Creating a RAID device on Amazon AWS Elastic

Following procedure is for creating a software (OS managed) RAID disk devices.
EBS (Amazon web services elastic block storage) does not provide any RAID abilities by itself.
But you can use Linux SW raid option to increase either speed or device redundancy.
This tutorial will show you how.

First install RAID management tool on target EC2 instances

For Debian based (Debian, Ubuntu) execute: 
apt-get install mdadm
For Red Hat based (RHEL, Oracle linux, CentOS) execute:
yum install mdadm
For Gentoo execute:
emerge mdadm

Now prepare the EBS devices.

Create desired EBS volume
Attach new EBS volumes to EC2 instance and write down the device name (for example xvdf and xvdg)

Now you can create the RAID device from them.

Set up RAID 0 on this EBS instance with the following command:
  mdadm --create --verbose --auto=yes /dev/md0 --chunk=256 --level=0 --raid-devices=2 /dev/xvdf /dev/xvdg
   blockdev --setra 65536 /dev/md0

Now verify that the raid device /dev/md0 exists
cat /proc/mdstat

Next step is to add devices to the mdadm.conf file (main sw raid configuration file)
   echo DEVICE /dev/xvdf /dev/xvdg | sudo tee /etc/mdadm/mdadm.conf
 
Add the other device info about /dev/md0 to the mdadm.conf file so that it comes back on reboot
   mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf

Filesystem

One RAID is set up , you can create a file-system on it, we usually propose XFS, but you can use any file system (ext3/4, zfs or reiserfs)
  
To create XFS file system, you will need to install support for it first.
For Debian based (Debian, Ubuntu) execute: 
apt-get install xfsprogs
For Red Hat based (RHEL, CentOS) execute:
yum install xfsprogs
For Oracle Linux:
Log in to ULN, and subscribe your system to the ol6_x86_64_latest channel.
Then run:
yum install xfsprogs xfsdump 
For Gentoo execute:
emerge xfsprogs 

Once installed, execute
mkfs.xfs -f /dev/md0
to create an actual filesystem on your new RAID device.
  
Now you can mount the file system
   mkdir /MOUNTPOINT (for example /raid)
   mount /dev/md0 /MOUNTPOINT (for example /raid)
 
Verify the volume exists and the size you expected
df -h 
 
Edit /etc/fstab to make sure mount point comes back on reboot
/dev/md0 /raid xfs noatime,noexec,nodiratime 0 0

You have the new RAID based partition in your system.
Same procedure will work on both public EC2 cloud and VPC.

Provided by:Forthscale systems, cloud experts

working and tested USB install procedure for RH 6 based distributions (RHEL 6.x, CentOS 6.x, Oracle Linux 6.x and others)

We needed to install CentOS 6.4 machines with USB and got into absolute madness. All RHEL cones have no working procedure and workarounds consisted of using FAT32 partition with 3rd party tools (problematic with install ISO files greater than 4GB) or multiple partitions and remounts. Until we found a very simple solution that did not work as well and fixed it.

To create the USB You will need:

• Red hat based distribution to create the USB (in our case CentOS-6.4-x86_64-bin-DVD1.iso). 
• Actual CD iso image 
• Fedora livecd-iso-to-disk script

Steps are very simple:
Insert the USB stick to the port.
You need to find out the device name (for ex. /dev/sdb1 )
On systems with auto-mount just run df -h or plug it in and run dmesg | tail -20

Install livecd tools:
yum install livecd-tools

Make sure it is bootable  (for ex. /dev/sdb1, via editing it`s parent - sdb ):
/sbin/parted /dev/sdb
(parted) toggle 1 boot
(parted) quit

Format it with ext3 (does not support ext4)
mkfs.ext3 /dev/sdb1

Prepare the USB (for example using CentOS 6.4):
livecd-iso-to-disk --reset-mbr CentOS-6.4-x86_64-bin-DVD1.iso /dev/sdb1

Your USB is ready, it will boot but fail to install since it is missing install root, so we need to fix it.
Edit exlinux.conf, you will see something similar to:
append initrd=initrd.img stage2=hd:UUID=791fc126-638c-4f28-8837-f3c2eae31e57:/images/install.img repo=hd:UUID=791fc126-638c-4f28-8837-f3c2eae31e57:/

what is mising is directive "root=" so you need to switch the line to something similar to: 
append initrd=initrd.img root=UUID=2cd71b0d-09a0-47b6-97ef-02c3fa90e9d3 repo=hd:UUID=2cd71b0d-09a0-47b6-97ef-02c3fa90e9d3:/

save the file and boot fro USB. It will install your OS.

Provided by: Forthscale systems, cloud experts

Setting up updates with public yum server for Oracle Enterprise Linux

Oracle provides a free and public yum server to update it`s Enterprise Linux distribution.
It is easy to set-up and it supports versions 4, 5 and 6.

To set up public repositories for different versions, download configuration file (for ex. with wget)

In Oracle Enterprise Linux 6.x

# cd /etc/yum.repos.d
# wget https://public-yum.oracle.com/public-yum-ol6.repo

In Oracle Enterprise Linux 5.x
# cd /etc/yum.repos.d
# wget https://public-yum.oracle.com/public-yum-el5.repo



In Oracle Enterprise Linux 4, Update 6 or Newer
# cd /etc/yum.repos.d
# if you have old repo file then:
# mv Oracle-Base.repo Oracle-Base.repo.disabled
# wget https://public-yum.oracle.com/public-yum-el4.repo

You can verify new configuration with:
#  yum list

And execute update with :

# yum update

Provided by: Forthscale systems, scalable infrastructure experts