An article on Lifehacker featured an interesting utility called iotop, which gives a birds eye view of what your hard drive is up to. The commentors mentioned a couple of other interesting tools, although many seemed to be confused as to what iotop is measuring as opposed to some of the other utilities. I thought I'd do a quick write up about a few of these command line machine status reporters.
The most basic status tool is, of course, ps. In number of options, it competes with ls for most in the Linux manual! This is because it has 3 different command "modes" - UNIX, BSD and GNU versions, and all are usually mutually incompatible. ps gives you a basic snapshot of what programs are being run.
While ps is always around, the rest of these usually need special installation, although the next one, top, is almost always around. top adds more information but, most importantly, runs in a curses display, so it stays around and updates itself, giving you a constant view of what your CPU is up to. You can see it change dynamically as programs work your CPU harder. Use the 'h' key to display a help screen, giving you more sorting and display options.
The most flexible version of ps is htop. This gives you even more information, more sorting options and an even better curses display. Again, use the 'h' command to get a full help display. I especially like htop for how it displays the complete command line.
iftop uses a top-like display to show you what is going on in your network (your interface). It displays the various network requests, who is making them and how much is coming and going on each. This is an especially useful command on a server, as you can see what your web server is working on, and keep useful totals.
iotop again uses a top-like display to give you a real time, in-depth view of disk I/O. This is an especially useful diagnostic tool if you notice your hard disk is "thrashing" - ie, the red access light is doing a disco-like strobe effect and you're wondering who is doing all that hard drive dancing.
saidar is another monitoring tool that shows a nice overview of everything going on in your computer. Useful information like CPU load, swap usage, disk space, and network traffic. Good quick clean overview.
Next time, perhaps I'll take a look at some of the graphical system monitoring tools available for KDE and GNOME. If you have any other favorite terminal-based monitors, please mention them in the comments.
