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Changing When Daily Cron Jobs Run in Ubuntu

by Chris Jean

March 18th, 2009

Linux has many great tools built in that help maintain the system without user intervention. One such tool is Cron.

On my Ubuntu 8.10 system, there are many things that are set to run each day: locate database updates, misc cleanup utilities, automatic package updates, log rotations, etc. All of these are managed by the Cron system.

For a while, I needed to manually run the updatedb command to update the locate database, and I never thought about why. The problem is that my daily, weekly, and monthly Cron jobs never run. The reason for this is that these Cron jobs are scheduled to run very early in the morning, when my system is off. Thus, these job schedules never run.

The solution for this is easy. I simply need to change the times these run at to times when my system is on.

Categories Linux, Tips 'n Tricks
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Command Line History in Ubuntu Terminal

by Chris Jean

March 9th, 2009

I’ve had a lot of fun recently posting about how to do stuff on the command line in Linux. My focus is specifically for Ubuntu users, but the information and techniques can be used for any Linux distro.

Since I’m probably going to end up with a lot of content under this topic, I’ve decided to create a dedicated tag: Mastering the Command Line. I’ve gone through my older posts on this topic and tagged them as well. So, make sure to check out Mastering the Command Line if you want to know how to become a command line power user.

Back to today’s topic. You’re starting to learn how to use the command line, but it’s annoying to always have to type in similar commands over and over. If only there were a way to pull up commands that you’ve already run to run again as is or to quickly modify. Today, I’m going to teach you how to do exactly this.

Categories Linux, Tips 'n Tricks
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Convert DOS-Formatted Files to Unix-Format in Ubuntu and CentOS

by Chris Jean

March 8th, 2009

Have you ever seen a bunch of ^M characters in a text file? This odd character at the end of a line can also be represented as a Ctrl+M or <CTRL>M. You don’t know what it is, and you want it to go away.

Today, I’ll help you understand what that odd ^M character is, why it is in some of your documents, and how to get rid of them.

Categories Development, Linux, Tips 'n Tricks
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Cleaning Out Old Linux Kernels in Ubuntu

by Chris Jean

March 5th, 2009

Without the Linux kernel, Ubuntu (and all the other Linux distros) would not exist. Despite this, most Linux users don’t know what a kernel is nor understand that the reason that Ubuntu is a Linux distro is because the kernel is Linux. All most users of any Linux distro is likely to know is that they will eventually have a large number of kernels installed on their system cluttering up their boot menu.

Describing what a kernel is and what it does is beyond the scope of this post. I do highly recommend that you first read the Wikipedia article on computer kernels followed by the article on the Linux kernel itself. I’d really like to do a post explaining what a kernel is in simple terms so that readers can gain a better appreciation for it and what it does for your distro. Please leave a comment letting me know if you are interested in this writeup.

Anyways, back to the topic at hand. What do we do with all these kernels that litter our boot menu? How do we remove them not just from our boot menu but from our file system as well?

Categories Linux, Tips 'n Tricks
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4 Great Tools to Find Files Quickly in Ubuntu

by Chris Jean

March 4th, 2009

Many of you fellow Ubuntu users will be familiar with the “Search for Files” tool that allows you to look for files. As is true with most things in Linux, there are great desktop tools, but more power can be found in Terminal than any streamlined desktop tool can match.

Today, I’d like to introduce you to a few tools that can turn a chore of finding files into an easy process.

Categories Linux, Tips 'n Tricks
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Multiple Firefox Profiles in Ubuntu

by Chris Jean

February 23rd, 2009

When Windows was my main OS, I was a big fan of Portable Firefox. With Portable Firefox, I could do multiple installations of Firefox on my system that could be customized to run concurrently with other installs of Firefox. This allowed me to have tailored installations with different sets of plugins and features.

Why would I want to run more than one Firefox at a time? For me, the reason is that it eases development. Here are a few ways that I use multiple installs:

One install that was just the default install with no additional tweaks or add-ons and would have all cached data, authenticated sessions, and cookies cleared when closed. This was a great browser to use when I would test new code to make sure that it ran well on a stock Firefox. It also gave me a clean cookie and authentication slate so I could test sessions from scrath without clearing my main browser’s history, sessions, etc. If I wiped the slate clean on this browser, nothing was lost.
Since having a large variety of add-ons in Firefox has a tendency to slow things down, I had another browser that included all the major development tool add-ons. I would load this browser up when I needed to explore the DOM in detail, debug layout issues, debug Javascript, etc. This allowed me to streamline my main browser down to just the add-ons that I use frequently.
Since Portable Firefox isn’t installed and just resides in its own folder, I could load multiple versions of Firefox. This made it easy to test for compatibility problems between different versions.
I even played around with the idea of having a browser specifically for media. I would use it for music sources like Pandora and for video sources like Hulu or Red vs. Blue.

Last week, I looked around for a solution like Portable Firefox for Ubuntu. I quickly found a solution that wasn’t nearly as difficult as doing multiple installs: multiple profiles.

Categories Linux, Tips 'n Tricks
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Showing/Hiding Hidden Files in Nautilus

by Chris Jean

February 22nd, 2009

Today’s post is just going to be a quick tip since I just finished sitting in the car for about four hours. I spent most of the day with John P, Mrs. P, Cali Lewis, and many other fun people at the AMC Best Picture Showcase at the Northpark AMC in Dallas. Since I live in Oklahoma City, I had to do a bit of driving.

None-the-less, it was a ton of fun. I got to see some movies, get a change of scenery, meet some new people, and even got live video blogged. Anyways, on to the important stuff.

One neat trick I found out about recently when working with Nautilus is how to quickly show and hide hidden files (files or folders that begin with a dot). Simply hit Ctrl+h and the display of hidden files will be toggled. This is great to quickly gain access to hidden folders that you don’t care to type in manually.

Not only does this work in the Nautilus File Browser, but it also works in any file dialog that uses Nautilus. So, next time you are in a save or open file dialog, hit Ctrl+h to show/hide the hidden files and folders. I find this very useful in Gimp which insists on showing me all the hidden stuff by default.

Categories Linux, Random Ramblings, Tips 'n Tricks
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Proper Adobe Flash Support on Ubuntu 64-bit

by Chris Jean

February 20th, 2009

In one of my earlier posts, I talked about setting up Ubuntu 64-bit on my Dell Studio 17 laptop. I provided some information on how I set up Flash on my system. This solution used the 32-bit release version of Adobe’s Flash plugin and nspluginwrapper to allow the 32-bit plugin to be used with the 64-bit version of Firefox. I had just a few problems with this solution:

Google Analytics would crash the entire browser if I tried to change the date range.
Hulu would always take at least a minute to load any video. Full length videos would sometimes take as long as five minutes to load.
Youtube would often times not work correctly.
Random parts of certain Flash applications would not work at all.
The new Hearts of Space Flash player didn’t work.
All too often, all Flash apps would fail. This resulted in every instance of Flash being replaced with a light-gray background.

Fortunately, I found a great solution to this problem: an actual 64-bit Adobe Flash Plugin.

Categories Development, Linux, Tips 'n Tricks
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SSH Tutorial for Ubuntu Linux

by Chris Jean

February 19th, 2009

I touched on this topic in my First Day with Ubuntu at the Office post under Accessing Remove File Systems; however, I thought that this deserved its own topic.

For those that don’t know SSH stands for Secure SHell. In very non-technical terms, SSH allows you to access a system running a SSH server over a network. This other system can be another computer in your home or a remote system on the other side of the planet. SSH will allow you to connect to that other system and communicate with it securely. All the data passed back and forth is encrypted, so you don’t have to worry about people sniffing your passwords or valuable data.

You may be asking what all of that means to you. What it means is that you can connect to and control a computer that is somewhere else with the computer that is sitting right in front of you. If you have a remote webserver running Linux, SSH will let you install software, edit files, change the server configuration, access the database, and more. Did you forget a file on your computer at home? No problem, just SSH into your home computer and send the file to your email account or copy it directly to your office computer.

Hopefully those quick examples of what you can do is enough to whet your appetite.

Categories Development, Linux, Tips 'n Tricks
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Easily View Images From Terminal in Ubuntu

by Chris Jean

February 17th, 2009

I have a quick Ubuntu tip for you today. You’re on the command line and have an image in the directory that you’re currently in. How can you easily view this image without loading Nautilus, browsing to the directory, and opening it from there? It turns out that the answer is very simple.

The default image viewer in Ubuntu is called Eye of Gnome. Using Eye of Gnome, you can quickly view the following images: ani, bmp, gif, ico, jpeg, pcx, png, pnm, ras, svg, tga, tiff, wbmp, xbm, and xpm.

To run Eye of Gnome from the command line, simply run “eog”. So, if you have a file called image.jpg in your current directory, you can simply run the following to view it:

eog image.jpg

Now you never again have to wonder what that image is as you’re browsing around in Terminal.

This tip will work for any distro running Gnome, such as Linux Mint.

Categories Linux, Tips 'n Tricks
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