In my last installment, I discussed the hardware I was planning to buy for the build of my new home NAS server. Well, I got all the parts within a matter of days and threw the thing together, then spent my spare time over a couple of weekends setting the thing up. In this post, I’ll discuss the basic setup of the OS (Ubuntu server).
Installing Ubuntu Server 12.10
There are a lot of competent Linux distributions out there. I first got into Linux with Redhat in the late nineties, went through a Slackware phase, and finally found something I liked in Debian around 2001. Debian had an excellent package management system (apt), which made keeping all the software on your computer up-to-date. Fast forward a decade, and I’m still there, although with the Debian derivative Ubuntu. Ubuntu has the widest and deepest selection of pre-built software that I know of, and it is still a joy to work with.
Creating a bootable USB install disk
You may have noticed that my new server has no optical drive. So, I had to create a bootable USB stick with the Ubuntu installer. I did this by sticking a cheap 2GB flash drive I had lying around into my OS X 10.8 Mac Mini and then firing up Disk Utility. I formatted the disk FAT with an MBR boot record (GUID won’t allow boot), then added following incantation from the terminal:
# sudo fdisk -e /dev/disk2 f 1 write exit
Which (I think) activates the first partition for boot.
Then, I used unetbootin to download and image the installer (ubuntu-12.10-server-amd64.iso) onto the disk. I popped it in the NAS and it booted right up!
I won’t hold your hand through the entire installation process. I did a no-frills install:
- selected a hostname (“nasty,” heh),
- whole-disk LVM on the SSD,
- only installed OpenSSH server
- installed grup on the root of the SSD
That's it! Ubuntu installed.
Setting up the RAID volume
There are a lot more options out there for Linux RAID and filesystems than there were a few years ago. The last time I set up a NAS, I tried out ZFS with its whizzy volume management and snapshotting and whatnot, but discovered it was slow, unstable, and RAM-hungry. Before that I’d tried JFS, Reiser, and others. I was always bitten by their immaturity, and a lack of disaster recovery tools. Meanwhile, good old ext has always been reliable if not the most feature-rich. And, perhaps most importantly, ext is always supported by every recovery tool. So I decided to stay simple and just use Linux’s built-in software raid with an ext4 filesystem for my big media volume.
Before setting up a Linux software RAID volume, you should probably do some reading. It’s actually very simple once you figure out what you want, but figuring that out can be a lengthy process. I’ll direct you to the canonical guide that I’ve used several times in the past. For me, it boiled down to a 4-disk RAID5 array (one disk worth of parity) with a 256KB chunk size (since I mostly have large media files):
mdadm --create --verbose /dev/md0 --level=5 --chunk=256 --raid-devices=4 /dev/sda /dev/sdb /dev/sdc /dev/sdd
And that’s it! Once the creation is started, you can start sticking stuff on the volume right away, so I went ahead and created a filesystem:
mkfs.ext4 -v -m .1 -b 4096 -E stride=64,stripe-width=192 /dev/md0
Here, the ‘-m .1′ reserves just 0.1% of the volume’s space for the root user (down from the default of 5%), and the block and stride arguments are tuned for the raid block size. See this section of the guide for info on how to compute them.