Using custom variable to assign value to bootfile-name

karteek.challa at karteek.challa at
Tue Nov 17 18:20:16 UTC 2015

Hi Niall and Simon,

Thanks a ton for your inputs.
I have created the config files with only entry with the software version for each target and included them in the actual dhcp file. And gave full permission to these config files and only r&x permission to actual dhcp file.

I have one more query!
How can I calculate the string length in the dhcp file.
For example:
Option software-version "soft_v1_g2333.tar"
I want to know the length of "soft_v1_g2333.tar" in the dhcp conf file.
Is it possible? Is there any function similar to substring()?


-----Original Message-----
From: dhcp-users-bounces at [mailto:dhcp-users-bounces at] On Behalf Of Simon Hobson
Sent: den 11 november 2015 23:43
To: Users of ISC DHCP
Subject: Re: Using custom variable to assign value to bootfile-name

Niall O'Reilly <niall.oreilly at> wrote:

>  Variables don't do what you need.
>  I'ld suggest something like this, repeated for the other groups:
> group target_1 {
>  option boot-filename = "soft_1.tar";
> }

I think the problem he has is that if he allows the devs to edit that themselves, they screw up the rest of the config. I'm wondering if some include files (and perhaps some scripts) might work.

group target_1 {
 $INCLUDE soft1.cfg

Then generate a number of config files that you can use with the include statements. Either let the devs edit them directly, or let them work through a script that does some sanity checking.

Or put placeholders in the config, and have a script that replaces them with the desired values to generate a config file for the server to use.

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