Sandra Henry-Stocker

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  • Graphing system activity with SAG

    Posted June 19, 2008 - 10:09 am

    Here's a script that turns sar data into useful little performance graphs using sag, the system activity grapher. The sag utility reads data from sar's binary files and, provided with a graphical terminal, creates a line chart showing CPU usage or some other sar data.
  • Changing IP addresses on Linux systems

    Posted June 11, 2008 - 1:25 pm

    Changing the IP address on a Linux system involves both changing the IP address using the ifconfig command and modifying the files that will make your change permanent. The process is very similar to the process you would follow on a Solaris system, except that a different set of files must be modified. The proper steps to take also depend on the particular Linux distribution you are using. Debian systems, for example, use different files to store network configuration than do RedHat systems.
  • Unix tip: Using sar for long-term performance analysis

    Posted June 4, 2008 - 4:08 pm

    The sar command, native to Solaris and often installed on Linux systems via the sysstat package, is extremely useful in analyzing current and recent system performance. On the other hand, if you would like to view performance on your servers over a long time span (more than a month), you need to take some extra steps to preserve your data.
  • Green Computing Summit 2008: Going green is no longer optional

    Posted May 23, 2008 - 3:33 pm

    According to EPA, corporate and governmental data centers in metropolitain areas are already driving the power grid toward gridlock. By 2010, we could have 41 million servers in the US, with less than 10% utilization. Power consumption in data centers in the US could cost $7.4 billion by 2011, compared to $4.5 billion today. How did we get here?
  • Removing robots from your web traffic analysis

    Posted May 22, 2008 - 10:12 pm

    Advice on robots, and removing bad traffic
  • Unix tip: ZFS administration

    Posted May 12, 2008 - 11:53 am

    ZFS is without doubt a giant step forward in file system design and is without practical limitations. It features an impressive immunity to the kind of file system corruption that have hounded many of us for decades (refer to my recent problems with "freeing free blocks" crashes). Created by Jeff Bonwick's team at Sun, ZFS is already in use on various Linux, Mac OS X and FreeBSD systems.
  • The Sun system life cycle

    Posted May 8, 2008 - 3:50 pm

    will have been assigned a predictable end date.

  • Unix tip: Rescuing files from lost+found

    Posted May 6, 2008 - 10:23 am

    them to look rather unusual. Take these files found on a Solaris 9 system after a panic and a subsequent fsck.

  • Unix Tip: Using SCAT (Solaris CAT) for analyzing crash dumps

    Posted April 23, 2008 - 1:20 pm

    Want to do something with those crash dump files other than remove them? Want to extract some useful information without a lot of work? Take a look at Sun's free crash analysis tool, scat.
  • Unix sleuthing: One problem leads to another

    Posted April 18, 2008 - 4:49 pm

    When tracking down an unusual problem on a Unix system, you may encounter many turns and dead ends on the path toward the solution as some problems may have little connection to what first appears to be troubling your system. We're going to follow an unusually winding path from first appearance of a problem to its eventual solution.
  • Dot What!? sites for file extensions

    Posted April 11, 2008 - 11:12 am

    Dot What!? offers visitors an opportunity to suggest additional file extensions and to add comments concerning their uses and associations.
  • Book Review-- Hacking: The Art of Exploitation, 2nd Edition

    Posted April 2, 2008 - 2:01 pm

    Read it if you want a thorough understanding of various hacking techniques, especially if you know enough about programming to put some of what you learn into practice -- not for hacking (we hope), but to use the same skills for vulnerability testing and the same knowledge for protecting your network.
  • Unix Tip: Terminating unattended processes

    Posted March 26, 2008 - 3:59 pm

    A reader recently asked how he could most easily terminate processes that were left running after his users had logged off a system. The processes in question were apparently consuming resources needed by other services and were not contributing to any particular project. What he was looking for, however, was a solution that would not require him to detect the processes and manually terminate them, even if commands such as "pkill -u username" might simplify the job.
  • Unix Tip: More on bc

    Posted March 20, 2008 - 10:25 am

    The bc utility is not just acommand line tool. You can also write numerically intensive scripts in bc. The tool incorporates enough syntax to assign values to variables, write and call functions, collect responses from users and print annotated results.
  • Unix Tip: Using bc for big calculations

    Posted March 12, 2008 - 6:44 pm

    For sysadmins who want to perform simple calculations on the command line, there's a considerably more useful tool than expr. Try bc. Like expr, the bc command allows you to do simple math.
  • Unix Tip: Burning bootable DVDs

    Posted March 5, 2008 - 9:43 pm

    One of the messages that you don't want to see when getting ready to upgrade a system to Solaris 10 is "can't open boot device". The problems this kind of error suggests, such as bad CD/DVD reader or improper device alias, can be troublesome. So, when I ran into this problem on a Friday afternoon, I was not amused. I had tried various boot commands, but got the same basic response each time...
  • Unix Tip: Terminating options processing with --

    Posted February 26, 2008 - 1:23 pm

    To understand how this works, think back to how the shell processes what it sees on the command line. If we type "ls -l a*", for example, the shell translates a* into a list of all files that begin with the letter "a" and then makes the appropriate system calls to provide a detailed listing of those files, complete with owners, sizes and most recently changed dates and times.
  • Unix Tip: More on filenames

    Posted February 20, 2008 - 10:53 am

    of Unix (e.g., Solaris).

  • Unix Tip: Stripping file extensions with the basename command

    Posted February 11, 2008 - 8:55 pm

    I recently discovered a new trick for using basename to extract filenames from a full pathnames.
  • Unix Tip: How-to rename an oddball file

    Posted February 6, 2008 - 12:02 pm

    Every now and then I come across a file that just doesn't display properly in a file listing. In fact, it can be a little tricky to determine the name of a file that contains odd characters. You might think a file's name is "myfile.txt" only to find out that it's really "myfile.txt " (note the extra blanks). Here's a way to name a file with an odd name.
  • Unix Tip: Reassembling very large "split" files

    Posted January 30, 2008 - 6:38 pm

    One of the unwritten rules of computing says that, as various storage media grow in size, so do the files that are written to them. I recently found myself staring at two files, each roughly 4 GB in size, that needed to be combined into one before the file could be decompressed and its contents extracted. What I was expecting to work with was a large cpio archive. I had loaded each of the file components from a DVD, thus the reason that the file had to be compressed and then broken into two pieces, each of which could be written to a DVD.
  • Unix Tip: Experimenting with rsync

    Posted January 23, 2008 - 1:42 pm

    This article shows how to create a directory with a number of files, copy the directory with an assortment of rsync (and other) commands, take a closer look at some of rsync's command options and then use rsync to verify that the replicated directory is intact.
  • Unix Tip: Shuffling file systems with rsync

    Posted January 16, 2008 - 1:19 pm

    Here's a tool that copies my files and verifies that the files made it to their new destination intact -- rsync.
  • Unix Tip: Local message processing with syslog

    Posted January 8, 2008 - 3:04 pm

    The syslog deamon (syslogd) on Unix systems provides message logging for other services so that each service doesn't have to duplicate the same basic functionality to manage logging for itself. The messages issued and their severity level depends on the applications, but where these messages are logged and how they are filtered when using the services of syslogd depends on how syslog is configured. The basic format of a line in syslog's configuration file specifies a message type and how messages matching the type will be handled.
  • Book Review: The Glossary of Digital Photography

    Posted January 4, 2008 - 2:42 pm

    Anyone seriously interested in digital photography would be foolish not to pick up a copy of this book.
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