Uptime -- AIX 5.2

[mohmin]

Guys,
I am running AIX 5.2 and from couple of weeks the uptime command is not showing correct info.
We have rebooted it just yesterday and many times last week, but it still shows 27 days.

Any ideas about this problem???

Moh.

 

[RMGBELGIUM]

which maintenance level are you on?

rgds,

R.

 

[mrn]

Looks like something corrupted your /etc/utmp file.



Indicators of utmp corruption
Corruption of the utmp file shows up in two ways:

The uptime and w commands show a time greater than 8000 days since the system was last booted.
Users are shown as still logged in when in fact they are not.
Both types of corruption have many causes because both AIX commands and third party applications write to the utmp file.


Problem: uptime greater than 8000 days
If record number 0 is overwritten by anyone (normally a third party program), the uptime shows up as greater than 8000 days.


Solution
To correct the invalid boot time you must reboot the system. The utmp file is recreated with each boot.

To attempt to discover who or what overwrote the first entry in the file, use the following command to create a readable version of the utmp file and look at record 0:

NOTE: The fwtmp command must first be installed. For AIX Version 4 and above, install bos.acct.

/usr/sbin/acct/fwtmp < /etc/utmp >/tmp/out
A valid entry looks something like this:

system boot 0 2 0000 0000 818538505 Sat Dec 9 13:48:25 CST 1995
Instead of the system boot entry, you will probably find an entry like:

jones pts/2 19193 7 0000 0000 818683926 Mon Dec 11 06:12:06 CST 1995
This output means that the time stamp was corrupted by whatever program jones on pts/2 used to login. A program should never overwrite the first two entries in the utmp file. You would have to talk with jones to see what he did. This is almost always caused by a third party program that is incorrectly writing to the utmp file or a corrupted file system where the data is invalid.

The following is an awk script that can be used to attempt to clean out bad entries in the /etc/utmp file. It may not clean certain types of corruption and a reboot will be required to clean up the file.

WARNING: Since the utmp file is constantly being changed, there is always the possibility that an attempt at correction (other than by rebooting) may corrupt the /etc/utmp file.

#!/usr/bin/ksh
# utmp_clean.awk
# 12/12/95
# awk script to clean out entries in the /etc/utmp file
# that have no current matching correct process in the
# process table.
# This MUST be run by the root user, either from the
# command line or
# from the root crontab entry.
#
if [ ! -s /usr/sbin/acct/fwtmp ]
then
# accounting not installed
print "Accounting must be installed first,fwtmp file does not exist"
exit
fi
#
SUM=1
NEWSUM=0
while [ "$SUM" != "$NEWSUM" ]
do
SUM=$(/usr/bin/sum /etc/utmp)
/usr/sbin/acct/fwtmp </etc/utmp >/tmp/utmp.out
ps au |awk '{print $2,$1,$7}' |grep -v USER >/tmp/ps.out
NEWSUM=$(/usr/bin/sum /etc/utmp)
# loop until the file is unchanged
# on a busy system, this may take a long time.
done
#
cat /tmp/utmp.out | awk '
# load the array
BEGIN {
counter=0
holder = ""
ss=1
while (ss == 1)
{
ss = (getline holder < "/tmp/ps.out")
if (ss == 0)
break
n=split(holder,temp)
combine=sprintf("%s %s",temp[2],temp[3])
lookup[temp[1]]=combine
}
} # end of BEGIN section
{
if ((length($4) == 1) && ($4 == 7))
{
ps_name=lookup[$5]
if (length(ps_name) > 0)
{
#found a ps table entry with same pid
# entry needs to be checked for accuracy
#only if the name and tty match, write the entry
utmp_name=sprintf("%s %s",$1,$2)
if (ps_name == utmp_name)
print $0
}
}
else # Not an entry to look at, just pass it along
{
print $0
}
}' > /tmp/utmp.tmp
/usr/sbin/acct/fwtmp -ic </tmp/utmp.tmp >/tmp/utmp.new
# Only if the /etc/utmp file is still unchanged from when
# we last looked will the file be overwritten with the
# updated copy.
# WARNING WARNING WARNING
# There is a chance that this step may corrupt the
# /etc/utmp file if a process changes it after we look
# and before we can write it.
CURRENTSUM=$(/usr/bin/sum /etc/utmp)
if [ "$CURRENTSUM" = "$SUM" ]
then
/usr/bin/cp /tmp/utmp.new /etc/utmp
print "utmp successfully updated on "$(date)
else
print "utmp was too busy on "$(date)" to update now"
print "try again later"
fi
rm /tmp/ps.out
rm /tmp/utmp.out
rm /tmp/utmp.tmp
rm /tmp/utmp.new



Mike

"A foolproof method for sculpting an elephant: first, get a huge block of marble, then you chip away everything that doesn't look like an elephant."

http://www.airport-parking-site.co.uk/

 

[mohmin]

I have 5200-04.

Moh.

 

[mrn]

Still applies; utmp corruption.

Mike

"A foolproof method for sculpting an elephant: first, get a huge block of marble, then you chip away everything that doesn't look like an elephant."

http://www.airport-parking-site.co.uk/