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main: add a kernel command line option for setting the system clock early during boot

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This commit is contained in:
Lennart Poettering 2020-05-14 10:41:47 +02:00
parent 814872e925
commit 3753325bef
2 changed files with 42 additions and 0 deletions
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8
man/kernel-command-line.xml
View File

@ -459,6 +459,14 @@
of the <filename>systemd-firstboot.service</filename> system service but has no effect on the
condition check (see above).</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.clock-usec=</varname></term>
<listitem><para>Takes a decimal, numeric timestamp in µs since January 1st 1970, 00:00am, to set the
system clock to. The system time is set to the specified timestamp early during
boot. It is not propagated to the hardware clock (RTC).</para></listitem>
</varlistentry>
</variablelist>
</refsect1>

34
src/core/main.c
View File

@ -146,6 +146,7 @@ static EmergencyAction arg_cad_burst_action;
static OOMPolicy arg_default_oom_policy;
static CPUSet arg_cpu_affinity;
static NUMAPolicy arg_numa_policy;
static usec_t arg_clock_usec;
/* A copy of the original environment block */
static char **saved_env = NULL;
@ -491,6 +492,15 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
(void) parse_path_argument_and_warn(value, false, &arg_watchdog_device);
} else if (proc_cmdline_key_streq(key, "systemd.clock_usec")) {
if (proc_cmdline_value_missing(key, value))
return 0;
r = safe_atou64(value, &arg_clock_usec);
if (r < 0)
log_warning_errno(r, "Failed to parse systemd.clock_usec= argument, ignoring: %s", value);
} else if (streq(key, "quiet") && !value) {
if (arg_show_status == _SHOW_STATUS_INVALID)
@ -1504,6 +1514,9 @@ static int become_shutdown(
static void initialize_clock(void) {
int r;
/* This is called very early on, before we parse the kernel command line or otherwise figure out why
* we are running, but only once. */
if (clock_is_localtime(NULL) > 0) {
int min;
@ -1542,6 +1555,25 @@ static void initialize_clock(void) {
log_info("System time before build time, advancing clock.");
}
static void apply_clock_update(void) {
struct timespec ts;
/* This is called later than initialize_clock(), i.e. after we parsed configuration files/kernel
* command line and such. */
if (arg_clock_usec == 0)
return;
if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, arg_clock_usec)) < 0)
log_error_errno(errno, "Failed to set system clock to time specified on kernel command line: %m");
else {
char buf[FORMAT_TIMESTAMP_MAX];
log_info("Set system clock to %s, as specified on the kernel command line.",
format_timestamp(buf, sizeof(buf), arg_clock_usec));
}
}
static void initialize_coredump(bool skip_setup) {
#if ENABLE_COREDUMP
if (getpid_cached() != 1)
@ -2658,6 +2690,8 @@ int main(int argc, char *argv[]) {
assert_se(chdir("/") == 0);
if (arg_action == ACTION_RUN) {
/* Apply the systemd.clock_usec= kernel command line switch */
apply_clock_update();
/* A core pattern might have been specified via the cmdline. */
initialize_core_pattern(skip_setup);