nfs root path variable (pxe/nfs boot)

freeindy · 03-06-2008, 04:48 AM

Hi,

How can I pass, either by dhcpd.conf or by kernel boot parameter, a variable that is exported in host bash.

I have a target that boots from the host but I want the root path to be 'read' by host variable. For example,

in bash:
export TARGET="/my/root/path"

Passing by kernel boot parameter
nfsroot:xx.xx.xx.xx:$TARGET
THIS DOESN'T WORK. It passed :: mount $TARGET and got kernel panic.

In dhcpd.conf the variable is set as:
option Root-Path "/my/root/path"
and I don't know how to change it here.

Or is it possible by any other means?

Thanks
Ïndy

Wells · 03-07-2008, 02:08 PM

In your dhcpd.conf file, is that option passed as a global option or as one for a specific host? If it is as a global option, you should be able to override it for an individual host in that hosts' configuration section of the dhcpd.conf file.

beadyallen · 03-07-2008, 02:29 PM

I don't think it's possible to do what you want via an environment variable in the dhcpd.conf file. It's not interpreted as a shell script, so it won't work directly. I suppose you could have a sed script to make the changes, the restart dhcpd, but it'd be an ugly hack to say the least.

I do something similar to what you want but with symlinks for the root directory. In the config file, I've got a permanent nfs root entry as /mnt/nfsroots/currentroot. currentroot is actually a symlink to the directory I really want to export. I've got a shellscript that swaps the symlink between directories whenever I want to change filesystems. Actually, my kernel sent by tftp is a symlink too. Dead easy to test new images on my dreambox.

Why are you wanting to do this anyway?

freeindy · 03-11-2008, 09:19 AM

beadyallen,

I have targets that needs to run exactly the same distro but a few directories like /var /root /home needs to be different. So what I originally did was I had the distro at:

Code:

/tftpboot/images/distro

then i soft linked the whole distro to it:

Code:

/target1/distro/boot -> /tftpboot/images/boot
/target1/distro/etc -> /tftpboot/images/etc
/root

etc.

Now I know it doesn't work... mounted by nfs doesn't allow to have symlinks on top level. But what I'm doing now that works is:

in my /tftpboot/images/distro i have copies of root like:

Code:

/root_target1
/root_target2
...

/root -> root_target1

The thing is that the complete distro is 1.7G and I don't want to copy it for each target.

Then when it is tested on one distro, I need to do try another distro for exact same procedure. Instead of me re-writing the dhcpd.conf or kernel parameters all the time when I'm jumping between distros, I was hoping I could do this by simple environment variable or something

Indy