[SOLVED] Fresh Slackware 15.0 install - system date/time not preserved after reboot.

random_guy · 03-21-2022, 10:34 AM

This weekend I decided to take the plunge and did a fresh install of Slackware-15.0. Everthing went well, except for one small thing - the system date/time (CST timezone) does not get preserved after reboots. Note, on Friday, with a 14.2 installation, there was no issue with the system date (time zone etc).

Things I've checked and tried so far.

-- BIOS date and time is correct, I double checked this.

-- Shows the correct date and time (CDT)
# hwclock --show
2022-03-20 14:33:02.293381-05:00

-- Off by 5 hrs
# date
Sun Mar 20 09:34:15 CDT 2022

# cat /etc/adjtime
0.000000 1647804661 0.000000
1647804661
LOCAL

# ls -ld /etc/*time*
-rw-r--r-- 1 root root 46 Mar 20 2022 /etc/adjtime
lrwxrwxrwx 1 root root 35 Mar 20 2022 /etc/localtime -> /usr/share/zoneinfo/America/Chicago

# cat /etc/hardwareclock
# /etc/hardwareclock
#
# Tells how the hardware clock time is stored.
# You should run timeconfig to edit this file.

localtime

Over the years, there have been similar reports of users of other distros having this problem. So I tried some of their tips, which didn't work:
1. Set hwclock
2. Set system date with, date command
3. Renamed /etc/adjtime
4. Reboot

Repeated the above steps 1 and 2 but left /etc/adjtime in place. This didn't work either.

Sorry for the long post. Did not want to waste anyones time

Any tips, comments or advice would be greatly appreciated.

TIA

subscrive · 03-22-2022, 04:03 AM

As root, enter "netdate time.nist.gov"

https://www.linux.org/threads/how-to...ackware.23706/

kjhambrick · 03-22-2022, 06:25 AM

Quote:

Originally Posted by subscrive

As root, enter "netdate time.nist.gov"

https://www.linux.org/threads/how-to...ackware.23706/

Yes, that works for me too but I also noticed what the O.P. ( random_guy ) says.

And I believe that his point is more-or-less 'Why doesn't the kernel set the System Time from the Hardware Clock' ?

IOW, how do I set the System Time at boot if my Server is isolated from the internet ?

-- kjh

GazL · 03-22-2022, 06:55 AM

A dodgy TZ environment variable can make 'date' show misleading information
e.g.

Code:

$ date
Tue 22 Mar 11:57:40 GMT 2022
$ TZ=':America/Chicago'  date
Tue 22 Mar 06:57:45 CDT 2022
$ TZ=CDT date
Tue 22 Mar 11:57:48 CDT 2022

... makes it look like CDT, but it's not.

Not saying that's your issue, but it's something to check.

random_guy · 03-22-2022, 10:05 AM

Thanks everyone for the responses.

@GazL, good call, I checked my TZ env. var and its not set. Any idea what sets this value in the environment or during install? I've never had to manipulate it in the past. I ran timeconfig this morning and selected US/Central it changed the zoneinfo(see below) but did not set the TZ variable. Thoughts?

$ ls -ld /etc/*time*
lrwxrwxrwx 1 root root 30 Mar 22 03:16 /etc/localtime -> /usr/share/zoneinfo/US/Central

@kjhambrick you are correct. I've never used an external time service to sync the clocks on my system. Not looking to change that.

GazL · 03-22-2022, 10:57 AM

The original idea was that you set TZ from your ~/.profile, which would then allow people on different continents to share a server while allowing each to work using their own local timezone. These days $TZ isn't used so much, especially as everyone has their own system, most likely running on their local timezone by default.

It's always worth checking whether it's set or not though when weird stuff happens. If anything was likely to set it, it'd probably be one of the Desktop Environment startup files, but if TZ is not set, then that's not your issue.

kjhambrick · 03-22-2022, 11:10 AM

random_guy --

Below is an sdiff of /etc/rc.d/rc.S 14.2 -vs- /etc/rc.d/rc.S 15.0 where hwclock is invoked at startup.

I pass the grep /proc/ioports test:

Code:

 grep " : rtc"  /proc/ioports
  0070-0077 : rtc0

And /etc/adjtime is newer than /etc/hardwareclock:

Code:

# [ /etc/adjtime -nt /etc/hardwareclock ] && echo "nt" || echo "not nt"
nt

The only diff I see us the '-a -z "$container" in the if-block ...

-- kjh

Code:

# /tmp/rc.S.14.2                                                                       # /etc/rc.d/rc.S
<<snip>>
# Set the system time from the hardware clock using hwclock --hctosys.                 # Set the system time from the hardware clock using hwclock --hctosys.
if [ -x /sbin/hwclock ]; then                                                       |  if [ -x /sbin/hwclock -a -z "$container" ]; then
  # Check for a broken motherboard RTC clock (where ioports for rtc are                  # Check for a broken motherboard RTC clock (where ioports for rtc are
  # unknown) to prevent hwclock causing a hang:                                          # unknown) to prevent hwclock causing a hang:
  if ! grep -q " : rtc" /proc/ioports ; then                                             if ! grep -q " : rtc" /proc/ioports ; then
    CLOCK_OPT="--directisa"                                                                CLOCK_OPT="--directisa"
  fi                                                                                     fi
  if [ /etc/adjtime -nt /etc/hardwareclock ]; then                                       if [ /etc/adjtime -nt /etc/hardwareclock ]; then
    if grep -q "^LOCAL" /etc/adjtime ; then                                                if grep -q "^LOCAL" /etc/adjtime ; then
      echo -n "Setting system time from the hardware clock (localtime):  "                   echo -n "Setting system time from the hardware clock (localtime):  "
    else                                                                                   else
      echo -n "Setting system time from the hardware clock (UTC):  "                         echo -n "Setting system time from the hardware clock (UTC):  "
    fi                                                                                     fi
    /sbin/hwclock $CLOCK_OPT --hctosys                                                     /sbin/hwclock $CLOCK_OPT --hctosys
  elif grep -wq "^localtime" /etc/hardwareclock 2> /dev/null ; then                      elif grep -wq "^localtime" /etc/hardwareclock 2> /dev/null ; then
    echo -n "Setting system time from the hardware clock (localtime):  "                   echo -n "Setting system time from the hardware clock (localtime):  "
    /sbin/hwclock $CLOCK_OPT --localtime --hctosys                                         /sbin/hwclock $CLOCK_OPT --localtime --hctosys
  else                                                                                   else
    echo -n "Setting system time from the hardware clock (UTC):  "                         echo -n "Setting system time from the hardware clock (UTC):  "
    /sbin/hwclock $CLOCK_OPT --utc --hctosys                                               /sbin/hwclock $CLOCK_OPT --utc --hctosys
  fi                                                                                     fi
  date                                                                                   date
fi                                                                                     fi

michaelk · 03-22-2022, 11:49 AM

Code:

-- Shows the correct date and time (CDT)
# hwclock --show
2022-03-20 14:33:02.293381-05:00

-- Off by 5 hrs
# date
Sun Mar 20 09:34:15 CDT 2022

# cat /etc/adjtime
0.000000 1647804661 0.000000
1647804661
LOCAL

The howclock --show always displays local time regardless if you keep the hardware clock set to UTC. The output of the date command shows CDT which appears to be the correct timezone.

The LOCAL in your /etc/adjtime configures the OS to use local time for your hardware clock. If the clock is actually set to UTC and the OS thinks its local time the system time will be off the UTC offset i.e. 5 hours.

random_guy · 03-22-2022, 01:24 PM

@kjhambrick thanks for the response. I too was looking at this script yesterday, here's what I see on my system.

$ grep " : rtc" /proc/ioports
0000-0000 : rtc0

$ [ /etc/adjtime -nt /etc/hardwareclock ] && echo "nt" || echo "not nt"
nt

$ cat /etc/adjtime
0.000000 1647955039 0.000000
1647955039
LOCAL

So, the script should be make it down to the IF condition below and
should print "Setting system time from the hardware clock (localtime): "

Just curioius, should the line after the IF condition be:
/sbin/hwclock $CLOCK_OPT --hctosys
OR
/sbin/hwclock $CLOCK_OPT --localtime --hctosys

Perhaps the assumption is because /etc/adjtime exists, the --localtime argument is redundant.

if grep -q "^LOCAL" /etc/adjtime ; then
echo -n "Setting system time from the hardware clock (localtime): "
else
echo -n "Setting system time from the hardware clock (UTC): "
fi
/sbin/hwclock $CLOCK_OPT --hctosys
elif grep -wq "^localtime" /etc/hardwareclock 2> /dev/null ; then
....

fi

kjhambrick · 03-22-2022, 02:20 PM

YW random_guy (

but I don't feel very helpful here

)

I am interested because I've got two Customers who do not connect their Servers to the internet.

I am still digging ...

-- kjh

`man hwclock` has an interesting 'newish' section:

Code:

# man hwclock
<<snip>>
       --systz
           This is an alternate to the --hctosys function that does not read the Hardware Clock
           nor set the System Clock; consequently there is not any drift correction. It is
           intended to be used in a startup script on systems with kernels above version 2.6
           where you know the System Clock has been set from the Hardware Clock by the kernel
           during boot.

           It does the following things that are detailed above in the --hctosys function:

           o   Corrects the System Clock timescale to UTC as needed. Only instead of
               accomplishing this by setting the System Clock, hwclock simply informs the kernel
               and it handles the change.

           o   Sets the kernel's NTP '11 minute mode' timescale.

           o   Sets the kernel's timezone.

       The first two are only available on the first call of settimeofday(2) after boot.
       Consequently this option only makes sense when used in a startup script. If the Hardware
       Clocks timescale configuration is changed then a reboot would be required to inform the
       kernel.

<<snip>>

Not sure it's applicable but there it is ...

random_guy · 03-24-2022, 10:23 AM

I got things working. Perhaps this will help someone else who runs into this situation.

Summary:
1. Set Hardware clock to UTC
2. Set Hardware clock Timezone to UTC
3. Set Hardware clock to desired Timezone (US/Central, in my case)
4. Sync Hardware clock to System clock

Step-by-Step:
1. Change Hardware Clock to UTC time
# hwclock --utc --set --date='2022-03-24 01:30'

2. Change timezone to UTC
# timeconfig (Answer Yes, to Hardware Clock set to UTC, then scroll and select UTC for Timezone).
# ls -l /etc/localtime
# lrwxrwxrwx 1 root root 30 Mar 24 2022 /etc/localtime -> /usr/share/zoneinfo/UTC
-- Confirm changes by running, hwclock. There should *not* be any timezone offset i.e. it should be UTC time-0 hours instead of UTC-5 (US/Central).

3. Change timezone to local timezone
# timeconfig ( Answer Yes, to Hardware Clock set to UTC, then select US/Central)
# ls -l /etc/localtime
# lrwxrwxrwx 1 root root 30 Mar 24 2022 /etc/localtime -> /usr/share/zoneinfo/US/Central

4. Sync Hardware clock to System clock
# hwclock --hctosys
# shutdown -r now

I expect this would probably work for other distros, if they provide a helper script similar to Slackwares timeconfig script.