One usually would install pdsh from homebrew but for some reason the groups file support was removed from the homebrew pdsh version some time ago. The groups file feature is pretty essential for pdsh usage.
You can do the following to install pdsh manually.
git clone firstname.lastname@example.org:chaos/pdsh.git
brew install autoconf automake libtool readline
fix libreadline discovery
Help the compiler to find libreadline with:
modify bootstrap script
For compat reasons libtoolize is named glibtoolize on mac OS. You need to adopt this in the `./bootstrap` script.
prepare project build config
configure project with groups support
./configure --with-ssh --without-rsh --with-nodeupdown --with-readline --without-xcpu --with-dshgroups