[Dnsmasq-discuss] dhcp vendor-option and grub net_pxe_extensionspath

Simon Kelley simon at thekelleys.org.uk
Fri May 12 15:30:26 BST 2017


On 11/05/17 23:22, Carl Karsten wrote:
> I am pondering something I am not sure I even want: I guess we can call
> it a default option 209
> 
> Is this valid, reliable, predictable?
> 
> dhcp-option-force=209,"partman-auto/disk=/dev/sda"
> 
> dhcp-host=00:26:9e:03:9d:e5,set:negk,negk
> dhcp-option-force=tag:negk,209,"partman-auto/disk=/dev/sdb"
> 
> 
> The hope is ...sda except for the tag:negk case.

Yeah, that's how it's defined to work: and option which is conditional
on a tag gets used in preference to one which is not conditional, of the
tag is set.


Cheers,

Simon.

> 
> personally I only touch 20 machines a year, so setting up the extra 19
> lines
> is easy.  I like to understand my tools, and maybe someone with 100''s
> will be interested in my setup.  probaly not ;)
> 
> 
> 
> 
> On Sun, Apr 30, 2017 at 11:58 PM, Carl Karsten <carl at nextdayvideo.com
> <mailto:carl at nextdayvideo.com>> wrote:
> 
>     woked - yay.
> 
>     dhcp-host=00:26:9e:03:9d:e5,set:negk,negk
>     dhcp-option-force=tag:negk,209,"partman-auto/disk=/dev/sda"
> 
>     # grub/grub.cfg
>     net_get_dhcp_option appends ${net_default_interface} 209 string
> 
>     menuentry "Install Ubuntu preseed" {
>     set gfxpayload=keep
>     linux /ubuntu-installer/amd64/linux gfxpayload=800x600x16,800x600
>     --- auto=true url=dc10b DEBCONF_DEBUG=5 tasks="" hostname=
>     interface=${net_default_mac} ${appends}
>     initrd /ubuntu-installer/amd64/initrd.gz
>     }
> 
>     ~ # head /var/log/syslog
>     May  1 04:30:40 kernel: [    0.000000] Command line:
>     BOOT_IMAGE=/ubuntu-installer/amd64/linux
>     gfxpayload=800x600x16,800x600 --- auto=true url=dc10b
>     DEBCONF_DEBUG=5 tasks= hostname= interface=00:26:9e:03:9d:e5
>     partman-auto/disk=/dev/sda
> 
> 
> 
>     On Fri, Apr 28, 2017 at 5:53 PM, Simon Kelley
>     <simon at thekelleys.org.uk <mailto:simon at thekelleys.org.uk>> wrote:
> 
>         On 27/04/17 17:42, Carl Karsten wrote:
>         > I am looking for the syntax of dhcp vendor options, and then how to
>         > access them in grub-net.  I think.  maybe there is a better way.
>         >
>         > I pxe boot grub, which boots di (Debian Installer) and pass a preseed file.
>         >
>         > I am trying to work out a nice way to pass host specific info to di
>         > example, most use:
>         > partman-auto/disk="/dev/sda"
>         > but one machine has an onboard ssd nvme which needs /dev/nvme0n1
>         >
>         > di will read values appended to the kernel boot line, so I can hard code
>         > it like this:
>         >
>         > menuentry "Install Ubuntu preseed" {
>         > set gfxpayload=keep
>         > linux /ubuntu-installer/amd64/linux gfxpayload=800x600x16,800x600 ---
>         > auto=true url=dc10b hostname= partman-auto/disk="/dev/nvme0n1"
>         > interface=${net_default_mac}
>         > initrd /ubuntu-installer/amd64/initrd.gz
>         > }
>         >
>         > interface=${net_default_mac} - use the nic that pxe booted.
>         >
>         > Now I get lost in conf options and syntax.  forgive me for making stuff
>         > up here, if it worked I wouldn't be asking for help.
>         >
>         > I am hoping for something like
>         > partman-auto/disk=$(net_pxe_extensionspath/disk}
>         >
>         > in dnsmasq conf:
>         > dhcp-host=40:8d:5c:7f:bb:90,,gator
>         >
>         > dhcp-option-force=host:gator,209,"disk=/dev/nvme0n1"
>         >
> 
>         Look for "tags" in the man page, in this case, set a tag in the
>         dhcp-host line (it can be the same as the hostname)
> 
>         dhcp-host=40:8d:5c:7f:bb:90,set:gator,gator
> 
> 
>         and make the option conditional on that tag
> 
>         dhcp-option-force=tag:gator,209,"disk=/dev/nvme0n1"
> 
>         >
>         > So yeah, how do I send random strings based on mac/hostname
>         See above
> 
> 
>         > and how do I read what was sent in grub?
> 
>         Set the "log-dhcp" flag in the dnsmasq configuration to get lots of
>         useful information.
> 
>         Cheers,
> 
>         Simon.
> 
>         >
> 
> 
> 
>         > --
>         > Carl K
>         >
>         >
>         >
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