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

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <unistd.h>
   5
   6 #include "fs-util.h"
   7 #include "generator.h"
   8 #include "initrd-util.h"
   9 #include "log.h"
  10 #include "path-util.h"
  11 #include "proc-cmdline.h"
  12 #include "special.h"
  13 #include "string-util.h"
  14 #include "unit-file.h"
  15
  16 /*
  17  * Implements the logic described in systemd.offline-updates(7).
  18  */
  19
  20 static const char *arg_dest = NULL;
  21
  22 static int generate_symlink(void) {
  23         FOREACH_STRING(p, "/system-update", "/etc/system-update") {
  24                 if (laccess(p, F_OK) >= 0) {
  25                         _cleanup_free_ char *j = NULL;
  26
  27                         j = path_join(arg_dest, SPECIAL_DEFAULT_TARGET);
  28                         if (!j)
  29                                 return log_oom();
  30
  31                         if (symlink(SYSTEM_DATA_UNIT_DIR "/system-update.target", j) < 0)
  32                                 return log_error_errno(errno, "Failed to create symlink %s: %m", j);
  33
  34                         return 1;
  35                 }
  36
  37                 if (errno != ENOENT)
  38                         log_warning_errno(errno, "Failed to check if %s symlink exists, ignoring: %m", p);
  39         }
  40
  41         return 0;
  42 }
  43
  44 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
  45         assert(key);
  46
  47         /* Check if a run level is specified on the kernel command line. The
  48          * command line has higher priority than any on-disk configuration, so
  49          * it'll make any symlink we create moot.
  50          */
  51
  52         if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
  53                 log_warning("Offline system update overridden by kernel command line systemd.unit= setting");
  54         else if (!value && runlevel_to_target(key))
  55                 log_warning("Offline system update overridden by runlevel \"%s\" on the kernel command line", key);
  56
  57         return 0;
  58 }
  59
  60 static int run(const char *dest, const char *dest_early, const char *dest_late) {
  61         int r;
  62
  63         assert_se(arg_dest = dest_early);
  64
  65         if (in_initrd()) {
  66                 log_debug("Skipping generator, running in the initrd.");
  67                 return EXIT_SUCCESS;
  68         }
  69
  70         r = generate_symlink();
  71         if (r <= 0)
  72                 return r;
  73
  74         /* We parse the command line only to emit warnings. */
  75         r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
  76         if (r < 0)
  77                 log_warning_errno(r, "Failed to parse kernel command line, ignoring: %m");
  78
  79         return 0;
  80 }
  81
  82 DEFINE_MAIN_GENERATOR_FUNCTION(run);