[wplug-announce] The Open Pitt, Issue 34

Vance Kochenderfer vkochend at nyx.net
Mon Apr 30 23:47:23 EDT 2007


PDF version: <http://www.wplug.org/top/wplug-top034.pdf>

                               THE OPEN PITT
      What's cooking in Linux and Open Source in Western Pennsylvania

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Issue 34                        April 2007                    www.wplug.org
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In this issue:
  Book Review: Spring Into Linux
  System Monitoring with dstat
  March Roundup

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Book Review: Spring Into Linux
by Bobbie Lynn Eicher

  Author: Janet Valade
  Publisher: Addison-Wesley Professional
  ISBN: 0-13-185354-6
  $29.99, 336 pages, 2005

The "Spring Into..." series of books
<http://www.awprofessional.com/springinto/> is designed with the goal of
bringing people up to speed quickly on various technological topics.  As
part of that mission, each entry in the series focuses on allowing
experienced professionals to pick up and work with new topics quickly.
Each specific topic takes up at most a few pages, which helps to hold the
level of detail down to the most crucial elements.

On the whole, Janet Valade's effort at providing a basic introduction is
solidly designed and executed.  Each chapter includes an introduction at
the beginning and a summary at the end, making it easier for readers to see
where the current topic fits into context and decide whether a particular
chapter covers a topic they need.  Most topics are covered in a single
page, expanding to two pages when necessary.

The layout of the text consistently favors clarity and ease of locating
topics as needed.  While they could possibly have saved a few pages by
trying to cram more material onto each, instead each new topic presented
begins at the top of a new page, clearly labeled with a header that makes
the subject clear, rather than requiring readers to skim through and get a
sense of it themselves.  If something is mentioned briefly but described
more completely elsewhere, the author makes it immediately clear where to
turn for a more detailed explanation, saving readers the hassle of
searching through the table of contents and index.

It's fortunate that the layout is so excellent, because the ordering of
chapters and topics is sometimes strange.  Considering that most users new
to an operating system are eager to get a look at the programs for daily
tasks, it's odd that this discussion is delayed until after coverage of
topics like the command line and changing file permissions.  Likewise,
teaching the use of the command line prior to explaining what the root
account is and why it should be avoided by novices seems like a careless
oversight.

Though the writing and tone are clear in general, there's occasional
inconsistency about the assumed skill of the reader and a few important
details slip by.  The descriptions of how to use applications are more
basic than the skills expected in areas such as the use of the command
line, though this may be based on assumptions about which readers will be
interested in those chapters.  Also, while she only covers the use of the
bash shell, the author never actually makes it clear how to check which
shell you're in, which could easily confuse users who happen to find
themselves at a terminal with a different shell active.

It may suffer from a few imperfections, but the sheer ease of navigation
makes _Spring into Linux_ an excellent book for professionals seeking a
concise guide to using their new operating system.

Bobbie Lynn Eicher is a long-time member of WPLUG and holds a B.S. in
Computer Science from the University of Pittsburgh.

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System Monitoring with dstat
by Patrick Wagstrom

If you've been around Linux for a while, you're almost certainly familiar
with the venerable top program--a system monitor that provides an ever-
updating glance of what's going on in your system.  When a system is
behaving poorly, top will show you the load numbers.  However, do you
really know what they mean?  If you answered "the sum of the number of
processes in the run queue and those currently executing averaged over 1,
5, and 15 minutes," you'd be correct.  For a single-processor system, if
the load is greater than 1, it usually means that your system has more work
than it can perform at the current moment.

However, the increase in speed of CPUs over the past decade has far
outpaced the increase in speed of hard disks and memory.  Today you may
have a system that claims to be heavily loaded, but in reality the
processor is mostly idle.  Where is the holdup in the system then?  We
could look around the /proc filesystem or use tools like vmstat, iostat,
and netstat for more information, but wouldn't it be nice if all the
information you needed were available with one program?  That's exactly
what dstat does.

To start out with dstat, download it from
<http://dag.wieers.com/home-made/dstat/>.  Try running it without any
options at the command line.  As shown in the example output below, you'll
see five sets of information--CPU usage, disk activity, network activity,
memory activity, and system activity.

                            Sample dstat Output
  ----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system--
  usr sys idl wai hiq siq|_read _writ|_recv _send|__in_ _out_|_int_ _csw_
   21   4  73   1   0   1|  30k   43k|   0     0 |2143B 3846B| 218   553
    6   2  92   0   0   0|   0   256k|2546B    0 |   0     0 | 350   597
    7   0  92   0   0   1|   0     0 |2546B    0 |   0     0 | 344   450
    7   1  92   0   0   0|   0     0 |3084B  284B|   0     0 | 326   483
    6   0  94   0   0   0|   0     0 |3288B 1188B|   0     0 | 370   569

Unlike top, the details of CPU usage are given in six columns.  The column
headed "usr" shows the percentage of time taken by user processes.  System
processor usage by the kernel is indicated by "sys," and "idl" is the
percentage of time the CPU is sitting idle.  Wait time is marked "wai" and
shows the time tasks are waiting for I/O, such as hard disk activity, to
complete.  Expect to see degraded performance if this value is high.  Time
spent processing hardware and software interrupts is indicated by "hiq" and
"siq."  These statistics are averaged over all processors in the system;
luckily, you can select which processors to display information for by
using the -C flag.

Next up is disk information.  By default, this is the total disk I/O across
the entire system.  For systems with multiple disks, you'll find the -D
option to split up disks useful.  If you use software RAID or LVM, you can
even view individual disks or partitions within the group.

After disk information comes network usage.  Similar to the other
statistics, this can be broken up by interface with the -N option, which is
quite helpful when running a network firewall with multiple devices.

The final two default groups are slightly more esoteric, but useful
indicators of system performance.  Paging refers to the process of moving
data into and out of RAM.  For example, when an executable is loaded there
will be movement of code from disk into memory.  When memory is nearly
full, data must be paged out to disk.  While some paging is inevitable, too
much will bog down your system.

Finally, the system grouping has "int," the number of interrupts processed
since the last update.  These are caused by a number of different devices
such as hard drives, network cards, Firewire devices, or the internal
timer.  They do exactly what the name says; they interrupt the current
execution and jump to code to handle the event in question.  Too many may
cause a high number of context switches, which is what "csw" stands for.  A
context switch occurs when the CPU switches from one task to another.  Just
like a human being switching tasks, this takes a small amount of time.  Add
up too many, and you can have a problem.

In addition to the built-in features, dstat has a plugin interface that
makes it fairly easy to add modules covering other statistics.  Under
Ubuntu, dstat comes with modules for WiFi properties, CPU frequency,
thermal properties, and a whole slew more.  While it may not give as much
detail as some of the other tools available, together with its plugins it
provides a nice and fast way to get an overview of the system and is a
valuable part of any system administrator's toolbox.

Patrick Wagstrom is a Ph.D. candidate at Carnegie Mellon University
researching communication and collaboration in Open Source development.  He
has been using Linux since 1994.

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March Roundup

Mar. 10 General User Meeting: The theme for this meeting was "How do I do
that?" with demos of ways to perform common tasks under Linux.  Patrick
Wagstrom tackled the issue of managing your digital photos.  He showed how
you can import them from your camera, edit, organize, and publish them
online using F-Spot or Google's Picasa.  Patrick also demonstrated how to
handle multiple users on the same machine using GNOME's Fast User Switching
applet as well as the more traditional display manager login.  Office tasks
were covered by Vance Kochenderfer, who showed the basics of how to lay out
a newsletter in the OpenOffice.org word processor and a brochure with the
Scribus desktop publishing application.  He capped this off with a demo of
some abilities of Konqueror, KDE's web browser/file manager/kitchen sink,
such as ripping audio CDs, extracting and creating ZIP files, and securely
transferring files over a network.

===========================================================================
The Open Pitt is published by the Western Pennsylvania Linux Users Group
<http://www.wplug.org/top/>

Editor: Vance Kochenderfer

Copyright 2007 Western Pennsylvania Linux Users Group.  Any article in
this newsletter may be reprinted elsewhere in any medium, provided it is
not changed and attribution is given to the author and WPLUG.


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