Linux Server Hacks, Volume Two

Hack #80. Keep a Constant Watch on Hosts

Monitor load or other statistics for multiple hosts on your desktop or on the command line.

rstatd is an RPC-based kernel statistics server that is either included with or available for every form of Unix I've ever used. It isn't something new. In fact, I suspect that its age might cause it to slip under the radar of younger admins, who might not know it if it hasn't appeared on the front page of Freshmeat recently. Hopefully, the information here will pique your interest in this very useful tool.

When I say that rstatd provides "kernel statistics," I'm referring to things such as CPU load, page swapping statistics, network IO statistics, and the like. Of course, providing this information to administrators in a way that is useful can sometimes be challenging, but there are a few tools available to help.

To make these tools useful, you must have a running rstatd daemon. Note that rstatd is dependent on the portmap daemon, which should already be running if you're using other RPC-based services such as NIS or NFS. To do a quick check to make sure these are running, you can run the following command:

$ rpcinfo –p
				program	  vers   proto   port
				100000		2	   tcp	  111 portmapper
				100000		2	   udp	  111 portmapper
				100001		3	   udp	  646 rstatd
				100001	    2      udp    646 rstatd
				100001      1      udp    646 rstatd

Without any other arguments, this will show you the status of the local host. If you put a hostname on the end of the above command, it will show you the status of a remote host. Now ...