...
With both of these services in place any system which supports PXE/network-booting
should be able to gain an IP address, fetch a kernel, and boot without an installed operating system.
PXE uses three distinct network protocols that map to three server processes to perform the installation.
In our case, all three processes run on lcls-dev1 (LCLSDEV daemon)
(a) Dynamic Host Configuration Protocol (DHCP)
PXE uses DHCP to deliver initial network configuration options to client nodes.
The DHCP server supplies the PXE boot plug-in with
(i) IP address
(ii) TFTP server address
(iii) Stage 1 image boot-loader name from which to download and execute the image.
As the supplied PXE installation environments are non-interactive and will unconditionally reinstall a client machine,
we have the client associate its MAC address with a specific OS installation before starting the PXE boot.
The configuration information, in our case, in addition to IP/MAC address, includes a hostname and a pointer to the Master Starupt script in afs for our IOC.
It has an optional root-path variable pointing to the afs area which hosts the boot image that is served via TFTP.
This can be over-ridden as will be seen later.
When the Linux server is rebooted or power-cycled, PXE will attempt the network booting method first
and as a first step it will contact the DHCP server to retrieve the network configuration information.
Hence, every new linuxRT ioc (host) needs to be added to the DHCP server configuration file in afs.
This file is in /afs/slac/service/dhcp-pxe/dhcpd.conf
The IP/MAC address of the primary ethernet that will fetch the linuxRT boot image is defined here.
To add a new host to the DHCP configuration, contact Thuy.
Here's is an example - ioc-b34-bd32:
host ioc-b34-bd32 {
# SuperMicro (INTELx86)
#
hardware ethernet 00:25:90:D1:95:1E;
fixed-address 134.79.218.190;
option host-name "ioc-b34-bd32";
if ( substring( option vendor-class-identifier, 0, 5 ) = "udhcp" ) {
filename "/afs/slac/g/lcls/epics/iocCommon/ioc-b34-bd32/startup.cmd";
option root-path "afsnfs1:/afs/slac:/afs/slac";
}
}
(b) Trivial File Transfer Protocol (TFTP)
PXE uses TFTP that defines a simple UDP protocol for delivering files over a network.
PXE delivers kernels and initial bootstrap software to client nodes using TFTP.
In our case, we retrieve the linuxRT boot image from lcls-dev1 (LCLSDEV TFTP Server) from the following location:
/afs/slac/g/lcls/tftpboot/linuxRT/boot
In this location, there are several linuxRT-x86 bootimages.
These were custom-built by T.Straumann for the various Linux Servers/IPCs that we currently have setup to boot with linuxRT OS.
Of these images, '3.14.12-rt9' is the latest and it has in-built support for the
Broadcom networking ethernet chipset that are used in our dev Poweredge Dell Servers.
(c) Network File System (NFS)
The NFS service is used by the installation kernel to read all of the packages necessary to the installation process.
The NFS server therefore needs to provide access to the directory structure containing the PXE images.
This boot directory is available to all machines running NFS.
8. How do I start my IOC? Where is my ioc's statrup.cmd?
There are a few scripts that automate this process.
To begin with, there is the 'ipxe.ini' script in the tftp boot area /afs/slac/g/lcls/tftpboot/linuxRT/boot that PXE will run.
This is where the version of (linuxRT) kernel to run is specified as follows:
set vers 3.2.13-121108
This version number can be over-ridden by a chained, host-specific pxe init script to load an image different from the above:
chain ${hostname}.ipxe ||
For example, we have defined a script specifically for our ioc ioc-b34-bd32.ipxe which chooses to load the latest linuxRT image:
...
Example, from any lcls-dev host ssh to your ioc as 'laci':
ssh laci@ioc-b34-bd32
$ cd /afs/slac/g/lcls/epics/iocCommon/ioc-b34-bd32
Ensure that 'startupConsole-laci-rt.cmd' is in your current directory.
Start the virtual ioc as a foreground process:
./startupConsole-laci-rt.cmd
.
