[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: boot time on Linux
From: |
Bruno Haible |
Subject: |
Re: boot time on Linux |
Date: |
Thu, 10 Aug 2023 17:30:06 +0200 |
Natanael Copa wrote:
> There are machines without RTC (Raspberry PI for example), and in
> this case the time stamp may end up to be the same every reboot (if
> correctly set up it should save the shutdown time for the reboot and set
> time to this on next boot, but there is no guarantee).
Indeed, on a Raspi with Raspbian (Debian derivative), /var/run/utmp contains
a BOOT_TIME entry with time = 1970-01-01 00:00:05. Which is unusable.
The clock gets set during the boot process, apparently through NTP. Then,
some files get touched:
/var/lib/systemd/timers/stamp-apt-daily.timer
/var/lib/systemd/timers/stamp-apt-daily-upgrade.timer
/var/lib/apt/daily_lock
But I suspect that they may be touched at other moments than during boot.
Therefore here, the workaround with the file time stamps does not work.
But another workaround works:
2023-08-10 Bruno Haible <bruno@clisp.org>
readutmp: Fix the boot time returned on Raspbian.
* lib/readutmp.c (read_utmp_from_file): When the time of the BOOT_TIME
entry is very close to the Epoch, replace it with the time from the
"runlevel"/"~" entry.
diff --git a/lib/readutmp.c b/lib/readutmp.c
index b344d8294d..e383531474 100644
--- a/lib/readutmp.c
+++ b/lib/readutmp.c
@@ -369,6 +369,12 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
SET_UTMP_ENT ();
+# if defined __linux__ && !defined __ANDROID__
+ bool file_is_utmp = (strcmp (file, UTMP_FILE) == 0);
+ /* Timestamp of the "runlevel" entry, if any. */
+ struct timespec runlevel_ts = {0};
+# endif
+
void const *entry;
while ((entry = GET_UTMP_ENT ()) != NULL)
@@ -408,6 +414,13 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
struct UTMP_STRUCT_NAME const *ut = (struct UTMP_STRUCT_NAME const *)
entry;
# endif
+ struct timespec ts =
+ #if (HAVE_UTMPX_H ? 1 : HAVE_STRUCT_UTMP_UT_TV)
+ { .tv_sec = ut->ut_tv.tv_sec, .tv_nsec = ut->ut_tv.tv_usec * 1000 };
+ #else
+ { .tv_sec = ut->ut_time, .tv_nsec = 0 };
+ #endif
+
a = add_utmp (a, options,
UT_USER (ut), strnlen (UT_USER (ut), UT_USER_SIZE),
#if (HAVE_UTMPX_H ? HAVE_STRUCT_UTMPX_UT_ID :
HAVE_STRUCT_UTMP_UT_ID)
@@ -431,11 +444,7 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
#else
0,
#endif
- #if (HAVE_UTMPX_H ? 1 : HAVE_STRUCT_UTMP_UT_TV)
- (struct timespec) { .tv_sec = ut->ut_tv.tv_sec, .tv_nsec =
ut->ut_tv.tv_usec * 1000 },
- #else
- (struct timespec) { .tv_sec = ut->ut_time, .tv_nsec = 0 },
- #endif
+ ts,
#if (HAVE_UTMPX_H ? HAVE_STRUCT_UTMPX_UT_SESSION :
HAVE_STRUCT_UTMP_UT_SESSION)
ut->ut_session,
#else
@@ -443,6 +452,12 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
#endif
UT_EXIT_E_TERMINATION (ut), UT_EXIT_E_EXIT (ut)
);
+# if defined __linux__ && !defined __ANDROID__
+ if (file_is_utmp
+ && memcmp (UT_USER (ut), "runlevel", strlen ("runlevel") + 1) == 0
+ && memcmp (ut->ut_line, "~", strlen ("~") + 1) == 0)
+ runlevel_ts = ts;
+# endif
}
END_UTMP_ENT ();
@@ -450,9 +465,19 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
# if defined __linux__ && !defined __ANDROID__
/* On Alpine Linux, UTMP_FILE is not filled. It is always empty.
So, fake a BOOT_TIME entry, by getting the time stamp of a file that
- gets touched only during the boot process. */
+ gets touched only during the boot process.
+
+ On Raspbian, which runs on hardware without a real-time clock, during
boot,
+ 1. the clock gets set to 1970-01-01 00:00:00,
+ 2. an entry gets written into /var/run/utmp, with ut_type = BOOT_TIME,
+ ut_user = "reboot", ut_line = "~", time = 1970-01-01 00:00:05 or so,
+ 3. the clock gets set to a correct value through NTP,
+ 4. an entry gets written into /var/run/utmp, with
+ ut_user = "runlevel", ut_line = "~", time = correct value.
+ In this case, copy the time from the "runlevel" entry to the "reboot"
+ entry. */
if ((options & (READ_UTMP_USER_PROCESS | READ_UTMP_NO_BOOT_TIME)) == 0
- && strcmp (file, UTMP_FILE) == 0)
+ && file_is_utmp)
{
bool have_boot_time = false;
for (idx_t i = 0; i < a.filled; i++)
@@ -460,12 +485,16 @@ read_utmp_from_file (char const *file, idx_t *n_entries,
STRUCT_UTMP **utmp_buf,
struct gl_utmp *ut = &a.utmp[i];
if (UT_TYPE_BOOT_TIME (ut))
{
+ /* Workaround for Raspbian: */
+ if (ut->ut_ts.tv_sec <= 60 && runlevel_ts.tv_sec != 0)
+ ut->ut_ts = runlevel_ts;
have_boot_time = true;
break;
}
}
if (!have_boot_time)
{
+ /* Workaround for Alpine Linux: */
const char * const boot_touched_files[] =
{
"/var/lib/systemd/random-seed", /* seen on distros with systemd
*/
- Re: boot time on Linux, (continued)
- Re: boot time on Linux, Bruno Haible, 2023/08/10
- Re: boot time on Linux, Po Lu, 2023/08/10
- Re: boot time on Linux, Bruno Haible, 2023/08/10
- Re: boot time on Linux, Po Lu, 2023/08/10
- Re: boot time on Linux, Bruno Haible, 2023/08/10
- Re: boot time on Linux, Po Lu, 2023/08/11
- Re: boot time on Linux, Bruno Haible, 2023/08/10
- Re: boot time on Linux, Natanael Copa, 2023/08/10
- Re: boot time on Linux, Po Lu, 2023/08/10
- Re: boot time on Linux, Natanael Copa, 2023/08/10
- Re: boot time on Linux,
Bruno Haible <=
- Re: boot time on Linux, Bruno Haible, 2023/08/09
- Message not available
- Re: bug#64937: "who" reports funny dates, Thorsten Kukuk, 2023/08/10
- Re: bug#64937: "who" reports funny dates, Bruno Haible, 2023/08/10
- Message not available
- Re: bug#64937: "who" reports funny dates, Thorsten Kukuk, 2023/08/10
- Re: bug#64937: "who" reports funny dates, Paul Eggert, 2023/08/08
- Re: bug#64937: "who" reports funny dates, Bruno Haible, 2023/08/08
Re: bug#64937: "who" reports funny dates, Thorsten Kukuk, 2023/08/02