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

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