TweetFollow Us on Twitter

Mac in the Shell: Mass Remote Management with dshell

Volume Number: 24 (2008)
Issue Number: 01
Column Tag: Mac in the Shell

Mac in the Shell: Mass Remote Management with dshell

Or, mass remote management without ARD

by Edward Marczak

Introduction

A feature article this month covers methods to manage an army of Macs post-deployment. In other words, after they've been imaged and rolled out to the masses. The products and methods listed there are certainly applicable and appropriate for many situations. I'm going to describe yet another method that comes in handy in other situations. dsh, the distributed shell, can run a command over groups of machines that you specify. It performs this magic over ssh, so, you can affect machines over LAN or WAN links, near or far. Since OS X and other machines have ssh in their base distribution, you can command across platforms. This article explains how you, too, can send out commands to all or a group of your Macs - simultaneously - with a single press of the return key.

Getting the Goods

While there are many nice apps in the base distribution of OS X, dsh is not one of them. dsh is an agentless controlling app, so fortunately, you only need to retrieve, compile and install on one host, or any admin station that you need. You'll need a compiler on some station to compile the program - typically meaning having Apple's developer tools installed.

Two downloads are needed to get us going. Visit this page:

http://www.netfort.gr.jp/~dancer/software/downloads/list.cgi

and retrieve the latest versions of dsh and libdshconfig. As of this writing, they are:

http://www.netfort.gr.jp/~dancer/software/downloads/dsh-0.25.9.tar.gz

http://www.netfort.gr.jp/~dancer/software/downloads/libdshconfig-0.20.9.tar.gz

It's easy to take care of everything while in terminal: just use curl to download the files needed (use "curl -O http://.."), tar to unpack (tar xzvf filename) and then it's simple to compile. Both pieces of code compile cleanly in OS X 10.4 and 10.5, and install in /usr/local by default. Enter the libdshconfig directory that you just unpacked, and simply enter the following commands (your entries in bold):

$ ./configure
checking for a BSD-compatible install... /usr/bin/install -c
[output snipped]
config.status: creating Makefile
config.status: creating config.h
config.status: executing depfiles commands
$ make
make  all-am
[output snipped]
creating libdshconfig.la
(cd .libs && rm -f libdshconfig.la && ln -s ../libdshconfig.la libdshconfig.la)
$ sudo make install
Password:
/bin/sh ./mkinstalldirs /usr/local/lib
[output snipped]
 /usr/bin/install -c -m 644 libdshconfig.h /usr/local/include/libdshconfig.h

Next, we need to do the same for dsh itself. Change into the dsh directory you unpacked, and repeat the same process that you just went through for libdshconfig (configure, make, sudo make install). The entire process should take you less than 5 minutes. Literally.

While you can alter the install directory, I recommend that you leave the default values, and have the binaries and config files installed under /usr/local. I'll be referencing that as the install location throughout this article.

You can verify installation by typing "/usr/local/bin/dsh". You should be told, "dsh: no machine specified", and dsh would be right.

The configuration

Now that we have dsh installed on our administrative machine, how do we use it? Fortunately, under Leopard, /usr/local is a 'blessed' location, and is already in our $MANPATH. If you're using 10.4, you'll need to add "/usr/local/share/man" to $MANPATH and export it, or re-source your init file. dsh comes with some short-but-useful man pages. First, we'll need to update the configuration file.

If you left each application take the default values during their configure stage, and I recommend that you do, you'll find the main config file at /usr/local/etc/dsh.conf. We need to make one change to this file. So, whip out your favorite text editor, and change the line that reads:

remoteshell =rsh

to read:

remoteshell =ssh

(If you're daring, this can be achieved in one line with sed: sudo sed -i .back s/rsh/ssh/ dsh.conf). You may also want to change the "waitshell" value from "1" to "0". With a setting of 1, dsh will block execution until the previous machine has returned. As I said, you may want to change this. It's really applicable for very large rollouts. There's a man page available for the configuration file accessible with "man dsh.conf".

Determining the Target Machines

Before we continue, we need to take a step back and plan things out a bit. We need to determine which machines we're going to be targeting. Since we've chosen ssh as the remote mechanism, each machine that we're going to want to control needs ssh enabled. Now a days, this is the default for most platforms and distributions. That said, unless we want to enter our password each time we make a dsh run, we're going to want to create a public key and install it on any machine that we want to administer. Also, we also need a list of computers for dsh. This list basically tells dsh, "hey - run this command on all of these machines."

ssh was covered extensively in this column in the October 2007 issue, but, as a quick refresher, here's the sequence of creating a public key for ssh's use:

$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/admin/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /Users/admin/.ssh/id_rsa.
Your public key has been saved in /Users/admin/.ssh/id_rsa.pub.
The key fingerprint is:
6e:4b:ca:45:2d:c7:3d:14:d2:34:1e:ad:45:a5:fc:8e admin@machine-name.local

In this sequence, you simply press enter when asked for the passphrase and to verify. Notice that the output tells you that "your public key has been saved in...". Change directory to ~/.ssh. We need to copy the contents of the newly generated id_rsa.pub file to each machine that we're going to manage. Fortunately, this is a one-time step.

Easiest instructions to write: ssh to the machine you're going to target, using the admin-level account that you'll be running remote commands with:

ssh admin@remote.example.com

Once in, run this command:

ssh user@my.machine.com "cat ~/.ssh/id_rsa.pub" >> ~/.ssh/authorized_keys

where 'user' is the user account that you just had generate the key for, and "my.machine.com" is the machine where that user id resides - likely the machine you're on right now. Once done, type exit, and then try to ssh again. This time, you should not be asked for a password, but rather, simply receive a remote shell.

In the event that you cannot ssh back to your machine, you can always manually copy your key to the remote machine and add its contents to the ~/.ssh/authorized_keys file on the target account. For more about ssh, creating ssh keys and troubleshooting, see my ssh article in the October 200 issue of MacTech Magazine.

While you are accessing each remote machine, you need to keep a list of the account that you're accessing it with, and its fully qualified domain name (FQDN) or IP address. Once complete, take this list and enter it into /usr/local/etc/machines.list in this format:

/usr/local/etc/machines.list
nyadmin@ny.radiotope.com
caadmin@ca.radiotope.com
fladmin@fl.radiotope.com
azadmin@az.radiotope.com

Now comes the fun part!

Spreading the Joy

Let's start with a easy one: viewing the uptime statistics on all of the machines we've identified. This is as easy as:

$ dsh -a uptime 16:38 up 14 days, 9:27, 2 users, load averages: 0.19 0.13 0.16 16:38 up 59 days, 7:09, 1 user, load averages: 0.02 0.02 0.00 13:42 up 93 days, 3:25, 2 users, load averages: 0.02 0.02 0.00 1:39PM up 213 days, 4:01, 0 users, load averages: 0.12, 0.08, 0.04

It's a complete coincidence that those are in order of uptime! However, that raises the question: what order are they in? The "-M" switch will prepend the machine name before its output. Let's see that in action:

$ dsh -M -a uptime
nyadmin@ny.radiotope.com: 16:41  up 14 days,  9:30, 2 users, load averages: 0.47 0.27 0.21
fladmin@fl.radiotope.com: 16:41  up 59 days,  7:12, 1 user, load averages: 0.00 0.00 0.00
azadmin@az.radiotope.com: 13:45  up 93 days,  3:28, 2 users, load averages: 0.01 0.02 0.00
caadmin@ca.radiotope.com:  1:42PM  up 213 days,  4:04, 0 users, load averages: 0.04, 0.07, 0.04

There, that's a little better. The "-a" switch tells dsh to run the command against all machines that we've defined.

If you opted to not use a waitshell - your config file still has the line "waitshell =1" - you can override this at runtime using the "-c" switch. Also, if there's a machine that you have not added to your machines.list file, but want to use it ad-hoc, use the "-m" switch. Combining all of these options would look like this:

$ dsh -M -c -m txadmin@tx.radiotope.com -a 'last | head -1'
fladmin@fl.radiotope.com: fladmin  ttyp0    192.168.70.108   Thu Nov 29 15:22 - 15:22  (00:00)
caadmin@caadmin.radiotope.com: caadmin  ttyp1    192.168.70.108   Thu Nov 29 15:09 - 15:09  (00:00)
nyadmin@ny.radiotope.com: nyadmin  ttyp2    192.168.70.108   Thu Nov 29 12:29 - 12:29  (00:00)
Password:
txadmin@tx.radiotope.com: root      ttys000  w1.z2.nyc-ny.example.net Thu Nov 29 09:29 - 09:35  (00:05)
fladmin@fl.radiotope.com: fladmin          ttyp0    10.0.2.3       Thu Nov 29 13:37 - 13:37  (00:00)

In one fell swoop, this runs the command "last | head -1" on all machine defined in our machines.list file and additionally on "tx.radiotope.com". You'll see the "Password:" prompt in the output above as tx.radiotope.com wasn't preconfigured and is using password authentication. Once the (correct) password is entered, it happily gives us the output we're looking for, just like the other machines.

Final Tips

dsh is useful enough already, but how can we make our lives even easier? First, you may not always want to run all commands on all machines. There are two ways around this. One way is to use a group file. Simply create a file using the same format as machines.list and store it in /usr/local/etc/group/groupname. So, let's say we wanted to target all of our West Coast servers. We could create /usr/local/etc/group/west_coast and add to it:

/usr/local/etc/group/west_coast
waadmin@wa.radiotope.com
caadmin@ca.radiotope.com
oradmin@or.radiotope.com

Now, we can run commands against just this group:

$ dsh -M -g west_coast w

This will give us "who" (w) information from each server in the "west_coast" group.

Also, you can specify full server lists in an ad-hoc fashion. Create a file using the machines.list format, and specify it with the "-f" switch.

Nicely, if a machine definition ends up in multiple files, specifying it multiple times will be reduced to a single invocation.

The real magic here is that all input to dsh are simple text files. Decisions can be made, results grabbed from a database, files created on the fly and commands send to appropriate groups of machines. Think about how you could group machines: by location, by service (web, directory services), by class (PPC, dual-proc), by use (administrative, development), etc.

In Conclusion...

Despite the subhead, I don't believe dsh is meant to replace ARD. However, for server management, it may fit into your workflow better and can reach out to machines that ARD can't touch (think Linux or BSD servers...even Windows, with the right software and mindset). This can give you some incredible control over armies of machines. You have all the power of a shell on the remote machine. You can be very creative and powerful with this!

Until I found dshell, I used to do something similar by using a for loop to execute commands across machines:

for i in `cat servers.txt`; do
ssh root@$i softwareupdate -i -a
done

However, dsh has been thought out much more than the "for-loop-solution" and is much more extendible.

Don't run dsh in your production environment until you read the man page, which details some other options for limiting how many remote machines are accessed at any given time. (Look for the -N and -F options, specifically).

Media of the month: Walt Whitman, The Complete Poems. Start the year off with some poetry - especially if it's not your usual fare. Walt Whitman doesn't do it for you? Check out James Joyce or Emily Dickenson - there are amazing gems in that timeless writing.

Happy New Year!


Ed Marczak is the owner of Radiotope, a technology solution provider. He is also a husband, father and avid wearer of pants. tail -f /dev/brain at http://www.radiotope.com/writing

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Check out the new Pirate Attack update i...
Love pirates and board games? Well, you'll love the new Pirate Attack themed update that just launched in Game of Dice. It adds a bunch of new content themed around pirates, like an all new event map based on a pirate ship which revamps the toll... | Read more »
Splash Cars guide - How to paint the tow...
Splash Cars is an arcade driving game that feels like a hybrid between Dawn of the Plow and Splatoon. In it, you'll need to drive a car around to repaint areas of a town that have lost all of their color. Check out these tips to help you perform... | Read more »
The best video player on mobile
We all know the stock video player on iOS is not particularly convenient, primarily because it asks us to hook a device up to iTunes to sync video in a world that has things like Netflix. [Read more] | Read more »
Four apps to help improve your Super Bow...
Super Bowl Sunday is upon us, and whether you’re a Panthers or a Broncos fan you’re no doubt gearing up for it. [Read more] | Read more »
LooperSonic (Music)
LooperSonic 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: LooperSonic is a multi-track audio looper and recorder that will take your loops to the next level. Use it like a loop pedal to... | Read more »
Space Grunts guide - How to survive
Space Grunts is a fast-paced roguelike from popular iOS developer, Orange Pixel. While it taps into many of the typical roguelike sensibilities, you might still find yourself caught out by a few things. We delved further to find you some helpful... | Read more »
Dreii guide - How to play well with othe...
Dreii is a rather stylish and wonderful puzzle game that’s reminiscent of cooperative games like Journey. If that sounds immensely appealing, then you should immediately get cracking and give it a whirl. We can offer you some tips and tricks on... | Read more »
Kill the Plumber World guide - How to ou...
You already know how to hop around like Mario, but do you know how to defeat him? Those are your marching orders in Kill the Plumber, and it's not always as easy as it looks. Here are some tips to get you started. This is not a seasoned platform... | Read more »
Planar Conquest (Games)
Planar Conquest 1.0 Device: iOS Universal Category: Games Price: $12.99, Version: 1.0 (iTunes) Description: IMPORTANT: Planar Conquest is compatible only with iPad 3 & newer devices, iPhone 5 & newer. It’s NOT compatible with... | Read more »
We talk to Cheetah Mobile about its plan...
Piano Tiles 2 is a fast-paced rhythm action high score chaser out now on iOS and Android. You have to tap a series of black tiles that appear on the screen in time to the music, being careful not to accidentally hit anywhere else. Do that and it's... | Read more »

Price Scanner via MacPrices.net

BookBook For iPad Pro Coming Soon
The iPad Pro is a device unlike any other, and with Apple Pencil, it’s the ideal portable sketchpad: all that’s missing is the modern easel and portfolio to go. TwelveSouth’s BookBook for iPad Pro... Read more
12-inch 1.2GHz Silver Retina MacBook on sale...
B&H Photo has the 12″ 1.2GHz Silver Retina MacBook on sale for $1399 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price for this model from... Read more
iPads on sale at Target: $100 off iPad Air 2,...
Target has WiFi iPad Air 2s and iPad mini 4s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices for... Read more
Target offers Apple Watch for $100 off MSRP
Target has Apple Watches on sale for $100 for a limited time. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - Apple... Read more
Apple refurbished 2014 13-inch Retina MacBook...
Apple has Certified Refurbished 2014 13″ Retina MacBook Pros available for up to $400 off original MSRP, starting at $979. An Apple one-year warranty is included with each model, and shipping is free... Read more
Macs available for up to $300 off MSRP, $20 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Watch Super Bowl 50 Live On Your iPad For Fre...
Watch Super Bowl 50 LIVE on the CBS Sports app for iPad and Apple TV. Get the app and then tune in Sunday, February 7, 2016 at 6:30 PM ET to catch every moment of the big game. The CBS Sports app is... Read more
Two-thirds Of All Smart Watches Shipped In 20...
Apple dominated the smart watch market in 2015, accounting for over 12 million units and two-thirds of all shipments according to Canalys market research analysts’ estimates. Samsung returned to... Read more
12-inch 1.2GHz Retina MacBooks on sale for up...
B&H Photo has 12″ 1.2GHz Retina MacBooks on sale for $180 off MSRP. Shipping is free, and B&H charges NY tax only: - 12″ 1.2GHz Gray Retina MacBook: $1499 $100 off MSRP - 12″ 1.2GHz Silver... Read more
12-inch 1.1GHz Gray Retina MacBook on sale fo...
B&H Photo has the 12″ 1.1GHz Gray Retina MacBook on sale for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Subject Matter Expert - Experis (Uni...
This position is for an Apple Subject Matter Expert to assist in developing the architecture, support and services for integration of Apple devices into the domain. Read more
*Apple* Macintosh OSX - Net2Source Inc. (Uni...
…: * Work Authorization : * Contact Number(Best time to reach you) : Skills : Apple Macintosh OSX Location : New York, New York. Duartion : 6+ Months The associate would Read more
Computer Operations Technician ll - *Apple*...
# Web Announcement** Apple Technical Liaison**The George Mason University, Information Technology Services (ITS), Technology Support Services, Desktop Support Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.