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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include "bus-error.h"
#include "bus-locator.h"
#include "parse-util.h"
#include "path-util.h"
#include "proc-cmdline.h"
#include "signal-util.h"
#include "stat-util.h"
#include "systemctl-switch-root.h"
#include "systemctl-util.h"
#include "systemctl.h"
int switch_root(int argc, char *argv[], void *userdata) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_free_ char *cmdline_init = NULL;
const char *root, *init;
sd_bus *bus;
int r;
if (arg_transport != BUS_TRANSPORT_LOCAL)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Cannot switch root remotely.");
if (argc < 2 || argc > 3)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Wrong number of arguments.");
root = argv[1];
if (argc >= 3)
init = argv[2];
else {
r = proc_cmdline_get_key("init", 0, &cmdline_init);
if (r < 0)
log_debug_errno(r, "Failed to parse /proc/cmdline: %m");
init = cmdline_init;
}
init = empty_to_null(init);
if (init) {
const char *root_systemd_path = NULL, *root_init_path = NULL;
root_systemd_path = prefix_roota(root, "/" SYSTEMD_BINARY_PATH);
root_init_path = prefix_roota(root, init);
/* If the passed init is actually the same as the systemd binary, then let's suppress it. */
if (files_same(root_init_path, root_systemd_path, 0) > 0)
init = NULL;
}
/* Instruct PID1 to exclude us from its killing spree applied during the transition. Otherwise we
* would exit with a failure status even though the switch to the new root has succeed. */
assert(saved_argv);
assert(saved_argv[0]);
saved_argv[0][0] = '@';
r = acquire_bus(BUS_MANAGER, &bus);
if (r < 0)
return r;
/* If we are slow to exit after the root switch, the new systemd instance will send us a signal to
* terminate. Just ignore it and exit normally. This way the unit does not end up as failed. */
r = ignore_signals(SIGTERM, -1);
if (r < 0)
log_warning_errno(r, "Failed to change disposition of SIGTERM to ignore: %m");
log_debug("Switching root - root: %s; init: %s", root, strna(init));
r = bus_call_method(bus, bus_systemd_mgr, "SwitchRoot", &error, NULL, "ss", root, init);
if (r < 0) {
(void) default_signals(SIGTERM, -1);
return log_error_errno(r, "Failed to switch root: %s", bus_error_message(&error, r));
}
return 0;
}
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