#
# Boot Linux Live CD with ZFS support
# fearedbliss maintains a variant of System Rescue CD that is highly recommended:
# https://wiki.gentoo.org/wiki/User:Fearedbliss
# Instruction for a USB key version
# http://www.sysresccd.org/Sysresccd-manual-en_How_to_install_SystemRescueCd_on_an_USB-stick

# Create pool
zpool create -f -o ashift=12 -o cachefile=/tmp/zpool.cache -O normalization=formD -m none -R /mnt/gentoo -d -o feature@async_destroy=enabled -o feature@empty_bpobj=enabled -o feature@lz4_compress=enabled -o feature@spacemap_histogram=enabled -o feature@enabled_txg=enabled -o feature@extensible_dataset=enabled -o feature@bookmarks=enabled rpool /dev/sda

# Create rootfs
zfs create -o mountpoint=none rpool/ROOT
zfs create -o mountpoint=/ rpool/ROOT/gentoo

# Create home directories
zfs create -o mountpoint=/home rpool/HOME
zfs create -o mountpoint=/root rpool/HOME/root

# Create portage directories
zfs create -o mountpoint=none -o setuid=off rpool/GENTOO
zfs create -o mountpoint=/usr/portage -o atime=off rpool/GENTOO/portage
zfs create -o mountpoint=/usr/portage/distfiles rpool/GENTOO/distfiles

# Create portage build directory
zfs create -o mountpoint=/var/tmp/portage -o compression=lz4 -o sync=disabled rpool/GENTOO/build-dir

# Create optional packages directory
zfs create -o mountpoint=/usr/portage/packages rpool/GENTOO/packages

# Create optional ccache directory
zfs create -o mountpoint=/var/tmp/ccache -o compression=lz4 rpool/GENTOO/ccache

# Download stage3
wget 'ftp://gentoo.osuosl.org/pub/gentoo/releases/amd64/autobuilds/current-stage3-amd64/stage3-amd64-[0-9]*.tar.bz2'

# Extract stage3
tar -xvjpf stage3-amd64-*.tar.bz2 -C /mnt/gentoo

# Copy zpool.cache into chroot
mkdir -p /mnt/gentoo/etc/zfs
cp /tmp/zpool.cache /mnt/gentoo/etc/zfs/zpool.cache

# Copy resolv.conf into chroot
cp /etc/resolv.conf /mnt/gentoo/etc/resolv.conf

# Mount filesystems
mount -t proc none /mnt/gentoo/proc
mount --rbind /dev /mnt/gentoo/dev
mount --rbind /sys /mnt/gentoo/sys

# chroot
chroot /mnt/gentoo /bin/bash
env-update; source /etc/profile; export PS1="(chroot) $PS1"; cd

# Get portage snapshot (use OSUOSL mirror because it is usually fast)
env GENTOO_MIRRORS="http://gentoo.osuosl.org" emerge-webrsync

# Install genkernel
emerge sys-kernel/genkernel

# Install sources
emerge sys-kernel/gentoo-sources

# Build initial kernel (required for checks in sys-kernel/spl and sys-fs/zfs)
# FIXME: Make genkernel support modules_prepare
genkernel kernel --no-clean --no-mountboot

# Install ZFS
echo "sys-kernel/spl ~amd64" >> /etc/portage/package.accept_keywords
echo "sys-fs/zfs-kmod ~amd64" >> /etc/portage/package.accept_keywords
echo "sys-fs/zfs ~amd64" >> /etc/portage/package.accept_keywords
emerge sys-fs/zfs

# Add zfs to boot runlevel
rc-update add zfs-import boot
rc-update add zfs-mount boot
rc-update add zfs-share default
rc-update add zfs-zed default

# Install gptfdisk
emerge sys-apps/gptfdisk

# Make BIOS Boot Partition (make certain /dev/sda is your actual block device!)
sgdisk --new=2:48:2047 --typecode=2:EF02 --change-name=2:"BIOS boot partition" /dev/sda

# Flush the page cache to ensure GRUB2 sees the latest disk content
echo 1 > /proc/sys/vm/drop_caches

# Install GRUB2
mkdir -p /etc/portage/profile/package.use.mask
mkdir -p /etc/portage/package.use
echo "sys-boot/grub:2 -libzfs" >> /etc/portage/profile/package.use.mask/zfs
echo "sys-boot/grub:2 libzfs" >> /etc/portage/package.use/zfs
echo "sys-boot/grub:2 ~amd64" >> /etc/portage/package.accept_keywords
emerge sys-boot/grub:2
touch /etc/mtab

# Install GRUB2 to disk (make certain /dev/sda is your actual block device!)
grub-install /dev/sda

# We must create an empty configuration file so genkernel fines the right one.
touch /boot/grub/grub.cfg

# Build kernel and initramfs
genkernel all --no-clean --no-mountboot --zfs --bootloader=grub2 --callback="emerge @module-rebuild"

# Comment the BOOT, ROOT and SWAP lines in /etc/fstab
sed -i -e "s/\(.*\)\/\(BOOT\|ROOT\|SWAP\)\(.*\)/\#\1\/\2\3/g" /etc/fstab

#
# Follow chapters 8 through 12 of Gentoo Handboook: http://www.gentoo.org/doc/en/handbook/
#

# Make recovery snapshot after booting into new install
zfs snapshot rpool/ROOT/gentoo@install

# Additional tips

# ARC tuning - You can configure the RAM that ARC uses in bytes
echo options zfs zfs_arc_max=536870912 >> /etc/modprobe.d/zfs.conf

# Set portage niceness to minimize potential for updates to cause lag
echo PORTAGE_NICENESS=19 >> /etc/make.conf

# Set portage to compile in a CGROUP to minimize lag
cat << END > /usr/local/sbin/portage-cgroup
#!/bin/sh
# $1 must be the portage PID

cgroup=$(mktemp -d --tmpdir=/sys/fs/cgroup/cpu portage-XXXX) &&
echo $1 > "${cgroup}/tasks" &&
echo 1 > "${cgroup}/notify_on_release"
echo 256 > "${cgroup}/cpu.shares"
END
chmod u+x /usr/local/sbin/portage-cgroup
echo 'PORTAGE_IONICE_COMMAND="/usr/local/sbin/portage-cgroup \${PID}"' >> /etc/make.conf

# Swap support
zfs create -o sync=always -o primarycache=metadata -o secondarycache=none -b 4K -V 8G rpool/swap
mkswap -f /dev/zvol/rpool/swap
zfs snapshot rpool/swap@install
# Edit fstab to use swap here

#
# Note: Integrate `zfs create -o mountpoint=/home/user rpool/HOME/user` into procedure
#