Interesting date/ps time mismatch - Page 2

jim mcnamara · #8 (**permalink**) 12-13-2005

All command line utilities use time() which reads the kernel's internal timestamp - it is accurate to one second, it returns a time_t value of the the elapsed seconds since the start of the epoch.

Does this affect file times as well?

Code:

date ; touch t.lis; ls -l t.lis

r0sc0 · #9 (**permalink**) 12-13-2005

Here's the output, file times are not affected.

Quote:

SHELL=/bin/bash
TERM=xterm
HISTSIZE=1000
USER=root
USERNAME=root
MAIL=/var/spool/mail/root
PATH=/usr/kerberos/sbin:/usr/kerberos/bin:/usr/lib/courier-imap/sbin:/usr/lib/courier-imap/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin
INPUTRC=/etc/inputrc
PWD=/root
LANG=en_US.UTF-8
SHLVL=1
HOME=/root
BASH_ENV=/root/.bashrc
LOGNAME=root
LESSOPEN=|/usr/bin/lesspipe.sh %s
G_BROKEN_FILENAMES=1
_=/bin/env

[root@system root]# type ps ; type date
ps is hashed (/bin/ps)
date is hashed (/bin/date)

[root@system root]# date ; date -u
Tue Dec 13 12:41:54 EST 2005
Tue Dec 13 17:41:54 UTC 2005

[root@system root]# date ; perl -e 'print time(), " ", localtime(time()), "\n"'
Tue Dec 13 12:41:54 EST 2005
1134495715 554112131110523460

[root@system root]# touch fubar ; date ; ls -l fubar
Tue Dec 13 12:41:55 EST 2005
-rw-r--r-- 1 root root 0 Dec 13 12:41 fubar

[root@system root]# { sleep 1000 & } ; ps -fp $! ; ls -l /proc/$! ; kill $!
[1] 16681
UID PID PPID C STIME TTY TIME CMD
root 16681 12733 0 12:54 pts/83 00:00:00 sleep 1000
total 0
dr-xr-xr-x 2 root root 0 Dec 13 12:44 attr
-r-------- 1 root root 0 Dec 13 12:44 auxv
-r--r--r-- 1 root root 0 Dec 13 12:44 cmdline
lrwxrwxrwx 1 root root 0 Dec 13 12:44 cwd -> /root
-r-------- 1 root root 0 Dec 13 12:44 environ
lrwxrwxrwx 1 root root 0 Dec 13 12:44 exe -> /bin/sleep
dr-x------ 2 root root 0 Dec 13 12:44 fd
-r-------- 1 root root 0 Dec 13 12:44 maps
-rw------- 1 root root 0 Dec 13 12:44 mem
-r--r--r-- 1 root root 0 Dec 13 12:44 mounts
lrwxrwxrwx 1 root root 0 Dec 13 12:44 root -> /
-r--r--r-- 1 root root 0 Dec 13 12:44 stat
-r--r--r-- 1 root root 0 Dec 13 12:44 statm
-r--r--r-- 1 root root 0 Dec 13 12:44 status
dr-xr-xr-x 3 root root 0 Dec 13 12:44 task
-r--r--r-- 1 root root 0 Dec 13 12:44 wchan
[1]+ Terminated sleep 1000

I would say that something is pretty wrong even though files are affected

This is not good!

Perderabo · #10 (**permalink**) 12-13-2005

It looks like Linux tracks the number of clock ticks (called jiffies on linux

) since the system boot. Processes are time stamped with this count. ps obtains the boottime and adds in the clock ticks to get a process' start time. Somehow that calculation is wrong in your case. Since your system was booted, you seem to have had at least 9 minutes and 38 seconds worth too many clock ticks.

How long has your system been up? Maybe the clock is just running way too fast. Are you using ntp to keep it in sync? Or do you manually reset the clock when it is off? Ideally, ntp is supposed to detect a clock that has a consistently incorrect frequency and compensate for it. Maybe your ntpd is broken. Or you might have some jiffie-wrap. Or you might have some kernel bug that corrupted your boottime variable. All I can suggest is a reboot.

r0sc0 · #11 (**permalink**) 12-13-2005

Yeah syncing with ntp doesnt seem to have any effect. My system has only been up 45 days, so to be that out of sync seems crazy in such a short time. Hopefully its not a kernel bug, but I wont rule it out. In fact its probably a good place to start searching for a fix if a reboot doesnt do it. Thanks all.

r0sc0 · #12 (**permalink**) 01-02-2006

I just wanted to let you all know that I have rebooted the server (about a week ago) and am still having the same issue.

Code:

date;ps -ef|grep date
Mon Jan  2 10:37:12 EST 2006
root     13993 13851  0 10:39 pts/38   00:00:00 grep date

bakunin · #13 (**permalink**) 01-02-2006

This is just a suggestion and i don't know really much about Linux, but:

On AIX ntp writes to the files /etc/ntp.trace and /etc/ntp.drift (yes, silly idea to put a logfile into /etc, but I'm not responsible for it), maybe your ntp writes there (or somewhere similar) too. Maybe it helps to check out these files.

bakunin

Corona688 · #14 (**permalink**) 01-02-2006

Try 'dmesg', see anything interesting?

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