Systemback-like simple script working for Ubuntu 18.10, etc

Below is a 'one step' bash script that creates an encrypted bootable livecd from an existing Ubuntu installation. (Tested/Working on Ubuntu 18.10)

Basically, the script copies the existing Ubuntu installation into a set of working directories at /tmp/livecd and:

- Uses chroot to add casper to the installation
- Modifies casper-helpers to add the encrypted squashfs booting functionality
- Creates the inital unencrypted squashfs housing the entire file system
- Uses a random string input to pre-encrypt a new encrypted squashfs file
- Uses an entered passphrase to then setup the encrypted squashfs file, create an ext4 file system, and then copy over the unencrypted squashfs file into it
- Finally, the entire encrypted bootable ISO (for squashfs files below 4GB) or IMG is created at /tmp/livecd/live-cd.iso or /tmp/livecd/live-cd.img

When the ISO/IMG is booted on the machine or in a VM, the encrypted squashfs is transfered completely into ram, the user is asked to enter the proper passphrase, and the squashfs is then unencrypted and used to boot the system.

The rsync command line string can be modified to add/remove items that are copied from the existing Ubuntu installation when the encrypted livecd is being created.

EDIT: *The script now handles images above the iso6990 4GB limit. If the created filesystem.squashfs file is above 4GB then a live-cd.img is created which is a bootable ext4 image housing the same files as the iso would have had. In addition, the script asks if you prefer to create and iso or an img when the filesystem.squahfs file is below the 4GB limit.*

livecd.sh:

#!/bin/bash

echo
echo Setting up /tmp/livecd
echo
sudo mkdir -p /tmp/livecd/cd/{casper,boot/grub} /tmp/livecd/chroot/rootfs /tmp/livecd/mnt

echo
echo Installing necessary packages
echo
sudo apt-get update
sudo apt-get install -y grub2 xorriso squashfs-tools cryptsetup

echo
echo Copying over existing system
echo
sudo rsync -av --one-file-system --exclude=/swapfile --exclude=/proc/* --exclude=/dev/* \
--exclude=/sys/* --exclude=/tmp/* --exclude=/lost+found \
--exclude=/var/tmp/* --exclude=/boot/grub/* --exclude=/root/* \
--exclude=/var/mail/* --exclude=/var/spool/* --exclude=/media/* \
--exclude=/etc/fstab --exclude=/etc/mtab --exclude=/etc/hosts \
--exclude=/etc/timezone \
--exclude=/etc/X11/xorg.conf* --exclude=/etc/gdm/custom.conf \
--exclude=/etc/lightdm/lightdm.conf --exclude=/tmp/livecd/chroot/rootfs / /tmp/livecd/chroot/rootfs

echo
echo Setting up links to chroot
echo
sudo mount --bind /dev/ /tmp/livecd/chroot/rootfs/dev
sudo mount -t proc proc /tmp/livecd/chroot/rootfs/proc
sudo mount -t sysfs sysfs /tmp/livecd/chroot/rootfs/sys
sudo mount -o bind /run /tmp/livecd/chroot/rootfs/run

echo
echo Processing chroot commands
echo
cat <<'ABC' | sudo chroot /tmp/livecd/chroot/rootfs /bin/bash
LANG=
apt-get update
apt-get install -y casper lupin-casper
cat >> /etc/cryptsetup-initramfs/conf-hook <<'DEF'
CRYPTSETUP=Y
DEF
patch -d /usr/share/initramfs-tools/scripts /usr/share/initramfs-tools/scripts/casper-helpers <<'GHI'
@@ -141,6 +141,13 @@
                 losetup -o "$offset" "$dev" "$fspath"
             else
                 losetup "$dev" "$fspath"
+ modprobe dm-crypt
+ mkdir /mnt
+ echo "Enter passphrase: " >&6
+ cryptsetup --type plain -c aes-xts-plain64 -h sha512 -s 512 open "$dev" squash >&6
+ mount -t ext4 /dev/mapper/squash /mnt
+ dev="$(losetup -f)"
+ losetup "$dev" /mnt/filesystem.squashfs
             fi
             echo "$dev"
             return 0
GHI
depmod -a $(uname -r)
update-initramfs -u -k $(uname -r)
apt autoremove
apt clean
find /var/log -regex '.*?[0-9].*?' -exec rm -v {} \;
find /var/log -type f | while read file
do
        cat /dev/null | tee $file
done
rm /etc/resolv.conf /etc/hostname
exit
ABC

echo
echo Copying chroot images to livecd
echo
export kversion=`cd /tmp/livecd/chroot/rootfs/boot && ls -1 vmlinuz-* | tail -1 | sed 's@vmlinuz-@@'`
sudo cp -vp /tmp/livecd/chroot/rootfs/boot/vmlinuz-${kversion} /tmp/livecd/cd/casper/vmlinuz
sudo cp -vp /tmp/livecd/chroot/rootfs/boot/initrd.img-${kversion} /tmp/livecd/cd/casper/initrd.img
sudo cp -vp /tmp/livecd/chroot/rootfs/boot/memtest86+.bin /tmp/livecd/cd/boot

echo
echo Removing chroot links
echo
sudo umount /tmp/livecd/chroot/rootfs/proc
sudo umount /tmp/livecd/chroot/rootfs/sys
sudo umount /tmp/livecd/chroot/rootfs/dev

echo
echo Creating the squashfs file
echo
sudo mksquashfs /tmp/livecd/chroot/rootfs /tmp/livecd/filesystem.squashfs -noappend

echo
echo Setting up encrypted squashfs file
echo
size=$(du --block-size=1 /tmp/livecd/filesystem.squashfs | awk '{print $1}')
((size=size+size/10))
((size=size/1024))
echo $size
sudo dd if=/dev/zero of=/tmp/livecd/cd/casper/filesystem.squashfs bs=1024 count=$size status=progress
dev="$(losetup -f)"
sudo losetup "$dev" /tmp/livecd/cd/casper/filesystem.squashfs

echo
echo Enter a large string of random text below to setup the pre-encryption.
echo
sudo cryptsetup --type plain -c aes-xts-plain64 -h sha512 -s 512 open "$dev" squash

echo
echo Pre-encrypting entire squshfs with random data
echo
sudo dd if=/dev/zero of=/dev/mapper/squash bs=1M status=progress
sync
sync
sync
sync
sudo cryptsetup close squash

echo
echo Enter the desired passphrase for the encrypted livecd below.
echo
sudo cryptsetup --type plain -c aes-xts-plain64 -h sha512 -s 512 open "$dev" squash

echo
echo Creating ext4 into encrypted container
echo
sudo mkfs.ext4 -m 0 /dev/mapper/squash
sudo mount -t ext4 /dev/mapper/squash /tmp/livecd/mnt

echo
echo Moving unencrypted squashfs file into encrypted sqaushfs container
echo
sudo mv /tmp/livecd/filesystem.squashfs /tmp/livecd/mnt
sync
sync
sync
sync
sudo umount /tmp/livecd/mnt
sudo cryptsetup close squash
sudo losetup -d "$dev"

echo
echo Creating size and md5sum cd files
echo
echo -n $(sudo du -s --block-size=1 /tmp/livecd/chroot/rootfs | tail -1 | awk '{print $1}') | sudo tee /tmp/livecd/cd/casper/filesystem.size
find /tmp/livecd/cd -type f -print0 | sudo xargs -0 md5sum | sed "s@/tmp/livecd/cd@.@" | grep -v md5sum.txt | sudo tee -a /tmp/livecd/cd/md5sum.txt

echo
echo Creating grub.cfg for the livecd
echo
sudo bash -c 'cat > /tmp/livecd/cd/boot/grub/grub.cfg <<EOF
set default="0"
set timeout=10

menuentry "Ubuntu GUI from RAM" {
linux /casper/vmlinuz boot=casper toram quiet
initrd /casper/initrd.img
}

EOF'

filesize=$(sudo du --block-size=1 -s /tmp/livecd/cd/casper/filesystem.squashfs | tail -1 | awk '{print $1}')

echo "filesystem.squashfs size: $filesize"

devflag=0

if [ $filesize -lt 4294967295 ]
then
 echo
 echo filesystem.squashfs is under the 4GB iso6990 limit
 echo
 echo "Create a bootable iso or bootable device img for (usb, hd)?"
 select yn in "iso" "dev"; do
     case $yn in
  iso ) echo;
   echo Creating bootable ISO at /tmp/livecd for the now encrypted livecd;
   echo;
   sudo grub-mkrescue -o /tmp/livecd/live-cd.iso /tmp/livecd/cd;
   echo
   echo COMPLETE!
   echo
   break;;
  dev ) devflag=1;
   break;;
     esac
 done
else
 devflag=1
fi

if [ $devflag -eq 1 ]
then
 echo
 echo Setting up /tmp/livecd/live-cd.img
 echo
 filesize=$(sudo du -s --block-size=1 /tmp/livecd/cd | tail -1 | awk '{print $1}')
 ((filesize=filesize+filesize/10))
 ((filesize=filesize/1024))
 sudo dd if=/dev/zero of=/tmp/livecd/live-cd.img bs=1024 count=$filesize status=progress
 dev="$(losetup -f)"
 sudo losetup $dev /tmp/livecd/live-cd.img
 echo
 echo Formating /tmp/livecd/live-cd.img to ext4
 echo
 sudo mkfs.ext4 -m 0 $dev
 echo
 echo Installing grub and copying live system files
 echo
 sudo mount -t ext4 $dev /tmp/livecd/mnt
 sudo grub-install --no-floppy --force --root-directory=/tmp/livecd/mnt $dev
 sudo rsync -av --one-file-system /tmp/livecd/cd/ /tmp/livecd/mnt
 sync
 sync
 sync
 sync
 sudo umount /tmp/livecd/mnt
 sudo losetup -d $dev
 echo
 echo COMPLETE!
 echo live-cd.img can now be written to a usb or hard drive using dd or similar
 echo
fi