Setup Lab Environment using CentOS Linux and Oracle VirtualBox

Last week I started Red Hat Server Hardening (RH413) online training from Network Nuts so thought of setting up my lab environment to exercise the quiz at the end of each unit. I decided to use the open source CentOS Linux and Oracle VirtualBox on my Dell Latitude Windows 7 laptop so it won't hurt my pocket with extra cost. As this is going to be a lab environment and we experiment and break things up so it is a good practice to have a baseline image of the operating system which we can use to create multiple identical virtual machines within few minutes when needed using Clone feature. VirtualBox also has another great feature and that is point in time snapshot. Let's check out the step by step process to build the lab environment,

Collect Centrify DirectControl Debug Log

In this post I am gonna provide you the steps to collect the debug logs that should be provided while reporting an authentication failure issue with Centrify DirectControl. If you have the paid version then you can simply send an email to with the logs files otherwise Centrify Forum is the one great stop shop for you. Make sure you run these steps before fixing the issue like restarting the system or restarting the centrifydc service.

These steps are for RHEL (Red Hat Enterprise Linux) users but other distributions should have similar steps just the directory structure might change a little bit,

Python Script: Check Ping Status and Lookup Hostname from IP List

Today I got a request to disable insecure SNMP v1 / v2c from a list of IP addresses. If you are still using SNMP v1 / v2c then it's really the time to disable the version and configure secured SNMP v3. Sometime ago I wrote a post on how to install and configure Net-SNMP v3 in Red Hat Enterprise Linux 4, you might wanna check that out as well. So, I had no idea what these servers are because I like to memorize my servers with their host name. And I didn't want to run nslookup or host or dig one by one on each IP. Also, I wanted to check whether these IP are alive / ping-able on my network or not. I could have used for loop and made one complicated command but for couple of reasons I chose not to do that,

adclient: DEBUG util.except (cims::RPC) : NetLogon::authenticate failed: Buffer Overflow

If you running DirectControl 5.0.x and have addebug enabled then you may see below authenticate failed messages pretty much every 30 seconds in your /var/log/centrifydc.log file,

adclient[12219]: DIAG  <bg:updateOS> smb.rpc.netlogon authenticate - useAuthen3=1.

adclient[12219]: DEBUG <bg:updateOS> util.except (cims::RPC) : NetLogon::authenticate failed: Buffer Overflow (reference ../smb/rpcclient/netlogon.cpp:247 rc: -2147483643)

These messages are getting logged because your computer's samAccountName (in layman's terms hostname) is greater than 15 characters long on DirectControl 5.0.x. This has been fixed in 5.1.0 and in current latest version that is 5.1.2 at the time of writing this blog post.

VMware vSphere: Design Workshop Class

It was the first day of my VMware vSphere: Design Workshop class and I was quite excited to learn the designing stuff, kind of my second step after VCP (VMware Certified Professionals) towards the vSphere Architect role. The class was taught by Patrick Fong trainer from at VMware Singapore and I find him straight forward and nice guy. It’s a slides based training class and one of the good things about that is it covers most of the topics and details, big or small, that are necessary from the VMware’s perspective but it leaves less time to discuss the real life designs and the experiences. I want to see more production designs to talk about and little less theory as VMware has done a great job on white papers, documentation and knowledge base.

Setup Net-SNMP v3 on VMware ESX 4.0

Most enterprises have central monitoring system which is used to monitor pretty much every system/network gear in the infrastructure. In this post we will configure secure user based Net-SNMP v3 Agent on VMware ESX 4.0 so these hosts can also be monitored from the same central monitoring system in a secured manner. If you want to install and configured Net-SNMP v3 on RHEL4 systems then check out my other post. You need to perform these steps as root user so login to ESX 4.0 console as root now.

Bash Script: Monitor Inode Usage for UFS in Solaris 10

A file is the smallest unit of storage in the Unix file system (UFS). In Unix and Unix-like operating systems, each file is associated with an inode (Index Node) that stores the attributes like permissions, owner, group, size, type, time stamp, and etc. of file system objects like regular file, directory, and etc. Note that an inode contains all the information about a file except its name, which is kept in a directory. The size of an inode is 128 bytes. The inode allocation in UFS is static unlike XFS or NTFS that can easily cause lack of inodes if you have lot of small files. This makes the situation critical to place inode monitoring in place and do some trend analysis to prevent downtime. So here is a bash shell script to monitor the inode usage for UFS in Solaris 10. The script can send you the email notification if the inode usage goes over 90% and also logs the data in CSV format for tracking the growth. You need to run the script from cronjobs so that it can work even if you are not in front of your server.