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Old 11-01-2012, 07:26 AM   #1
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Registered: Nov 2012
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Issue with hwclock

Using Kernel version "2.6.31"

When checked uptime & last reboot time(who -b)showing different time values.

uptime;who -b
17:23:51 up 2:13, 1 user, load average: 0.00, 0.00, 0.00
system boot Oct 25 17:10

Found issue the "/usr/sbin/hwclock" command
Cannot access the Hardware Clock via any known method.
Use the --debug option to see the details of our search for an access method.

/usr/sbin/hwclock --debug
hwclock from util-linux-2.13-pre7
hwclock: Open of /dev/rtc failed, errno=19: No such device.
No usable clock interface found.
Cannot access the Hardware Clock via any known method.

Showing two RTC devices
ls -la /dev/rtc*
crw------- 1 root root 10, 135 Oct 25 2012 /dev/rtc
crw------- 1 root root 253, 0 Oct 25 2012 /dev/rtc0

Also checked hwclock is getting sync with system time.(Output below) #adjtimex --print
mode: 0
offset: 0
frequency: 0
maxerror: 16000000
esterror: 16000000
status: 64
time_constant: 2
precision: 1
tolerance: 32768000
tick: 10000
raw time: 1351766268s 546197us = 1351766268.546197

When I deleted the old RTC (/dev/rtc) & add a SYMLINK as below

ln -s /dev/rtc0 /dev/rtc

The /usr/sbin/hwclock command worked & showing same time as system time.

Thu Oct 25 17:35:10 CEST 2012
Thu Oct 25 17:35:11 2012 -0.691976 seconds

It show onlt one RTC devices with major no 253 that's for /dev/rtc0

# cat /proc/devices
Character devices:
1 mem
4 /dev/vc/0
4 tty
4 ttyS
5 /dev/tty
5 /dev/console
5 /dev/ptmx
7 vcs
10 misc
13 input
98 comedi
128 ptm
136 pts
180 usb
189 usb_device
253 rtc
254 bsg

# ls -l /dev/rtc0
crw------- 1 root root 253, 0 Oct 30 17:50 /dev/rtc0

The binary /usr/sbin/hwclock is supposed to fall to /dev/rtc0 if /dev/rtc isn't working or non-functioning.

"When using Kernel version 2.6.18; uptime & last reboot time values are OK.".

I don't really understand the issue is with kernel version 2.6.31 or binary /usr/sbin/hwclock is not able to handle two RTC devices


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