Shell scripting

Shell script wrappers can make the *nix command more transparent to the user. The most common shell scripts are simple wrappers around third party or system binaries. A wrapper is nothing but a shell script that includes a system command or utility.

Linux and Unix like operating system can run both 32bit and 64bit specific versions of applications. You can write a wrapper script that can select and execute correct version on a 32bit or 64bit hardware platform. In cluster environment and High-Performance computing environment you may find 100s of wrapper scripts written in Perl, Shell, and Python to get cluster usage, setting up shared storage, submitting and managing jobs, backups, troubleshooting, invokes commands with specified arguments, sending stdout to stdout and stderr to stderr and much more.

In this post, I will explains how to create a shell wrapper to enhance the basic troubleshooting tool such as ping and host.

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The $ character is used for parameter expansion, and command substitution. You can use it for manipulating and/or expanding variables on demands without using external commands such as sed or awk.

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There are some misconceptions that shell scripts are only for a CLI environment. You can easily use various tools to write GUI and/or network (socket) scripts under KDE or Gnome desktops. Shell scripts can make use of some of the GUI widget (menus, warning boxs, progress bars etc). You can always control the final output, cursor position on screen, various output effects, and so on. With the following tools you can build powerful, interactive, user friendly UNIX / Linux bash shell scripts.

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The Blue Screen of Death (BSoD) is used for the error screen displayed by Microsoft Windows, after encountering a critical system. Linux / UNIX like operating system may get a kernel panic. It is just like BSoD. The BSoD and a kernel panic generated using a Machine Check Exception (MCE). MCE is nothing but feature of AMD / Intel 64 bit systems which is used to detect an unrecoverable hardware problem.

Program such mcelog decodes machine check events (hardware errors) on x86-64 machines running a 64-bit Linux kernel. It should be run regularly as a cron job on any x86-64 Linux system. This is useful for predicting server hardware failure before actual server crash.

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Like most sys admin, I’m lazy. I try to automate almost all things in order to save time. Inexperienced sys admin and help desk staff working under me finds all these tools useful. It saves their time and avoids security issues. Automation allows help desk staff to do things that they don’t have enough direct system knowledge to do themselves. However, selecting correct tool and applying correct methodology is very important.

Note: There is a poll embedded within this post, please visit the site to participate in this post’s poll.

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Is Linux is virus free? The author of foobar blog provides some insight about the same. Linux users can’t just catch a virus by email or downloading malware from the Internet, contrary to “those Windows users”. From the foobar blog post:

Then you save an email attachment under Linux, the execute flag is normally NOT set and thus, the file can’t be executed just by clicking on it. So, no luck?

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