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

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2012 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <unistd.h>
  22
  23 #include "fs-util.h"
  24 #include "log.h"
  25 #include "proc-cmdline.h"
  26 #include "special.h"
  27 #include "string-util.h"
  28 #include "util.h"
  29
  30 /*
  31  * Implements the logic described in systemd.offline-updates(7).
  32  */
  33
  34 static const char *arg_dest = "/tmp";
  35
  36 static int generate_symlink(void) {
  37         const char *p = NULL;
  38
  39         if (laccess("/system-update", F_OK) < 0) {
  40                 if (errno == ENOENT)
  41                         return 0;
  42
  43                 log_error_errno(errno, "Failed to check for system update: %m");
  44                 return -EINVAL;
  45         }
  46
  47         p = strjoina(arg_dest, "/" SPECIAL_DEFAULT_TARGET);
  48         if (symlink(SYSTEM_DATA_UNIT_PATH "/system-update.target", p) < 0)
  49                 return log_error_errno(errno, "Failed to create symlink %s: %m", p);
  50
  51         return 1;
  52 }
  53
  54 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
  55         assert(key);
  56
  57         /* Check if a run level is specified on the kernel command line. The
  58          * command line has higher priority than any on-disk configuration, so
  59          * it'll make any symlink we create moot.
  60          */
  61
  62         if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
  63                 log_warning("Offline system update overriden by kernel command line systemd.unit= setting");
  64         else if (!value && runlevel_to_target(key))
  65                 log_warning("Offline system update overriden by runlevel \"%s\" on the kernel command line", key);
  66
  67         return 0;
  68 }
  69
  70 int main(int argc, char *argv[]) {
  71         int r, k;
  72
  73         if (argc > 1 && argc != 4) {
  74                 log_error("This program takes three or no arguments.");
  75                 return EXIT_FAILURE;
  76         }
  77
  78         if (argc > 1)
  79                 arg_dest = argv[2];
  80
  81         log_set_target(LOG_TARGET_SAFE);
  82         log_parse_environment();
  83         log_open();
  84
  85         umask(0022);
  86
  87         r = generate_symlink();
  88
  89         if (r > 0) {
  90                 k = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
  91                 if (k < 0)
  92                         log_warning_errno(k, "Failed to parse kernel command line, ignoring: %m");
  93         }
  94
  95         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
  96 }