Month: July 2014

Symptom

User is not able to “su” to another account (be it local, or LDAP based)

[admazwan_ngali@oracle~]$ su - servicesoasit
Password:
Password:
su: incorrect password

/var/log/secure will display this error log.

Jul 21 23:53:37 oracle su[22863]: pam_vas: Authentication <succeeded> for <Active Directory> 
user: <servicesoasit> account: <ServiceSOASIT@AMER.DELL.COM> service: <su-l> reason: <N/A> Access Control Identifier(NT Name):<AMERICAS\ServiceSOASIT>
Jul 21 23:53:38 oracle su[22863]: pam_unix(su-l:auth): authentication failure; 
logname=admazwan_ngali uid=2184379 euid=2184379 tty=pts/6 ruser= rhost=  user=servicesoasit

As you can see pam_vas already verified authentication is a success, but “su” still refused you to switch user.

Troubleshooting

Ensure setuid is set on /bin/su file. Not sure why it’s changed, probably it happened during OEL upgrade recently.

[root@oracle pam.d]# ll /bin/su
-rwxr-xr-x 1 root root 28336 Oct 16  2012 /bin/su

Try to “su” to another account again. Issue should be fixed.

[root@oracle pam.d]# chmod +s /bin/su
[root@oracle pam.d]# ll /bin/su
-rwsr-xr-x 1 root root 28336 Oct 16  2012 /bin/su

[admazwan_ngali@oracle ~]$ su - servicesoasit
Password:
[servicesoasit@oracle~]$

Working on some performance related issue today and user requested average CPU/Memory utilization history on previous days, so I came out with quick script to pull the data.

Tested on Oracle Enterprise Linux. Should be working fine on any RHEL based distribution. Sysstat package is required to enable sar report on your server.

#!/bin/bash

# Get Average CPU/Memory Utilization History from sysstat file in /var/log/sa/*
# Author: azwan.ngali[AT]gmail.com


for file in $(ls -la /var/log/sa/* | grep sa[0-9] | awk '{print $9}')
do
        sar -f $file | head -n 1
        printf "\n"

        # Get CPU idle average, it's pretty straight forward.

        printf "CPU average: "
        sar -u -f $file | grep Average: | awk -F " " '{sum = (100 - $8) } END { print sum "%" }'

        # Get Average Memory utilization

        # Information being displayed in sar -r command is somewhat misleading.
        # As it is merely calculated by the formula kbmemused/(kbmemused+kbmemfree) * 100
        # But actually that was not the case, in order to get memory calculation, 
        # here's the revised formula to include memory cache/buffer information into account.
        # 
        # Formula:
        # (kbmemused-kbbuffers-kbcached) / (kbmemfree + kbmemused) * 100
        # The reason behind this is Linux treats unused memory as a wasted resource and so uses as 
        # much RAM as it can to cache process/kernel information
		
        printf "Memory Average: "
        sar -r -f $file | grep Average | awk -F " " '{ sum = ($3-$5-$6)/($2+$3) * 100   } END { print sum "%" }'

        printf "\n"
done

Upon execution, it will search all sa* file in /var/log/sa and perform basic calculation to display CPU/memory average. It may be handy if you’re lazy like me.

[root@ausuovmfmtap3 sa]# ./averagesar.sh
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/01/2014
CPU average: 4.76%
Memory Average: 15.6925%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/02/2014
CPU average: 3.4%
Memory Average: 14.3805%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/03/2014
CPU average: 3.35%
Memory Average: 14.576%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/04/2014
CPU average: 3.97%
Memory Average: 17.8241%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/05/2014
CPU average: 4.44%
Memory Average: 20.4096%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/06/2014
CPU average: 4.58%
Memory Average: 20.6211%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/07/2014
CPU average: 4.77%
Memory Average: 18.3188%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/08/2014
CPU average: 3.34%
Memory Average: 14.8783%
 
Linux 2.6.18-274.el5 (ausuovmfmtap3.xx)        07/09/2014
CPU average: 3.44%
Memory Average: 15.1599%
 
[root@ausuovmfmtap3 sa]#

Toodles.