I have a dream: au automatic application start from a naked machine
System administration as we have known it for the past 40 years is a dying profession. What is going to arise in its place is a system
engineering task, which will involve much less heavy lifting.
In my world view, the data center will be run like this:
- You start with a data center that has power, HVAC, network and rack space. These should be built by contractors who specialize in this kind of work. The specs might be written by a sysadmin with input from facilities and networking and the database groups.
- You setup a dhcpd, PXE, and image load host somewhere, accessible all over the data center.
- You get a pile of computers
- Here is where it gets interesting....
- When it is time to install a new computer, skip the next step
- When a computer breaks, a data center technician removes the computer from the rack and puts it on a pile of known bad computers
- The technician gets a new computer, with no image on it at all and puts it in the rack.
- The technician gets the MAC (Ethernet) address and enters it and the matching IP address in to the DHCP database used by the dhcpd
- The technician enters the IP address into the PXE database along with the version of the OS it is supposed to load, along with
whatever kickstart file it should run
- The technician turns on the computer
- The computer goes through the POST, discovers that there is no OS on the disk drive nor on the floppy drive nor on the CD, so it boots from PXE
- Part of the PXE process is to get an IP address from dhcpd, which it does
- PXE loads a little kernel using TFTP
- The little kernel loads the main kernel using the kickstart file.
- The kickstart file causes whatever components are needed for the application(s) and their support to get installed.
- AS special firstboot script runs which looks at the machine's IP address, consults a (small) database that maps IP addresses to application configurations, and then loads the specific application configuration files.
example:If your production IP space uses class C RFC 1918 IP addresses, 192.168.0.0, then you may have up to 254 configurations with up to 254 hosts per configuration, without using a special subnet mask. With a special subnet mask, you may have more configurations and fewer computers or vice versa. So, for example, the machine 192.168.3.14 is the 13th computer in configuration 2.
- If a reboot is required at this point, it will be done.
- The application start up script (in /etc/init.d/) is run and the application starts.
- If this machine is a replacement for another
>The beauty of this scheme is that the once it is setup, the only opportunity for the technician to screw up is entering the IP address and MAC address of the machine into the dhcpd database.