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Frequently asked questions on NexentaCore

Frequently asked questions about NexentaCore - a distribution that combines the OpenSolaris kernel, ZFS and Ubuntu.

What is Nexenta?
Nexenta is a distribution based on the OpenSolaris kernel, the GNU C library and userland and the packages from Ubuntu Linux. Unlike OpenSolaris, Nexenta is able to use Debian's APT repositories, and there are thousands of packages available - 13,000 in the latest stable version.

Why would I want to use it over Ubuntu?
Well, the draw for most people is going to be ZFS - the Zetabyte File System - which is the most famous feature of Solaris and OpenSolaris. This is not available in Ubuntu as it has not yet been ported to the Linux kernel and there are some licensing issues. You can run it via Fuse, but this is not without its issues.

Sun has also just added support for ZFS deduplication, which means you can store more on your disks if files are repeated multiple times, as they are on most systems.

How can Nexenta provide ZFS with GNU packages?
In terms of the licensing, Linux is based on the GPL, while Solaris and ZFS uses Sun's CDDL. It's historically been said that ZFS can't be incorporated into Linux due to incompatibilites between the two licences. However, Nexenta reckons they are on "stable legal grounds", something it said became "extremely clear during recent GPL3 discussions.

Does it have a GUI?
When first installed you get a command line interface (CLI) only. You have to install the GUI. To install this type:

su -

apt-get update

apt-get install xorg gnome-core gdm

Xorg -configure

startx

Is Nexenta going to support ZFS deduplication?
Yes, apparently so. ZFS depulication has been hotly awaited and is seen as a killer feature, particularly for those in the storage world, and it's coming soon to Nexenta.

Basically, ZFS deduplication de-dupes data stored on your drive, so only a single copy of the file is kept. You set up your drive to use ZFS Dedup using a command that's as simple as "zfs set dedup=on poolname", and you can then store more data on the drive that it's true capacity!

For example, most people have various copies of the same files scattered all over their disks. So if you copied them to various places you'd use up all of your space. However, with dedup running, you can store much more on your disks because only a single copy exists. It's most amazing!

Why not just use OpenSolaris?
OpenSolaris is not quite as rich in packages as Ubuntu, nor is the community as active, so there are benefits over using Nexenta compared to OpenSolaris.

The latest stable release, NexentaCore Platform v2.0, is based on Ubuntu 8.04 LTS (long-term support), which is better known as Hardy Heron. It uses the 104+ build of OpenSolaris with critical patches and includes a load of popular packages, including dpkg, apt, gcc, binutils, Perl, Python, GTK, QT, Apache, MySQL and Exim4.

How do I install packages on a Nexenta system?
Nexenta uses APT, just as Debian and Ubuntu do. However, it also has a new tool called apt-clone, which uses ZFS's snapshotting features. To install a package using apt-clone, firstly you'd update the APT cache by running "apt-get update", just as you would from Debian.

This will fetch the latest package lists from the Nexenta APT repositories (it does not use the Debian or Ubuntu repositories) and cache them on your machine. When you've done that you'd enter "apt-clone -l" to list the available "boot environments. If you've never used apt-clone before, you should have just the one.

Now, suppose you wanted to run a "dist-upgrade" to update all of the packages on your machine, but you wanted to create a snapshot of the current state to allow you to roll the system back in case something failed. You can do this by entering the command "apt-clone dist-upgrade".

Nexenta will now grab all of the latest packages and install them, while creating an additional boot environment for you to rollback to if you need to.

Once you've done this press 'n' otherwise your system will reboot. Type "apt-clone -l" again and you should see another entry in the list of boot environments. If you reboot your system now you'll have an additional entry in your Grub boot loader, marked with the current date, allowing you to test the system or use the other boot environment if it's not working properly.

Can I create a ZFS root pool easily?
Yes, this is much easier to do than in Solaris or OpenSolaris. There's a specific option in the installer, which says "For mirrored ZFS-boot configuration please two or more equal-size disks."

Simply check the boxes next to the drives you want to use in your ZFS-boot mirror pool and Nexenta will set it up for you automatically.

Are there any derivative distributions?
Yes, if you prefer Xfce to Gnome, there's StormOS which is based off NexentaCore.

Is there a more modern version than NexentaCore 2.0?
Yes, this is the stable one, which is based off the ultra stable Ubuntu 8.04 LTS release. If you want the cutting edge stuff, either use the Alpha3 of NexentaCore 3.0 (NCP3 Alpha3) or wait a while until it goes stable. Obviously, it goes without saying that as it's an alpha release it isn't stable, so don't bother with this one on a production machine. It's based off the OpenSolaris b131 release and includes ZFS deduplication.