Create a CentOS 5.5 EC2 AMI

Login

• Login as root to
  • Any CentOS machine OR
  • An EC2 CentOS instance from one of the public AMI like ami-2342a94a (32 bit) or ami-4d42a924 (64 bit)

Initialize and Mount a Loopback File used as a CentOS OS Image

• Create a working directory. For example,
  

  mkdir /mnt/image
  cd /mnt/image
  

• Create a 1G file
  

  dd if=/dev/zero of=my-image.fs bs=1M count=1024
  

• Create an ext3 file system on the new file
  

  mke2fs -F -j my-image.fs
  

• Mount the new file system
  

  mkdir /mnt/ec2-fs
  mount -o loop /mnt/image/my-image.fs /mnt/ec2-fs
  

Install the CentOS on the Loopback file

• Create the minimum device
  

  mkdir /mnt/ec2-fs/dev
  /sbin/MAKEDEV -d /mnt/ec2-fs/dev/ -x console
  /sbin/MAKEDEV -d /mnt/ec2-fs/dev/ -x null
  /sbin/MAKEDEV -d /mnt/ec2-fs/dev/ -x zero
  

• Create device mapping fstab
  

  mkdir /mnt/ec2-fs/etc
  vi /mnt/ec2-fs/etc/fstab
  

  For 32 BIT OS, use

  /dev/sda1  /         ext3    defaults        1 1
  none       /dev/pts  devpts  gid=5,mode=620  0 0
  none       /dev/shm  tmpfs   defaults        0 0
  none       /proc     proc    defaults        0 0
  none       /sys      sysfs   defaults        0 0
  /dev/sda2  /mnt      ext3    defaults        0 0
  /dev/sda3  swap      swap    defaults        0 0
  

  For 64 BIT OS, use

  /dev/sda1       /      ext3   defaults  1  1
  /dev/sdb        /mnt   ext3   defaults  0  0
  none            /proc  proc   defaults  0  0
  none            /sys   sysfs  defaults  0  0
  

• Mount Proc file system
  

  mkdir /mnt/ec2-fs/proc
  mount -t proc none /mnt/ec2-fs/proc
  

• Create YUM configuration file (For CentOS 5.5 32 bit)
  

  vi /mnt/image/yum-xen.conf
  

  [main]
  cachedir=/var/cache/yum
  debuglevel=2
  logfile=/var/log/yum.log
  exclude=*-debuginfo
  gpgcheck=0
  obsoletes=1
  pkgpolicy=newest
  distroverpkg=redhat-release
  tolerant=1
  exactarch=1
  reposdir=/dev/null
  metadata_expire=1800
  [base]
  name=CentOS-5.5 - Base
  baseurl=http://mirror.centos.org/centos/5.5/os/i386/
  gpgcheck=1
  gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
  priority=1
  protect=1
  #released updates
  [update]
  name=CentOS-5.5 - Updates
  baseurl=http://mirror.centos.org/centos/5.5/updates/i386/
  gpgcheck=1
  gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
  priority=1
  protect=1
  #packages used/produced in the build but not released
  [addons]
  name=CentOS-5.5 - Addons
  baseurl=http://mirror.centos.org/centos/5.5/addons/i386/
  gpgcheck=1
  gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
  priority=1
  [extras]
  name=CentOS 5.5 Extras $releasever - $basearch
  baseurl=http://mirror.centos.org/centos/5.5/extras/i386/
  enabled=1
  

• Install the OS
  

  yum -c /mnt/image/yum-xen.conf --installroot=/mnt/ec2-fs -y groupinstall Core
  

• Install curl
  

  yum -c /mnt/image/yum-xen.conf --installroot=/mnt/ec2-fs install curl
  

Configure the CentOS Image

• Create and edit /mnt/ec2-fs/etc/sysconfig/network-scripts/ifcfg-eth0
  

  DEVICE=eth0
  BOOTPROTO=dhcp
  ONBOOT=yes
  TYPE=Ethernet
  USERCTL=yes
  PEERDNS=yes
  IPV6INIT=no
  

• Create and edit /mnt/ec2-fs/etc/sysconfig/network
  

  NETWORKING=yes
  

• Create and edit resolv.conf
  

  search compute-1.internal
  nameserver 172.16.0.23
  

• Configure /mnt/ec2-fs/etc/ssh, run
  

  echo "UseDNS  no" >> /mnt/ec2-fs/etc/ssh/sshd_config
  echo "PermitRootLogin without-password" >> /mnt/ec2-fs/etc/ssh/sshd_config
  

• Comment out /mnt/ec2-fs/etc/inittab the following in
  

  #2:2345:respawn:/sbin/mingetty tty2
  #3:2345:respawn:/sbin/mingetty tty3
  #4:2345:respawn:/sbin/mingetty tty4
  #5:2345:respawn:/sbin/mingetty tty5
  #6:2345:respawn:/sbin/mingetty tty6
  

• Create and edit /mnt/ec2-fs/etc/ld.so.conf.d/libc6-xen.conf
  

  hwcap 0 nosegneg
  

• Add Custom Kernel module
  

  cd /mnt/ec2-fs/lib/modules
  mkdir 2.6.16-ec2
  cd 2.6.16-ec2
  wget http://s3.amazonaws.com/ec2-downloads/modules-2.6.16-ec2.tgz
  gunzip modules-2.6.16-ec2.tgz
  tar -xvf modules-2.6.16-ec2.tar
  rm modules-2.6.16-ec2.tar
  

  chroot /mnt/ec2-fs /bin/sh
  /sbin/depmod -ae 2.6.16-ec2
  exit
  

SSH Configuration

• Retrieve the SSH key when an EC2 Instance Launch /mnt/ec2-fs/usr/local/sbin/get-sshkey.sh
  

  #!/bin/sh
  if [ ! -d /root/.ssh ] ;
  then mkdir -p /root/.ssh
  chmod 700 /root/.ssh
  fi
  # Fetch public key using HTTP
  /usr/bin/curl -f http://169.254.169.254/latest/meta-data/public-keys/0/openssh-key > /tmp/my-key
  if [ $? -eq 0 ] ;
  then
  cat /tmp/my-key >> /root/.ssh/authorized_keys
  chmod 600 /root/.ssh/authorized_keys
  rm -f /tmp/my-key
  fi
  

  chmod u+x /mnt/ec2-fs/usr/local/sbin/get-sshkey.sh
  echo "/usr/local/sbin/get-sshkey.sh" >> /mnt/ec2-fs/etc/rc.local
  

• Configure system start up level for SSH Service
  

  chroot /mnt/ec2-fs /bin/sh
  chkconfig --level 345 sshd on
  exit
  

Cleanup

• Cleanup the installation
  

  yum -c /mnt/image/yum-xen.conf --installroot=/mnt/ec2-fs clean all
  

• Unmount the file systems
  

  cd /mnt
  umount /mnt/ec2-fs/proc
  umount -d /mnt/ec2-fs
  

Undo mistake

mount -o loop /mnt/image/my-image.fs /mnt/ec2-fs
mount -t proc none /mnt/ec2-fs/proc

... make any changes ...

cd /mnt
umount /mnt/ec2-fs/proc
umount -d /mnt/ec2-fs

Create the EC2 CentOS 5.5 AMI

We assume the AMI tools are installed according to the previous instructions

• Bundle the EC2 AMI CentOS 5.5 Image
  

  ec2-bundle-image -i /mnt/image/my-image.fs -c ~/.ec2/cert-aws.pem \
  -k ~/.ec2/pk-aws.pem -u 1111-2222-333
  

  Replace with your proper key/certicate and AWS account number

• Upload the AMI image to S3
  

  ec2-upload-bundle -b your_own_company_name.my-image -m /tmp/my-image.fs.manifest.xml \
  -a access-key-id -s secret-access-key
  

  Replace with the proper id/secret-key & company name

• Register the EC2 AMI
  

  ec2-register your_own_company_name.my-image/my-image.fs.manifest.xml -n centos_image