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[one-liner]: Improving the performance of SSH Tunnels using Alternative Ciphers; when displaying X11 Apps

Background

Have you ever used an ssh tunnel to try and remotely display an X windowed application and then wished you hadn’t, because the performance was so bad you’d be waiting till next week for the window to come up?

Read on because here’s how you can make this much more tolerable & usable.

Solution

There are 2 […]

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How to programmatically determine the highest version kernel RPM installed?

Background

Recently on the StackExchange site Unix & Linux the following question came up which seemed easy enough to answer.

How to programmatically determine the highest version kernel RPM installed?

This turned out to be trickier than I originally thought. What follows is my ultimate answer along with several failed attempts. I leave them so that others can […]

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Posted in centos, fedora, package management, rhel, rpm, Syndicated, sysadmin, tip, tutorials | Comments Off on How to programmatically determine the highest version kernel RPM installed?

Why are “executables” such as reboot, shutdown, and vgscan symlinks in the /sbin directory?

Background

If you’ve ever gone poking around in your Linux system’s /sbin directory the site of files like this might make you scratch your head.

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lrwxrwxrwx 1 root root 3 Jun 7 2011 vgmerge -> lvm
lrwxrwxrwx 1 root root 3 Jun […]

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[one-liner]: How to Manipulate an Image Files Modify/Create Date/Time

Background

Recently I answer a question on superuser.com about how to modify the modify/create time/date on an image file such as a TIFF or PSD formatted file.

Solution

There are basically 2 ways to change the modify/create meta data on a file:

From the file-system’s perspective.
Within a file’s metadata.

NOTE: If you’d like to follow along here’s a sample PSD […]

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[one-liner]: Statically building Subversion on Fedora 14

Background

In my experience it can be tricky to compile applications that make use of 3rd party libraries and/or system libraries such as glibc etc. The problem is that in addition to your application being built statically, all these libraries need to provide both a dynamic (.so) version as well as a static version (.a) and […]

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Howto Create a Daily Rotating Log in Perl using Log::Log4Perl

Background

Recently while cruising StackOverflow I came across this question where a user was trying to use the Perl module Log::Log4Perl. Log4Perl provides a mechanism similar to log4j (logging for Java) for logging mesages to various outputs such as the console or a log file. I’ve used this module a couple of times in the past […] Continue reading

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[one-liner]: Using scp to Copy Files that Contain Spaces

Background

Have you ever needed to copy either a single file or a directory that contains spaces using scp? Here are a couple of techniques for how to do this.

Solution

Here are several ways to accomplish the same thing. Copying a entire directory with spaces and copying a file with spaces using scp.

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# Ways to copy entire […] Continue reading

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CentOS RPM Tutorial Part 4 – Another Example of Rolling your Own .spec File

Getting Started

In this 4th installment of my series on RPM packages I’m going to show another example where I package up a tarball that I’ve created, and roll it into an RPM file. For this example I’ll be packaging up a Perl script and a man page. NOTE: Refer to my previous posts (part 1, […] Continue reading

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Example Bash Script which Monitors if a Program has Died, and Restarts it

Background

Here’s a quick script that might prove useful if you need to watch if a program is running and restart it if it stops for whatever reason. It is by no means fault tolerant, but could be adapted to be more so if needed.

Solution

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#!/bin/bash
 
# NAME: check_dropbox.bash
# DESC: watch if dropbox is running
 
check_process() {
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[one-liner]: Commenting out a block in an XML file using sed

Background

This issue came up recently where I needed to programmatically comment out a section of tags in an XML file.

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<login-module code="org.dcm4chex.archive.security.TrustLoginModule"
flag = "required" >
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