Here’s a cool program that can be pretty helpful: htop (http://htop.sourceforge.net/).
Monitoring the vital stats on a Linux server can be difficult; you’ve got a ton of utilities like top, free, /proc, vmstat, sar, al
ong with logs to sort through. Imagine if on Linux you could watch each process, view its threads and sub processes, track memory usage and sort your entire systems performance by whatever variables you desired? This is possible and much more with htop.
Htop calls itself “an interactive process viewer for Linux” that runs from the console as an ncurses-built application. Once you load it, right away you’ll notice some considerable improvements over the standard top. The use of ncurses gives htop visually pleasing and functional text-based graphical interface. Along the top of the screen you’ve got color coded bars:
- CPU usage, color coded to show cpu time by normal, kernel, irq, and io-wait usage
- Memory usage, color coded to show actual usage vs. cached and buffer usage–a huge timesaver instead of trying to interpret the output of vmstat or free!
- Uptime and load averages.
The process list in htop is also vastly improved. You can scroll through it (arrow keys), view it in tree mode (F5) to show links between threads spawned by a process, sort by columns (F6) any of the defined metrics, search for keywords (F3), change nice level (F7,F8) or even interactively kill a specific process (F9).
Enter setup (F2) and you’ll find that everything about the main window is customizable. You can display as little or as much information as you want it to. You can also change the style of or add additional meters to the top, as well as change the default color coding. The columns in the main part of the display are also entirely customizable allowing you to choose from a wide variety of available system monitors and resource counters.
The best part about htop is that is easy to use and understand, even a novice can get a look at what’s going on under the hood of their machine, but it’s still powerful enough to use as a serious timesaving device for the advanced user. Once you get in the habit of using htop, it’s something you’ll want to have at your fingertips at all times.
Red Hat recently released the latest version of their Linux distribution: Red Hat Enterprise Linux 6 (RHEL 6). This is exciting because of the approach Red Hat takes with their Enterprise Linux. They stress stability and reliability over cutting edge features. One way they do this is to lock in to particular versions of software that they provide.
For example, with RHEL 5 they locked to a recent, well-tested version of PHP (5.1.6). During the life the RHEL 5 this has not changed even as newer versions of PHP came out sporting nifty new features (they did add security and bug fixes, however). This meant that you could set up your website on RHEL 5 server and not worry that an update would be released that added (or removed) a feature that changed the way your site behaved. The downside is of course that new features were not available if you wished to take advantage them. Many PHP applications (such as Wordpress) began to require features not available in the RHEL 5 PHP. RHEL 6 locks to much more recent versions of software, allowing you to get new features but retain the benefits of Red Hat’s thorough testing and updating process.
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The PS, or process status, command is available in the default tool-set on almost all Linux, BSD and other UNIX like operating systems. Like the task manager or process explorer on Windows it can provide a wealth of information about all of the processes running on your system while allowing for very fine control over sorting and filtering the results.
‘PS is one of those commands that you may use often, however never tap into the true flexibility of it. If you haven’t used it, PS displays a list of the current processes running on the system at the time you run it. PS supports a large number of options can be used to modify or extend its output. For instance, one of the most common uses of PS is to list in detail all the processes running on the system at the time the command is run, like this:
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Spend a little time working through PCI DSS and you quickly realize that much of the focus is on understanding and reducing risk. This often means efforting to keep sensitive info on a need-to-know. Here are just a few ways you can improve your Linux security:
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Two weeks ago while attending LISA (the Large Installation System Administration conference), I heard many times that open source software is the way to go; after all, “you can’t beat free”. During one of the classes, someone from a university IT department pointed out that open source software is “free like a free puppy”. To the bemusement of the attendees, he explained his point. A free puppy still comes with costs –training, shots, food, etc.
Most IT decision makers understand that “free” software really isn’t free, so what factors go into the decision to use open source software over something proprietary?
Numerous surveys have been done to try and determine why someone would choose open source software. Surprisingly, few people rank cost as the number one reason (this figure varies, but is often around one in five). Although the software comes with no initial upfront fee, it still needs to be supported and maintained. Factors like staff training can add significantly to the cost of supporting a platform, as can the need to develop management tools that integrate into the infrastructure. Vendors, like Red Hat, offer training programs and certifications to help companies find staff with the necessary skills. Red Hat also offers tools to help manage an enterprise built on their flavor of Linux, along with their own technical support. None of these options are free, even though the core operating system is open source.
That said, one area where lower costs can be seen is in scalability. Once you have the staff at your disposal, you can rapidly scale out an open source platform without additional license fees (assuming you go with a truly free OS). Proprietary software (such as Windows) comes with a per-instance cost that grows with your server population. This is also true for a “supported” open source OS like Red Hat.
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