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

How to disable network manager Red Hat 6 based distributions (RHEL, CentOS, Oracle Linux)

To stop Network Manger ( for example then using pacemaker cluster) execute as root:
# service NetworkManager stop
To prevent Network Manager Service from starting at boot execute as root:
# chkconfig NetworkManager off

Keep in mind that you now need to manually configure your network interfaces.

Provided by:Forthscale systems, cloud experts

How to turn off SELINUX in Red - Hat based distributions including CentOS, Oracle Linux and Fedora?

To check  if SELinux is running execute following command:
# getenforce

To disable it, execute the following command:
# setenforce Permissive

This will put selinux in a passive (allow all) mode and last until the machine is rebooted.
 To permanently disable it, change SELINUX= line in: /etc/sysconfig/selinux.


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

Making a service autostart on Ubuntu, Debian, Oralce Linux, CentOs and Red Hat (Fedora and RHEL)

For RedHat based distributions (CentOS, Oracle Linux, Fedora) execute (as root):

chkconfig servicename on


For Debian based distributions (Ubuntu) execute (as root):

update-rc.d servicename defaults

Provided by: Forthscale systems, Linux support team

Fixing libdbus in 64 bit RPM based linux (Centos, SL, Fedora)

Issue affects Firefox, Thunderbird, gEdit etc.
You will see an error:

error while loading shared libraries: libdbus-1.so.3: cannot open shared object file: No such file or directory

most likly you have a 32 bit version of dbus libraries installed.
To fix that you need to install 64 version as well:

yum install dbus-libs.x86_64

Provided by: ForthScale systems, Cloud experts

Instalation of Nomachine NX server or VNC server on Centos 5

Both tools are great to enable external GUI remote access on Linux.

To install NX Free server:
Note. Installation of NX Server requires installation of all three packages: client, node and server due to tools and libraries dependencies.
Download the packages from Nomachine:
wget http://64.34.161.181/download/3.5.0/Linux/nxclient-3.5.0-7.x86_64.rpm
wget http://64.34.161.181/download/3.5.0/Linux/nxnode-3.5.0-9.x86_64.rpm
wget http://64.34.161.181/download/3.5.0/Linux/FE/nxserver-3.5.0-11.x86_64.rpm

Install the packages:
rpm -i nxclient-3.5.0-7.x86_64.rpm
rpm -i nxnode-3.5.0-9.x86_64.rpm
rpm -i nxserver-3.5.0-11.x86_64.rpm

VNC server installation:

yum install vnc-server
yum install xorg* (you need to install those for VNC fonts)

Provided by: ForthScale systems, Cloud experts

Adding KDE Environment to Centos 5

List installation packs on your CentOS 5 machine:
yum grouplist

Install KDE
yum groupinstall "KDE (K Desktop Environment)"

Now you might want to enable GUI remote access with either:
VNC server or Nomachine NX.

Provided by: Forthscale systems, Cloud experts

List open ports and listening services in Linux

To list open network ports (sockets) and the processes that run them on any Linux distribution use netstat. You might need to install it via yum / apt-get.
Syntax:
netstat -lnptu

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Provided by: SiQ systems, Cloud experts

Upgrading PHP in CentOS 5

CentOS 5.x comes with PHP 5.1, this version is outdated and you probably would want to upgrade it. I used Atomic repository.

You can add it by running following command:

wget -q -O - http://www.atomicorp.com/installers/atomic.sh | sh

Now you can update PHP:

yum update php

yum update php-mcrypt

(you might also need to update mysql)

Verify version of running PHP:

php -v

And that all modules working as order:

php -m

Restart Apache, you are all set.

Provided by:SiQ systems, Cloud experts

Mounting S3 bucket as a file system on Linux (Ubuntu)

In order to mount S3 bucket on Linux you need to install ssh file system (FUSE) libraries first.

Install: aptitude install build-essential libcurl4-openssl-dev libxml2-dev libfuse-dev comerr-dev libfuse2 libidn11-dev libkadm55 libkrb5-dev libldap2-dev libselinux1-dev libsepol1-dev pkg-config fuse-utils sshfs

Follow the instantiations in S3fs WIKI:

https://code.google.com/p/s3fs/wiki/InstallationNotes

It was using http download, not SVN.

Create a mount point for the new file system (ex. mkdir /mnt/s3)

Mount the file system:

ex.: s3fs tmpname -o use_cache=/tmp -o allow_other /mnt/s3

this mount comes with option of using a tmp as a cache for S3 content, you can clean that cache as you feel fit.

You can also add your bucket to /etc/fstab

s3fs#mybucket /mnt/s3 fuse allow_other,url=https://s3.amazonaws.com 0 0

Update for mounting S3 bucket on CentOS 5.5 and other old distros.
CentOS 5.5 comes with old FUSE version 2.7.4 as latest in it`s repository.
You need to manually compile version 2.8.4 befor you can use S3fs.

Remove old FUSE
yum remove fuse fuse* fuse-devel

Install needed libraries:
yum install gcc libstdc++-devel gcc-c++ curl curl* curl-devel libxml2 libxml2* libxml2-devel openssl-devel mailcap

Download new FUSE from the Sourceforge:
wget "https://downloads.sourceforge.net/project/fuse/fuse-2.X/2.8.4/fuse-2.8.4.tar.gz?r=&ts=1299709935&use_mirror=cdnetworks-us-1"

Untar and compile:

tar -xzvf fuse-2.8.4.tar.gz
cd fuse-2.8.4
./configure --prefix=/usr
make; make install


Configure FUSE in the system:
export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib64/pkgconfig/
ldconfig
modprobe fuse

Confirm that 2.8.4 is the version of FUSE displayed :
pkg-config --modversion fuse

Proceed with regular S3FS installation.

Have questions? Just contact us right away and we will be happy to assist