Thanks to mika for the detailed response. Here is my detailed use case.
I plan to install linux to two partitions of each computer in a Univ. computer classroom
using only one usb flash drive containing a customized grml and a customized
linux mint 20 ulyana.
1. Boot one computer into ulyana, with a grml kvm running inside but bridged
to the host's network as the pxe server.
2. Start pxe service serving grml image, with the "netscript=http://..." option
pointing to a pdmenu script full of admin options (details below).
3. Boot all other computers using pxe into grml and into the pdmenu script.
4. For each computer, choose from pdmenu the option to prepare the partitions,
one EFI and the other LVM with all required volumes. Also install grml
using extlinux into the EFI partition, with an additional (not-yet usable) ulyana entry.
5. For each computer, choose from pdmenu the option to receive, in parallel,
the rather large ulyana image using udp-receiver.
6. From the pxe server use udp-sender to start broadcasting the ulyana image.
7. For each computer, choose from pdmenu the option to mount the ulyana image
and copy files inside into an LVM volume, completing the ulyana installation.
Some computers may go wrong after some use. A student should be able to
choose to boot the computer using pxe and repair/re-initialize his own computer
using options in the pdmenu (this time using wget instead of udp-receive).
This may happen without requiring the teacher to pay attention while he (me)
gives the lecture and while other students are using their ulyana in the classroom.
This computer classroom may boot into windows in other class hours.
There is already an existing DHCP service running all the time,
and It is best not to disrupt this service. So my pxe server should be a proxy server,
which only provides boot-related files but does not hand out IP's.
Actually I have created a customized version of grml with manually installed
pxelinux, dnsmasq, udpcast, pdmenu, gdisk, ntfs-3g, apache2, ...
and have tested individual steps separately. So my problem is kind of solved now.
Still it would be nice if grml comes with all of these pre-installed and even
with some sample pdmenu script so that computer lab admins (in Taiwan's
high schools and primary schools these are mainly busy computer teachers)
can see that GNU/Linux and in particular grml can save a lot of work for them.
Maybe even helping them distributing windows images (yuk).
I would also like to take this opportunity to thank you all contributors
for your great work on grml! It has saved me on several occasions
since I started using it around 2017. I have it in each and every one of
my bootable usb flash drive. I carry 3 of them with me all the time.
They give me great peace of mind :-)
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Greg Chao-Kuei Hung 洪朝貴
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