I've just found an interesting article at Linux Magazine
http://www.linux-mag.com/id/3926/
You'll need to register and login to view it, so I'm pasting it here.
I'm not sure, but it really sounds Capistran-ish to me =)) [somebody
should talk to Jeremy about covering Capistrano if they haven't, and
plead that they will use a little bit more involved example :)]
Remote Administration with DSH
Thursday, August 2nd, 2007By Jeremy Garcia
<http://www.linux-mag.com/author/55>
Previous "Tech Support" columns introduced both Perlbal and Pound,
two packages to load balance traffic across multiple machines.
Dividing load among several servers provides better performance and
increased reliability. However, more machines translates to more
tedium. Previously simple actions --- such as restarting a service
--- becomes complex.
There are multiple solutions to managing a collection of machines.
One common solution is to write a custom script for each task. A
more innovative solution is dsh, the "distributed shell." dsh is a
wrapper implementation to execute remote shell commands on multiple
machines. dsh abstracts the problem of multiple machines and offers
a general solution.
dsh is provided under the terms of the GNU Public License and can be
downloaded from the dsh home page at
http://www.netfort.gr.jp/~dancer/software/dsh.html.en
<http://www.netfort.gr.jp/%7Edancer/software/dsh.html.en>. Before
you install, download, build, and install libdshconfig, which is
also available from the dsh home page.
To build and install dsh, run the standard commands:
$ ./configure
$ make
$ sudo make install
dsh has three system-wide configuration files, and you can extend
those with personal settings.
*/usr/local/etc/machines.list and $HOME /.dsh/machines.list
enumerate the machines to operate upon if the --a ("all machines")
option is specified.
*/usr/local/etc/group/ groupname and $HOME /.dsh/group/ groupname
define the group named groupname. To operate on a group of machines,
specify --g groupname.
*/usr/local/etc/dsh.conf and $HOME/.dsh/dsh.conf set parameters for dsh.
man dsh.conf describes all of the available configuration options.
Both the machines.list and the dsh group files are a list of
machines, one machine name per line.
For the best security, always set remoteshell=ssh and ensure that
SSH keys provide ready and automatic access between all of the
machines. Depending on your environment, the remoteshellopt option
can also be extremely useful. You can use remoteshellopt to specify
an alternate port number if your machines do not run SSH on port 22.
You're now ready to use dsh. To get the output of the w command from
all of the machines listed in machines.list, run:
$ dsh --a w
If you'd like the name of the machine prepended to the output, add
the --M option, as in dsh --M --a w.
While it should immediately be clear how useful dsh can be in a
distributed environment, the machine group feature really increases
the utility's flexibility. You can create a distinct group for your
Web cluster, another for your database cluster, and yet another for
your compute servers. Machines can be grouped arbitrarily to let you
execute commands on a subset of your infrastructure.
For example, if you create a Web group, you can restart Apache on
all machines with:
$ sudo dsh --g web '/usr/local/apache/bin/apachectl restart'
You can execute commands in a more ad-hoc fashion with --m
(lowercase). For instance, the next command runs last on the
machines test1 and production1:
$ dsh --m test1 --m production1 last
You can even point dsh to an arbitrary file with a list of machines
names with the --f flag. As you can see, while dsh is very
simplistic, it was built with flexibility in mind.
Finally, if you're concerned about overwhelming your machinery with
commands or want to progress more slowly, try --F to limit the
number of concurrent commands. In most cases, you can ignore such a
governor, but if you use dsh on a huge number of machines, it's a
good idea to set the limit somewhere between 100 and 200.
dsh is a simple mechanism to execute the same command on any number
of remote machines. Its group feature makes it flexible enough for
almost any environment.
Jeremy Garcia <http://www.linux-mag.com/author/55> is the founder
and administrator of LinuxQuestions.org, a free, friendly, and
active Linux community that filters its email with SpamAssassin.
Please send questions and feedback to [EMAIL PROTECTED]
--
Hendy Irawan
www.hendyirawan.com
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