VMWare ESXi secret console

VMWare's ESXi is a free version and lightweight version of the VMWares ESX platform. It supports most of the key features that ESX has but comes in appliance like package which doesn't let you configure anything more than just the basic hostname/IP settings. THIS IS NOT TRUE! Infact, ESXi is built from a similar linux variant as the ESX. This is a hidden secret feature.

To reach this secret console go through the following steps.
1) Get to the ESXi console (TUI - Text User interface)
2) Press Alt - F1
3) Enter "unsupported" and hit enter (You will not see any typed)
4) Login in with your root password
5) Congratulations! you have unlocked the secret console!

With this console you can enable ssh with the following steps
1) Login with the above steps
2) Edit the /etc/inetd.conf file
3) Uncomment the SSH session and save the file
4) ps |grep inetd (to get the PID)
5) kill -HUP (to reload the inetd process)
6) Login with your favourite ssh client!

PIX Firewall operating in one arm configuration

I have been befuddled once with setting the Cisco PIX/ASA in a one arm routing configuration. To picture below explains this:



Basically when you set the ASA as a default gateway, you are unable to have to ASA forward (or route) packets in and out of the same interface. This was the case in version 6.0 of the PIX OS. However with version 7.2(1) and later it can now be done via the command "same-security-traffic permit intra-interface".

A link with the how to can be found on the cisco website

Datacenter Capacity Planning

A lot needs to be considered when planning for a datacenter. Power, cooling, UPS, generators, rack space, cost. All these come into play.

Here are a few links to some vendor calculators I came across that has helped me.

DELL

HP

Displaying 32/64 rpms installed on a Redhat system

It's been a while since I've prepared an Oracle Linux server. Today I got handed a hot potato - "An Oracle Linux server with missing Libraries". This is often the case with oracles installer - It won't install without the proper libraries. What had happened was the previous sysadmin installed the 32bit versions of the libraries and Oracle was looking for the 64bit version. However, with Redhat's default rpm -qa command it often displays only the package but doesn't tell you the architecture of the package. Here's a neat command that would display the architecture of the installed package.

rpm -qa --queryformat "%{NAME}-%{VERSION}.%{RELEASE} (%{ARCH})\n"

Give this a try the next time you install a 64bit Redhat system.

iSCSI @ Home

iSCSI or internet SCSI is a standard for running SCSI over an ip based network. For people familiar with this technology it basically enables you to mount remote disks over your existing IP infrastructure.

Today I setup a simple iSCSI mount on Linux for my local windows desktop at home over my home network. Lets start with the basic terminology and requirements.

You need a Linux box with plenty of storage space, preferably with RAID and a decent network connection - 1G acting as your SAN. This will be your iSCSI target.

Then you need a Linux or Windows desktop to act as your mount point - The iSCSI initiator.

Here are some links on the web which explains this more in detail
Setting up iSCSI in 5 mins
Enterprise iSCSI for Linux
Microsoft iSCSI iniator

Building a simple iSCSI was as simple as following those links and instructions and downloading the appropriate files.

In my quick and dirty implementation I didn't have a high performance disk setup nor a proper LVM setup to export my devices. However, the Linux Enterprise iSCSI target supports exporting files as a virtual file/block device. So I simply created an empty 10G file as my iscsi mount by using dd.

dd if=/dev/zero of=/tmp/iscsi-file bs=1M count=10240

I then exported the /tmp/iscsi-file as LUN0 in the ietd.conf file. It's as simple as that!

Setting up the Windows iSCSI initiator was as simple as eating lettuce.

Next, I'll be posting about setting up the Linux iSCSI initiator as that is a bit more complicated and may require more troubleshooting steps.

##Update
Someone recommended me to a more powerful open source tool for SAN,NAS,iSCSI.
It's called openfiler. Seems like an awesome tool!

Vsftp chroot - Unable to follow symlinks!!

Today I setup vsftp for local user ftp access. I turned on 'chroot_local_user=YES' which essentially puts the ftp user into a chroot jail. But what happens when you want to access something outside of user's home directory?

What? Symlinks don't work?!

Here's the solution I found on the net: Link

Basically you have to mount the external directory into your current directory using the --bind option. That nice link in the article tells you how to do it and how to put it in your fstab file to make it permanent after a reboot!

Happy reading!

Upgrading an Entrepreneur ASP infrastructure - PART III

VMware - The leading industry Virtualization Provider. It comes in two flavors VMWare ESX and VMWare Server (formerly GSX). The former comes at a cost and the latter FREE!

In a low cost setup Vmware server (Free version) is the best recommended solution. Although I must mention that the ESX server provides additional much wanted enterprise features such as support for Network attached SAN, iscsi, clustering and resource pooling.

VMWare is supported on many OSes, Windows, Redhat, CentOS, Ubuntu and more.

In this setup I recommend using CentOS as the base operating system as it is built from the stable Redhat Enterprise Linux source and is free!

Below are steps that should be followed to prepare for VMWare installation.

1. Prepare mirrored hardware RAID if available.
2. Partition the system as follows during OS installation:

- Boot (ext3,primary) = 100 mb
- LVM (LVM,primary) = All remaining space
- LVM name = RAID1
- SWAP = 2G (or 2 x RAM)
- TMP (/TMP) ext3 = 1G
- VAR_LOG (/var/log) ext3 = 2G
- ROOT (/) ext3 = 5G
- VAR_LIB_VMWARE (/var/lib/vmware) ext3 = 100G+
- Leave Free space or allocate all to VAR_LIB_VMWARE

In this setup there are two logical partitions Boot and LVM. Inside LVM contains additional logical partitions with the key note that VAR_LIB_VMWARE is where all the guest OS images reside. This mount point should be in it's own partition in order to prevent allocating too much space affecting the host OS.

A LVM is a Logical Volume Manager. In current releases of Linux, LVM is installed by default for partitioning. LVM allows an administrator to dynamically resize partitions much like partition magic for windows. Conventional Linux partitions suffer from the inability to resize easily. Using Fdisk often requires the system to be booted in rescue mode and risk loss of data. By using LVM, logical volumes are now grouped into a single resource pool. In this pool is a collection of logical extents, these extents are fixed in size and are usually several megabytes. This pool of extents are then allocated to each logical volume to form a partition. When more space is needed, additional free logical extents can be added to those volumes live.