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====== Building a FreeNAS replication target on an Odroid HC2 ======

**THIS IS A VERY ROUGH WORK IN PROGRESS.  DON'T RELY ON THIS FOR ANYTHING OTHER THAN ENTERTAINMENT.  IT WILL EAT YOUR DATA, KICK YOUR DOG, AND POSSIBLY BURN YOUR HOUSE DOWN**

The [[https://www.hardkernel.com/main/products/prdt_info.php?g_code=G151505170472|Odroid HC2]] is a single-board computer that comes equipped with a SATA interface and a heatsink designed to mount a hard drive.  It's designed to serve as a simple home NAS, and a version of OpenMediaVault is available specifically for the HC2.  However, the board runs Linux, and there's also an OS image of Ubuntu 18.04 available.  Since Ubuntu supports ZFS pretty well, it should be trivial to set up one of these to serve as a replication target for a FreeNAS system.  Or so I thought.

Unfortunately, the Ubuntu 18.04 image uses a 32-bit kernel, and the available ZFS packages aren't compatible with a 32-bit kernel.  This means I'll need to compile the ZFS pieces myself, and they're not known to be stable with a 32-bit kernel in any event.  Updates to come.
===== Create a non-privileged user with sudo capability =====
<code>
adduser fred
usermod -aG sudo fred
</code>
===== Install the kernel headers =====
In order to build ZFS, you must have the headers for the running kernel installed on the system.
<code>
wget http://deb.odroid.in/5422-s/pool/main/l/linux-source-4.14.73-136/linux-headers-4.14.73-136_20181001_armhf.deb
sudo dpkg -i linux-headers-4.14.73-136_20181001_armhf.deb
</code>

===== Build ZFS on Linux =====
These instructions are taken from the [[https://github.com/zfsonlinux/zfs/wiki/Building-ZFS|ZFSonLinux Wiki]].  First, install the necessary dependencies:
<code>
sudo apt install git build-essential autoconf libtool gawk alien fakeroot zlib1g-dev uuid-dev libattr1-dev libblkid-dev libselinux-dev libudev-dev parted lsscsi ksh libssl-dev libelf-dev
</code>
Then download, build, and install the ZFS code:
<code>
git clone https://github.com/zfsonlinux/zfs
cd zfs
git checkout master
sh autogen.sh
./configure
make -s -j$(nproc)
sudo make install
</code>
Then load the ZFS modules:
<code>
sudo modprobe zfs
</code>

===== Create the pool =====
Create your pool.  Make sure to set ''ashift=12''.
<code>
zpool create -o ashift=12 dozer /dev/disk/by-id/ata-WDC_WD80EMAZ-00M9AA0_VAGA2PLD
</code>

===== Enable encryption, and create an encrypted dataset =====

The idea of this system is to be a standalone storage "brick", which could be left at a remote location where you might not fully trust the network operator.  ZFS on Linux supports dataset encryption for this purpose, and material for this section is drawn from this [[https://datacenteroverlords.com/2017/12/17/zfs-on-linux-with-encryption-part-2/|blog post]].  You'll first need to enable that feature on your pool:
<code>
zpool set feature@encryption=enabled dozer
</code>
Then, create the encrypted dataset:
<code>
zfs create -o encryption=on -o keylocation=prompt -o keyformat=passphrase dozer/encrypted
</code>
The system will prompt you for a passphrase, which you'll need whenever you mount that dataset.  Minimum length is eight characters.

===== Create a replication user =====
For the sake of security, it would be best if replication to this device ran as a user other than root.  First, create a user in the FreeNAS web GUI called ''zfsuser''.  Note the numeric userid for that user.

Then, on the Odroid, as root, run
<code>
adduser zfsuser -u userid -s /bin/false
</code>
where "userid" is the numeric user ID noted on the FreeNAS box.

Now allow that user to make changes on the encrypted dataset:
<code>
zfs allow -ldu zfsuser create,destroy,diff,mount,readonly,receive,release,send,userprop dozer/backup
</code>
===== Install Zerotier =====
[[https://zerotier.com/|Zerotier]] will create an encrypted virtual network connection between your Odroid and your FreeNAS box.  It's installed by default on FreeNAS, but you'll need to install it on the Odroid.  Run these commands:
<code>
sudo apt install curl
curl https://install.zerotier.com | sudo bash
</code>