no arguments.");
  63                 return EXIT_FAILURE;
  64         }
  65
  66         if (argc > 1)
  67                 arg_dest = argv[2];
  68
  69         log_set_prohibit_ipc(true);
  70         log_set_target(LOG_TARGET_AUTO);
  71         log_parse_environment();
  72         log_open();
  73
  74         umask(0022);
  75
  76         r = generate_symlink();
  77
  78         if (r > 0) {
  79                 k = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
  80                 if (k < 0)
  81                         log_warning_errno(k, "Failed to parse kernel command line, ignoring: %m");
  82         }
  83
  84         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
  85 }