Mosh is something i’ve been meaning to give a go for a while now… but have never had the chance. Recently however, on a train from Rome to Florence, I got a little tired of reconnecting SSH sessions and re-attaching screen’s / tmux’s. Then I remembered… Mosh!

Some examples of why / when to use Mosh

Dubbed “the mobile shell” mosh is simple, it requires you have the mosh binaries installed on both client, and server, and that you have permission to SSH to said server (you don’t need a root account). Then mosh will create an initial SSH session, which it in-turn uses to create a UDP connectionless “session” between mosh running on the server and mosh running on the client.

Why?

Well… I can type mosh username@server.tld start a nice terminal session, close my laptop / phone, come back 4 hours later, open my laptop… and carry on. It’s also very useful for environments where your connectivity is poor or you have a dodgy ISP supplied Router that can’t sustain SSH connections very well.

$ mosh username@hostname.tld

Directly, stolen inspired from the original website. Mosh will log the user in via SSH, then start a connection on a UDP port between 60000 and 61000.

Beyond just having a really stable “connection” to a remote Terminal session. Mosh also has some quite cool features, that users of other modern shells will appreciate, such as auto complete of common commands and also a nifty indicator bar to tell you if something is up with the connection.

All in all, give mosh a go, it took me less than 120 seconds to get up and running. If you hate dead ssh sessions and can’t wait for timeouts, then what are you waiting for . As usual, hit me up at @italoarmstrong on twitter if you want banter.

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I recently changed from having Dedicated Servers to renting co-location rackspace directly in a datacenter. What this meant was that the “density” of CPU:Power ratio was important. Say for example you rent 1U of rackspace, that will come with some amount of power, measured in FLOOR(0.9*(AMPS=(WATTS / VOLTS)) during “peak” or “boot” power usage… with a total allocation of say 0.4 amps, along with bandwidth etc.

So why a Mac Mini for this purpose? Take for example a Dell Poweredge 1U Server… fits perfectly in the 1U of space provided and can consume a lot of power, 0.5+ so really, you can only squeeze 1 of these in without paying over-ages… at a push. What it does give you over a Mac Mini though, is the possibility to have 128GB RAM and 4 HDD bays in a single chassis, but at a much higher power cost. Lets take for example the Mac Mini… I’m colocating 4 Late 2012, Core i7 Mac Mini’s with 16GB RAM and 2TB hard drive space in EACH. Due to the way in which the Mac Mini was engineered, these consume around 0.19 AMPS each. Making the “density” increase, so in my 0.4 allocation, I can place 2 Mac Mini’s without incurring additional charges… thats 8 Physical Core i7 Cores… 32GB RAM and 4TB Hard drive space… in a piece of metal that is easily and readily available/replaceable and modular…

Those datacenter savvy people amoung you will now be thinking… ah, what about cooling, what about remote reboots etc… well there are solutions to all of that also, see my guide on Ubuntu 12.04 and 12.10 on a Late 2012 Mac Mini for a detailed howto.

The end result, you’re reading this blog post on a Centos VM hosted on a Debian KVM Based Hypervisor running on a Late 2012 Mac Mini! all setup and configured to be at a lower cost than any competitor and offering a really high density in a datacenter environment.

Wanna discuss, tweet me @italoarmstrong

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