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. 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…
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