JumpStart and DHCP Servers (and building
x86 based servers with PXE)
Jumpstart on SPARC machines traditionally
made use of RARP, BOOTP etc to get the required information for building
over the network. This method does not work on x86 based machines, and
required that there be a boot server on every subnet.
PXE is the method used by x86 based machines
to start a non-attended network boot and is essentially a mini-DHCP
client which grabs the name of the bootserver and bootfile from a DHCP
server, and proceeds to load/run the named bootfile. So if you want
to install x86 (or x64) based machines non-interactively, you kind of
need to set up a dhcp server.
DHCP also has the advantage of being
able to traverse subnets through the use of DHCP forwarders, so the
number of Jumpstart servers required can be reduced.
However, its often a little more difficult
to initially set up, configure and manage . To accomodate the x86 based
servers, and the ability to jumpstart over multiple subnets, we have
added DHCP support to the core toolkit in a way that tries to hide all
the additional complexity.
Possible DHCP configurations.
# Local DHCP server hosted on the Jumpstart
server.
-
Remote DHCP
server.
-
Multiple remote DHCP
servers.
If no-one minds you running a DHCP server
on your JET server, then the first option is the easiest to configure
and set up. Additionally if you configure the routers as DHCP forwarders,
you can also jumpstart on any subnet that can "see" this DHCP server.
Unfortunately this scenario is possibly simplistic as its likely that
there's a real DHCP server lurking somewhere. (Although the number of
DHCP servers running within Datacentres is actually quite low, and you
can hope that if there IS a DHCP server, its only serving the desktop
based networks.)
This is where option 2 becomes useful.
If there already is an enterprise wide DHCP server, and its running
Sun's DHCP, then you're in luck! All you need to do is set up an ssh
relationship between your server and it, and JET will do the rest for
you.
Finally, there may in fact be multiple
DHCP servers, possibly one per subnet. JET allows you to specify which
subnets are served by which dhcp server.
N.B. When JET configures your DHCP server,
it ONLY replies to clients that have been specifically configured. i.e.
it won't just let ANYBODY plug into the network and given them an IP
address.
Simple Local DHCP server.
Firstly, you need to set up your DHCP
server. A script called "make_dhcp" is provided in /opt/jet/Products/base_config.
You only really need to run the first "dhcpconfig" command in the file,
as if you've populated either the client's sysidcfg_default_route or
the /opt/jet/etc/defaultrouters file, JET will create the network macro
for you when you run make_client.
However, you're on your own configuring
the DHCP forwarding if you're going to be DHCP serving a bunch of non-directly
connected subnets
. If there
are subnets that the JET server is NOT directly connected to, you will
need to list them in the /opt/jet/etc/server_interfaces file with the
JET server IP address as the preferred server.
Once you've done this, you need to specify
the machine types you are going to install. Edit the variable JS_DHCP_VENDOR
in /opt/jet/etc/jumpstart.conf to add them. For x86 its i86pc, for SPARC
machines, its the output of "uname -i", with the comma changed to a
period. You can list multiple servers by space separating the values.
(Don't forget to surround the whole thing by double quotes.)
In your client template, simply specify
"dhcp" as your client_allocation_method. For x64/x8 boxes just PXE boot,
for SPARC boxes you need to type boot net:dhcp - install.
Remote DHCP server.
If your DHCP server is remote, you've
got a little more work to do. Edit the /opt/jet/etc/dhcp.conf file and
provide a name for the remote dhcp server. You then need to set up ssh
between the JET server and the DHCP server so that you can ssh in without
supplying a password.
Once you've done this, just follow the
steps above from the editting jumpstart.conf bit onwards.
(Note, you need to make sure that the
default route that the DHCP server passes to the client will allow the
client to be able to route to the JET server. This is set in the Network
Macro on the DHCP server.)
Multiple Remote DHCP servers.
Support for multiple remote DHCP servers
is a simple extension to the above. Edit the /opt/jet/etc/dhcp_servers
file and list the subnets and the servers that will be DHCPing them.
You'll need to then set up each DHCP server with ssh relationships with
the JET server as above.
If the subnet is not listed in the dhcp_servers
file, JET will revert to the configuration defined in the dhcp.conf
file.
NON-Sun, NON-ssh DHCP servers.
Jet provides a mechanism which allows
you to plug in helper scripts to support other types of DHCP server.
The /opt/jet/Utils/dhcp directory contains 3 files: checkdhcp, configdhcp
and deconfigdhcp. Each of these files calles a script of asimilar name
based on the settings in the dhcp.conf file. i.e. If the DHCP_FORMAT
was set to SUN (the default), it would call checkdhcp_SUN. If it was
remote and the method was "ssh", it would call checkdhcp_SUN_ssh.
To add support for other dhcp types and
remote communication mechanisms, you simply need to specify the new
format/type in dhcp.conf, and then create the scripts of the correct
name in the dhcp directory. (configdhcp_xx_yy does all the real work.
It reads the settings required for the client in a file called dhcp.config
in the Client directory and communicates with the DHCP server to set
them up for you)
