A Murder of Crows

I few people have asked me about how to create a basic NAS based on RedHat / CentOS linux for use with ESX server. In this post, I am going to attempt to walk you through the basics of setting up a linux NFS server, and how to administer it.

Install CentOS

Download the CentOS ISO from http://www.centos.org/. Burn and put the CD in the drive and boot the computer. Just press <Enter> at the splash screen. CentOS will then ask if you want to test the CD Media. I usually skip the test.

Now you should be presented with the graphical installer. Follow the on screen instructions, and specify you language and keyboard type. Now you will be presented with the partitioning screen. Be default, CentOS likes to take over the entire disk. This is fine in most cases, but if you have a very large disk (say, the aggregate disk presented by a hardware raid controller). For our example, check the ‘Review and modify partitioning layout’, then click next.

We can see that CentOS decided to take over the entire disk, we are going to change that. Click on  the ‘LogVol00′ line and select edit. This will bring up the LVM volume editing, we only want to edit the LogVol00, so select it and press edit.

Now we are presented with the a screen that allows us to change the size of the root (/) partition. Change the size to 10000 (MB) and select OK.

Select OK again, and then next to continue the installation. Now we will see the boot loader configuration step. Just accept the defaults and select ‘Next’.

This screen allows us to configure the network. Configure the host name and network parameters as you wish, and select next. You will always be able to change them later.

Now select the timezone, and select next.

Set the root password, and select next. Now you will be presented with the software selection screen. Make sure ‘Server’ and ‘Desktop – Gnome’ is selected. ‘Desktop – Gnome’ is not necessary for CentOS to function as a NFS server for ESX, but it makes it easier to get around.

Select  ‘Next’ and your install will get started, you now get to watch the propaganda screens while you wait for your OS to be installed.

Configuring CentOS

After the system boots for the first time, there are a few things we need to do. First, CentOS will walk you through a setup wizard that will allow you to configure some settings. It is important that we set a couple of things up.

Disable the Firewall

Disable SELinux

Now you can finish the rest of the steps. It is wise to create a user account for yourself to log in as. At the end of the wizard, and one reboot later, you should see a log in prompt. Go ahead and log in with the user you create during the install process. You will be presented with a Desktop. The first thing you need to do is launch a terminal.

We will be using the terminal for the remainder of this howto.

Open up a terminal by clicking on ‘Applications->Accessories->Terminal’ and type:
<code>su -</code>
This will prompt you for the root password

Finishing the Disk partitioning.

Now, in this howto, I have configured a CentOS box with a 50GB hard drive, I would recommend the following partition layout for any size disk:

10 GB for Root (/)
4 GB for swap
70% of the remaining space for exports (the NFS word for Share)
the rest of the space will remain for a snapshot reserve.

Now a quick explanation of how linux handles mounts (or drives for the windows people). Every hard disk is “Mounted” under a directory under the root (/). So we are going to mount our primary data drive under /export.

From the terminal we are going to create a mount directory, create a logical volume called ‘esxnas1′ that is 20000MB, format the drive, then mount the drive

[root@centos ~]# mkdir /export
[root@centos ~]# mkdir /export/esxnas1
[root@centos ~]# lvcreate -L20000 -nesxnas1 VolGroup00
Logical volume "esxnas1" created
[root@centos ~]# mke2fs -j -m 0 -b 4096 /dev/VolGroup00/esxnas1
[root@centos ~]# mount /dev/VolGroup00/esxnas1 /export/esxnas1


To make the mount permanent, we need to add the following line to /etc/fstab:

/dev/VolGroup00/export /export/esxnas1 ext3 defaults 0 0

HINT: You can edit files by typing ‘nano <filename’, just type <CTRL>-X to save and quit

Configuring NFS

Now we can configure NFS, the first thing we need to do is edit the /etc/exports file by typing ‘nano /etc/exports’ and add the following:


/export/esxnas1 192.168.0.0/255.255.0.0(rw,no_root_squash)

The above will create the export, now we need to start the nfs server by typing the following:

[root@centos ~]# chkconfig --level 345 nfs on
[root@centos ~]# service nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: [ OK ]
Starting NFS daemon: [ OK ]
Starting NFS mountd: [ OK ]
[root@centos ~]# exportfs


Configure ESX to connect to your new NFS server

• Fire up you VMware Infrastructure Client and connect to your ESX server, or virtual center server.
• Click on the ESX server you want to connect, and click on the configuration tab.
• Click on the storage link
• Click on the ‘Add Storage…’ link
• Select ‘Network File System’ and click next.
• Enter in the IP address of your server, the path of the folder you exported (/export/esxnas1 in our example) and give it a name

NOTE: Keep in mind that the Datastore Name needs to be the same on all ESX servers you connect to the NFS server for vMotion and HA to work.