ramroot pxe ram based rescue system ubuntu

gistfile1.txt

mkdir pxerescue
mkdir pxerescue/chroot
cd pxerescue
git clone https://github.com/medallia/ramroot
sudo debootstrap --arch=i386 xenial chroot http://apt/mirrors/ubuntu
sudo cp -r ramroot/initramfs-tools/* chroot/etc/initramfs-tools/
sudo chroot chroot
mount none -t proc /proc
mount none -t sysfs /sys
mount none -t devpts /dev/pts
export HOME=/root
export LC_ALL=C
apt install install initramfs-tools pixz
apt install linux-generic <--- can install linux-virtual for a smallrt kernel, but almost no modules included, usb keyboard won't work
apt autoremove --purge
apt clean
apt remove --purge resolvconf
rm /etc/resolv.conf
vi /etc/resolv.conf <-- add whatever you want
*FIX BUSYBOX* (see below)

passwd root (or enable autologin)
You can instead edit the file /lib/systemd/system/[email protected] and change the line
  ExecStart=-/sbin/agetty --noclear %I $TERM
to
  ExecStart=-/sbin/agetty --noclear -a root %I $TERM

change motd
- rm /etc/update-motd.d/*
- vi /etc/motd <--- whatever you want. You can also drop scripts in the above dir

** saving space / slimming down
echo -n '' > /var/cache/apt/pkgcache.bin
echo -n '' > srcpkgcache.bin
apt remove --purge <bunch of stuff linux-headers* and more, linux-firmware if you don't need it >
rm -rf /tmp/*

*** cleaning up and coming out of the image
umount -lf /proc
umount -lf /sys
umount -lf /dev/pts
exit the chroot

*** GET THE FILES YOU NEED TO BOOT
sudo cp chroot/{initrd,vmlinuz} .
sudo rm chroot/boot/{initrd,vmlinuz} <--- free up space, not needed in the image anyway, but need to install them for kernel modules and initrd generation
cd chroot
sudo tar Jcvf ../rootram.tar.xz .

==== Fix busybox ===
By default does not ship with wget and fails miserably
apt-get install -y gcc build-essential libncurses5-dev libpam0g-dev libsepol1-dev libselinux1-dev
wget busybox + extract
make defconfig
make clean && make LDFLAGS=-static
cp busybox chroot//usr/lib/initramfs-tools/bin/busybox

=== If you need a GUI ===
apt-get install xserver-xorg-core xorg fluxbox
can then startx

=== PXE setup ===
assumes you have pxe set up with lpxelinux + apache running
copy over vmlinuz initrd.img and ramtoot.tar.xz
menu stanza looks like this

LABEL 1
    MENU LABEL RamRoot
    KERNEL http://pxe/netinstall/ramroot/vmlinuz
    INITRD http://pxe/netinstall/ramroot/initrd.img
    APPEND boot=ramdisk ramroot=http://pxe/netinstall/ramroot/ramroot.tar.xz