Steps for Building a Baseline Image

Our images are primarily derived from a stock distributions OS. Currently we're following the Ubuntu distribution line. The only core service required during installation is the ssh server. The partition size should be kept small to simplify the image gathering process. Due to limitations with the Frisbee tools we can only use ext2/ext3 file systems.

The major modifications that will be required are:

• Setting up serial console
  • Grub serial config (including kernel flags)
  • Getty serial config (for loggin in from the serial console, other wise it looks like it hangs)
• Setting Root user to have password less login (and dropping all other user records)
• removing unnecessary packages to minimize image size
• installing necessary omf/oml packages

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Version/Distributions specific Notes

Ubuntu 11.10

1. To configure grub/kernel messages to goto serial add/modify the following lines in /etc/default/grub and run update-grub:

   GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
   GRUB_TERMINAL=serial
   GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
   

   To configure the serial console for login create a file named /etc/init/ttyS0.conf and give it the following contents:

   # ttyS0 - getty
   #
   # This service maintains a getty on ttyS0 from the point the system is
   # started until it is shut down again.
   
   start on stopped rc or RUNLEVEL=[2345]
   stop on runlevel [!2345]
   
   respawn
   exec /sbin/getty -L 115200 ttyS0 vt102
   

   then start it with up start:

   sudo start ttyS0
   

   1. To configure root with no password edit /etc/shadow, the first line should look like:

      root:!:15363:0:99999:7:::
      

      remove the ! that follows the root. This will make the root account active and set the password to nil. Console logins for root will now not require a password.
      
      To get ssh to accept the changes we need to modify /etc/ssh/sshd_config make sure a couple of lines have specific values. They are:

      PermitRootLogin yes
      StrictModes no
      PermitEmptyPasswords yes
      UsePAM no