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Raspbian

Basic installation instructions for netbooting Raspberry Pi clients from a Raspbian chroot on an LTSP server.

Prerequisites

The LTSP server should already be configured by following the installation page. If booting x86 clients is also required, do that part first as it's easier.

Client configuration

This method has been tested with Raspbery Pi 2, 3B+ and 4.

  • To netboot Pi 2, format an SD card with the fat file system and put only bootcode.bin in it. This file can be found in /boot/bootcode.bin inside your Raspbian image.
  • Pi 3B+ supports netbooting out of the box.
  • Pi 4 shipped without netbooting code, so it currently needs an eeprom update. I used /lib/firmware/raspberrypi/bootloader/beta/pieeprom-2020-01-09.bin and I followed the instructions from /lib/firmware/raspberrypi/bootloader/raspberry_pi4_network_boot_beta.md.

Chroot preparation

Raspbian is very optimized for Raspberries, so it's currently a better option than e.g. Ubuntu MATE or other distributions. The easiest way to generate a Raspbian chroot isn't with the debootstrap command, but by downloading Raspbian. You may also follow the Raspbian installation guide or you may use dd to read the SD card from an existing Raspbian; to keep the instructions shorter, we assume that in the end you have an uncompressed raspbian.img on the LTSP server.

losetup -rP /dev/loop8 2019-09-26-raspbian-buster.img
mount -o ro /dev/loop8p2 /mnt
time cp -a /mnt/. /srv/ltsp/raspbian
umount /mnt
mount -o ro /dev/loop8p1 /mnt
cp -a /mnt/. /srv/ltsp/raspbian/boot/
umount /mnt
losetup -d /dev/loop8

At this point, Raspbian should be in /srv/ltsp/raspbian. This chroot isn't ready for netbooting yet, the following commands are needed:

# Go to the chroot in order to use relative directories
cd /srv/ltsp/raspbian
# Mask services that we don't want in netbooting
systemctl mask --root=. dhcpcd dphys-swapfile raspi-config resize2fs_once
# Remove SD card entries from fstab
echo 'proc            /proc           proc    defaults          0       0' >./etc/fstab
# Use an appropriate cmdline for NFS_RW netbooting
echo 'ip=dhcp root=/dev/nfs rw nfsroot=192.168.67.1:/srv/ltsp/raspbian,vers=3,tcp,nolock console=serial0,115200 console=tty1 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles modprobe.blacklist=bcm2835_v4l2' >./boot/cmdline.txt

Server preparation

In ltsp.conf, set RPI_IMAGE to the chroot name. This will be used by ltsp kernel to generate the appropriate symlinks from /srv/tftp/* to /srv/ltsp/raspbian/boot/*.

[server]
RPI_IMAGE="raspbian"

Then, run:

ltsp kernel raspbian
ltsp initrd
ltsp nfs

NFS_RW netbooting

At this point we're ready to netboot a single client in NFS_RW mode. This means that whatever changes we do on that client, like installing new programs, are directly saved in /srv/ltsp/raspbian.

First, export the chroot in NFS read-write mode:

echo '/srv/ltsp/raspbian  *(rw,async,crossmnt,no_subtree_check,no_root_squash,insecure)' >/etc/exports.d/ltsp-raspbian.exports
exportfs -ra

You may replace * with an IP to only allow access to a single client, or you may delete the /etc/exports.d/ltsp-raspbian.exports file when you're done, so that there are no security issues.

Now boot a single client, add the LTSP PPA to your sources, and install the client-side packages:

apt install --install-recommends ltsp epoptes-client

LTSP mode netbooting

At this point our chroot contains the LTSP code and is ready to be netbooted. But it needs a different kernel cmdline than the NFS_RW mode, so run the following commands:

echo 'ip=dhcp root=/dev/nfs nfsroot=192.168.67.1:/srv/ltsp/raspbian,vers=3,tcp,nolock init=/usr/share/ltsp/client/init/init ltsp.image=images/raspbian.img console=serial0,115200 console=tty1 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles modprobe.blacklist=bcm2835_v4l2' >/srv/ltsp/raspbian/boot/cmdline.txt

# Finally, create the squashfs image
ltsp image raspbian --mksquashfs-params='-comp lzo'

That's it, now you should be able to netboot all your Raspberry Pi clients.

At your convenience, also check out some common Raspbian issues.