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Howto createcustomcentosam iforebsstorage-200913-1043-13
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Step by Step Guide to Create a Custom Amazon AMI for (Instance or EBS Based). This is how I have built AMI for customers using Amazon Web Services.

Step by Step Guide to Create a Custom Amazon AMI for (Instance or EBS Based). This is how I have built AMI for customers using Amazon Web Services.

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  • 1. How to Create Custom CentOS AMI for EBS Storage Author : Kanwar Batra Audience : System Administrators, Architects, Technical Managers. Relevance : This document outlines the Amazon AMI creation and Conversion to a EBS Boot device. Prepare a Linux Host Install a CentOS machine on a Physical , Virtual infrastructure. ( This document is based on the CentOS 6.4 Minimal Install cd) Update the Yum repository ( Run command as )root sudo yum -y update ; sudo yum install -y MAKEDEV Setup the environment with ec2 credentials . Change your root (The file start with a Dot).bashrc file with attached Source the root bashrc #source ~/.bashrc Install Linux Packages below # yum -y install e2fsprogs ruby java-1.6.0-openjdk unzip wget Download your x509 Private Key and Certificate from the AWS Security Credentials. If none exist create new Private Key format : pk-<Alpha Numeric String>.pem x509 Cert format : cert-<alpha Numeric string>.pem Copy the above certificates to /opt/ec2/certificates cp -rf pk<Alpha Numeric String>.pem /opt/ec2/certificates/ec2-pk.pem cp -rf cert<Alpha Numeric String>.pem /opt/ec2/certificates/ec2-cert.pem Download the EC2 api and Ami command line utilities wget http://s3.amazonaws.com/ec2-downloads/ec2-ami-tools.zip wget http://s3.amazonaws.com/ec2-downloads/ec2-api-tools.zip Unzip the downloaded tools to /opt/ec2/tools. Combine both tools in same directory ( Say no to any existing files). cp "ec2-api-tools.zip" /opt/ec2/tools-rp cp "ec2-ami-tools.zip" /opt/ec2/tools-rp EC2 api and ami utilities are java base. Set JAVA_HOME if not set export JAVA_HOME=/usr/lib/jvm/jre-1.6.0-openjdk.x86_64 (Eg For Open JDK) export JAVA_HOME=/usr/java/jdk1.7.0_25 ( for Oracle/Sun Java) Verify Java Version java -version Check the ec2 regions that would determine location for image [root@nf_lnx_ami bin]# ./ec2-describe-region REGION eu-west-1 ec2.eu-west-1.amazonaws.com REGION sa-east-1 ec2.sa-east-1.amazonaws.com REGION us-east-1 ec2.us-east-1.amazonaws.com REGION ap-northeast-1 ec2.ap-northeast-1.amazonaws.com REGION us-west-2 ec2.us-west-2.amazonaws.com REGION us-west-1 ec2.us-west-1.amazonaws.com REGION ap-southeast-1 ec2.ap-southeast-1.amazonaws.com REGION ap-southeast-2 ec2.ap-southeast-2.amazonaws.com
  • 2. Verify the availability Zones that you can connect ec2-describe-availability-zones --region us-east-1 ( The output should look as below) AVAILABILITYZONE us-east-1a available us-east-1 AVAILABILITYZONE us-east-1b available us-east-1 AVAILABILITYZONE us-east-1c available us-east-1 AVAILABILITYZONE us-east-1d available us-east-1 Steps to Build the AMI Installing the Operating System To build the EBS Based AMI first we will create a Instance Base AMI and then after upload will convert it to EBS Storage AMI. Start the image creation in an empty directory. (eg /opt/ec2/images) Create an empty file using dd dd if=/dev/zero of=/opt/ec2/images/centos-6.4-Minimal-x86_64-base.img bs=1M count=10240 Initialize the image file with a filesystem `mkfs.ext4 -F -j /opt/ec2/images/centos-6.4-Minimal-x86_64-base.img Create an empty directory and mount the initialized image file as a loopback mount -o loop /opt/ec2/images/centos-6.4-Minimal-x86_64-base.img /mnt/ec2-image/ Verify the image mounted using the mount command mount df -h | grep image /opt/ec2/images/centos-6.4-Minimal-x86_64-base.img 9.9G 151M 9.2G 2% /mnt/ec2-image Setup directories in the image before installing the Operating system mkdir -p /mnt/ec2-image/{dev,etc,proc,sys} mkdir -p /mnt/ec2-image/var/{cache,log,lock,lib/rpm} Create minimum required devices on /dev in the image location using MAKEDEV ignore any File exists warnings . /sbin/MAKEDEV -d /mnt/ec2-image/dev -x console /sbin/MAKEDEV -d /mnt/ec2-image/dev -x null /sbin/MAKEDEV -d /mnt/ec2-image/dev -x zero /sbin/MAKEDEV -d /mnt/ec2-image/dev -x urandom Mount the current running O/S dev,ptr into the image's root filesystem built above. mount -o bind /dev /mnt/ec2-image/dev
  • 3. mount -o bind /dev/pts /mnt/ec2-image/dev/pts mount -o bind /dev/shm /mnt/ec2-image/dev/shm mount -o bind /proc /mnt/ec2-image/proc mount -o bind /sys /mnt/ec2-image/sys Verify the mount for the new root fs is visible using Mount command. mount | grep image /dev on /mnt/ec2-image/dev type none (rw,bind) /dev/pts on /mnt/ec2-image/dev/pts type none (rw,bind) /dev/shm on /mnt/ec2-image/dev/shm type none (rw,bind) /proc on /mnt/ec2-image/proc type none (rw,bind) /sys on /mnt/ec2-image/sys type none (rw,bind) Add a yum config of the centos image in /opt/ec2/yum directory as attached Install the Base packages and O/S supporting utilities using the above created yum-xen.conf yum -c /opt/ec2/yum/yum-xen.conf --installroot=/mnt/ec2-image -y groupinstall Base yum -c /opt/ec2/yum/yum-xen.conf --installroot=/mnt/ec2-image -y install *openssh* dhclient yum -c /opt/ec2/yum/yum-xen.conf --installroot=/mnt/ec2-image -y install grub yum -c /opt/ec2/yum/yum-xen.conf --installroot=/mnt/ec2-image -y install selinux-policy selinux-policy-targeted yum -c /opt/ec2/yum/yum-xen.conf --installroot=/mnt/ec2-image -y install vi *openjdk* Configure Network for Image Update the files in the Image root file system vi /mnt/ec2-image/etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE=eth0 BOOTPROTO=dhcp ONBOOT=yes TYPE=Ethernet USERCTL=yes PEERDNS=yes IPV6INIT=no vi /mnt/ec2-image/etc/sysconfig/network NETWORKING=yes HOSTNAME=localhost.localdomain Setup network to start on boot /usr/sbin/chroot /mnt/ec2-image /sbin/chkconfig --level 2345 network on Selinux configuration Relabel Selinux label in the image touch /mnt/ec2-image/.autorelabel
  • 4. Update /etc/sysconfig/selinux SELINUX=disabled Storage and File system setup create a base fstab on the image . Please make sure the first device is xvde as it is the Amazon xen default root device. cat > /opt/ec2/image/etc/fstab <<EOF /dev/xvde1 / ext4 defaults,noatime 1 1 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 EOF Configure the boot file - grub.conf in the image boot directory Create a default grub file as and then from command lineattached here $ ln -s /boot/grub/grub.conf /mnt/ec2-image/boot/grub/menu.lst $ kern=`ls /mnt/ec2-image/boot/vmlin* | awk -F / '{print $NF}'` $ ird=`ls /mnt/ec2-image/boot/initramfs*.img|awk -F/ '{print $NF}'` $ sed -ie "s/vmlinuz/$kern/" /mnt/ec2-image/boot/grub/grub.conf $ sed -ie "s/initramfs/$ird/" /mnt/ec2-image/boot/grub/grub.conf Securing Login Add the following parameters or uncomment if they exist in /etc/ssh/sshd_config for the image vi /mnt/ec2-image/etc/ssh/sshd_config PermitRootLogin without-password UseDNS no Add the validation for root user with Private Key. Script attached Register the validation script as a service and update it's run level from command line $ /bin/chmod +x /mnt/ec2-image/etc/init.d/ec2-get-ssh $ /usr/sbin/chroot /mnt/ec2-image /sbin/chkconfig --level 34 ec2-get-ssh on Cleanup before AMI Bundle creation Run the and verify the mounts bound to source have been removedattached cleanup script $ mount ( Verify no new root filesystem directories are bound to the host) AMI creation and upload (Instance Base AMI) Get the kernel information for your location. This is dependent on the EC2_URL environment variable. the following is for us-east-1 (use highlighted in our example) ec2-describe-images --owner amazon
  • 5. --region us-east-1 | grep "amazon/pv-grub-hd0" | awk '{ print $1, $2, $3, $5, $7 }' IMAGE aki-b2aa75db amazon/pv-grub-hd00_1.03-i386.gz available i386 IMAGE aki-b4aa75dd amazon/pv-grub-hd00_1.03-x86_64.gz available x86_64 IMAGE aki-b6aa75df amazon/pv-grub-hd0_1.03-i386.gz available i386 IMAGE amazon/pv-grub-hd0_1.03-x86_64.gz available x86_64aki-88aa75e1 Bundle the AMI using the following command. Make sure all the AWS environment variables are setup (Will run for a while based on image size) ec2-bundle-image --cert $EC2_CERT --privatekey $EC2_PRIVATE_KEY --image /opt/ec2/images/centos-6.4-Minimal-x86_64-base.img --prefix centos-6.4-Minimal-x86_64-base --user $AWS_ACCOUNT_NUMBER --destination /opt/ec2/ami --arch x86_64 --kernel aki-88aa75e1 The output will log message about splitting the image and create a manifest. Finally you should see (ec2-bundle-image complete.) Upload the AMI to Amazon and verify that all parts are uploaded ec2-upload-bundle --manifest /opt/ec2/ami/centos-6.4-Minimal-x86_64-base.manifest.xml --bucket $AWS_AMI_BUCKET --access-key $AWS_ACCESS_KEY_ID --secret-key $AWS_SECRET_ACCESS_KEY Register the AMI with the appropriate Kernel ID, you should get the final AMI created info as in blue below ec2-register $AWS_AMI_BUCKET/centos-6.4-Minimal-x86_64-base.manifest.xml --name "CentOS 6.4 base (x86_64)" --description "CentOS 6.4 b (x86_64) Base AMI" --architecture x86_64 --kernel aki-88aa75e1 IMAGE ami-5beea532 This completes the full AMI build and Upload for the Instance Base AMI. Converting Instance Base AMI to EBS AMI Amazon does not provide building the EBS AMI directly from their CLI. To build a EBS AMI follow the steps below Launch AWS Console and navigate to EC2 To create the instance click the "Launch Instance" button on the Dashboard. Please note instance is created in the selected Zone Zone Selected (Top Right shows the Current Selected Zone. Dropdown show all Zones)
  • 6. Create Instance use Launch Instance (using the Instance Based AMI we created ) Steps to convert to an EBS Backed AMI Login to the Instance that was launched in the previous step Create a EBS Volume by navigating to "Volumes" in the EC2 Dashboard Volume Parameters Volume Type : Provisioned IOPS(io1) Size : 20 GiB IOP's : 200 Availability Zone : <Pick from List> Snapshot : no snapshot Attach the EBS Volume to the Instance created with the Instance based AMI Steps to Attache EBS Volume Login to the instance as root fdisk -l fdisk /dev/xvdj (You should see the attached EBS from the list our's shows xvdj) Create a primary partition using following flags one in Fdisk (n - new partition, p- Primary Partition, 1 - first partition , choose 1st and last cylinder of disk, w - write) Create a filesystem on the new EBS disk mkfs.ext4 /dev/xvdj1 Create a directory to mount the new Volume mkdir /mnt/ebsvol
  • 7. Sync the root filesystem to the mounted directory rsync -avH --exclude /mnt --exclude /sys --exclude /proc --exclude /dev / /mnt/ebsvol Create the required directories and devices # mkdir -p /mnt/ebsvol/{dev,etc,proc,sys} # /sbin/MAKEDEV -v -d /mnt/ebsvol/dev -x console # /sbin/MAKEDEV -v -d /mnt/ebsvol/dev -x null # /sbin/MAKEDEV -v -d /mnt/ebsvol/dev -x zero Copy the resolv.conf to the /mnt/ebsvol/etc cat /etc/resolv.conf > /mnt/ebsvol/etc/resolv.conf Update the grub.conf in /mnt/ebsvol/boot/grub directory replace (hd0) -> (hd0,0) Sync the filesystem sync;sync;sync;sync Unmount the EBS volume umount /mnt/ebsvol Detach the EBS Volume from the instance from the AWS Console Create a Snapshot of the EBS Volume from the AWS Console Create an Image from Snapshot from the "Snapshot" in AWS Console During Instance Registration you must Select the correct KERNEL_ID for your desired Zone or the EBS AMI instance will give errors during startup. Launch an Instance with the correct KERNEL_ID and you should see a running EBS Instance. Benefits of EBS Based instances are that you can snapshot a ebs instance and is easy to recover if accidently terminated when Termination Protection is Disabled. As long as you maintain frequent snapshots. References: This tutorial was built using the following tutorials http://blog.bashton.com/2012/how-to-make-your-own-centos-6-amis/ http://www.practicalclouds.com/content/guide/ http://amazonaws.michael–martinez.com/ http://wiki.sysconfig.org.uk/display/howto/Build+your+own+Core+CentOS+5.x+AMI+for+Amazon+EC2 http://lists.centos.org/pipermail/centos/2011-January/105377.html http://www.ioncannon.net/system-administration/1205/installing-cent-os-5-5-on-ec2-with-the-cent-os -5-5-kernel/