[SATLUG] diskless ramdisk booting

R P Herrold herrold at owlriver.com
Thu Jul 21 11:56:27 CDT 2016


> > Borries Demeler wrote:
> > > I am hoping someone on this list can explain how diskless booting works.
> > > 
> > > I have a bunch of high school kids in my lab this summer and we are
> > > trying to build a diskless linux cluster as a summer project. I have a
> > > bunch of generic boxes with quad-core processors, on board video and 8
> > > GB RAM each. We configured one of the boxes with CentOS 6.8 as a head
> > > node. It has dhcpd, tftpd, nfs working fine now.  We can successfully
> > > pxe boot various iso images served through the tftp server, the nodes
> > > get private IP addresses, tftp boot the kernels and ramdisks on the iso
> > > images, and the nodes can mount nfs shared volumes from the head node.
> > > All of this works fine.
> > > 
> > > We now wanted to build our own custom image and wanted to compile a
> > > minimal kernel and build a minimal ramdisk on which we could nfs mount
> > > various shares that hold the software and home directories we want to have
> > > accessible on the slave nodes.

it may well make sense here to use an older (known working) 
PXE, and TFTP client [see LTSP and an older K12 below], to 
confirm you have functionality ... iptables restrictions, and 
NFS as root (ot access a network swap and /home/) in NFSv4 are 
possible points of breakage that would probably not be 
accessible as security models ahve evolved

> > > But we so far have been unable to build a proper kernel or ramdisk that
> > > gets past the mounting point where the root ramdisk file system gets
> > > mounted and cannot figure out where we are going wrong. Any help would
> > > be appreciated. We tried to follow this guide to the T:
> > > 
> > > http://eduardo-lago.blogspot.com/2012/06/ram-only-pxe-boot-smallest-diskless.html 

It has been years since I set one of these installs up (I 
built a 200 seat diskless installation for a customer).  The 
LTSP, and Jim McQuillan's work are probably a trailhead to use
	http://www.ltsp.org/

As you can PXE boot, you are almost there.  I set one up on 
CentOS 6, but have not tried on C7 with the change to systemd 
in the boot time scripts

Fedora seems to have taken the torch for the k12 Linux variant
	https://fedorahosted.org/k12linux/

for a while, but the last time it seems to have been worked on 
there [ltsp-5.1.95-6.fc19.src.rpm] is at F20 (so perhaps three 
years ago)

good luck,

-- Russ herrold


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