1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3 #include "bus-error.h"
4 #include "bus-locator.h"
5 #include "parse-util.h"
6 #include "path-util.h"
7 #include "proc-cmdline.h"
8 #include "signal-util.h"
9 #include "stat-util.h"
10 #include "systemctl-switch-root.h"
11 #include "systemctl-util.h"
12 #include "systemctl.h"
13
verb_switch_root(int argc,char * argv[],void * userdata)14 int verb_switch_root(int argc, char *argv[], void *userdata) {
15 _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
16 _cleanup_free_ char *cmdline_init = NULL;
17 const char *root, *init;
18 sd_bus *bus;
19 int r;
20
21 if (arg_transport != BUS_TRANSPORT_LOCAL)
22 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Cannot switch root remotely.");
23
24 if (argc < 2 || argc > 3)
25 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Wrong number of arguments.");
26
27 root = argv[1];
28
29 if (argc >= 3)
30 init = argv[2];
31 else {
32 r = proc_cmdline_get_key("init", 0, &cmdline_init);
33 if (r < 0)
34 log_debug_errno(r, "Failed to parse /proc/cmdline: %m");
35
36 init = cmdline_init;
37 }
38
39 init = empty_to_null(init);
40 if (init) {
41 const char *root_systemd_path = NULL, *root_init_path = NULL;
42
43 root_systemd_path = prefix_roota(root, "/" SYSTEMD_BINARY_PATH);
44 root_init_path = prefix_roota(root, init);
45
46 /* If the passed init is actually the same as the systemd binary, then let's suppress it. */
47 if (files_same(root_init_path, root_systemd_path, 0) > 0)
48 init = NULL;
49 }
50
51 /* Instruct PID1 to exclude us from its killing spree applied during the transition. Otherwise we
52 * would exit with a failure status even though the switch to the new root has succeed. */
53 assert(saved_argv);
54 assert(saved_argv[0]);
55 saved_argv[0][0] = '@';
56
57 r = acquire_bus(BUS_MANAGER, &bus);
58 if (r < 0)
59 return r;
60
61 /* If we are slow to exit after the root switch, the new systemd instance will send us a signal to
62 * terminate. Just ignore it and exit normally. This way the unit does not end up as failed. */
63 r = ignore_signals(SIGTERM);
64 if (r < 0)
65 log_warning_errno(r, "Failed to change disposition of SIGTERM to ignore: %m");
66
67 log_debug("Switching root - root: %s; init: %s", root, strna(init));
68
69 r = bus_call_method(bus, bus_systemd_mgr, "SwitchRoot", &error, NULL, "ss", root, init);
70 if (r < 0) {
71 (void) default_signals(SIGTERM);
72
73 return log_error_errno(r, "Failed to switch root: %s", bus_error_message(&error, r));
74 }
75
76 return 0;
77 }
78