Why?

Why continue to break out more command line tips? Simple. Although it is very possible to get through the day (maybe even your entire Linux lifetime) without dropping to the command line, there are times when the command line is the best tool for the job. And knowing the command line in Linux is knowing power. So…let’s put some power at our fingertips.

Uptime

I had a friend once that had a Linux box with an uptime of over three years. THREE YEARS! The box finally came down because a NIC went bad and he had to shut it down to replace it. It broke his heart. Every day he would send me his uptime and we would both “oooh and ahhh” over it. How did he do this? The uptime command. This command does one thing and it does it well – it tells you how long your machine has been running. You issue this command like so:

uptime

When you issue the command you will see something like:

06:57:40 up 3 days, 22:15,  2 users,  load average: 0.93, 0.66, 0.49

(My uptime is lame right now. We had a nasty thunderstorm and I had to shut down my machines).

Some people, like myself, add their uptime to their email signatures. You can see how to do this in my article “Add uptime and/or fortunes to your email signature“.

less is more

One command line issue that might bug you is when you issue a command like dmesg and the output flashes by so quickly you can’t read it. There is a very simple way around this. If you pipe the output of the dmesg command to the less command you can read the output “one page at a time”. To do this you would issue the command like so:

dmesg | less

Or you use more to do the same thing (almost) like:

dmesg | more

The difference? With less you can scroll backwards. With more you can not.

Save that output

But what if you want to save your output of a command like dmesg so you look at it earlier or even email it to someone to look through? You can take multiple screenshots of each less page from dmesg…or…you can direct the output to a file. This is done like so:

dmesg > FILE_NAME

Where FILE_NAME is the name of the file that will hold the output. NOTE: If you will be sending that output to a windows user you might want to include the .txt extension for easy opening.

Final thoughts

Sometimes those “old school” tips can really save your hide. Just because they are “old school” doesn’t mean they don’t have their uses. In fact, I make use of less and output re-direction every day. Once you start using them, you will find yourself using them more and more.

In order for the bash script we will create to work, a single application will have to be installed and the users’ crontab will have to be edited. These are simple tasks and the end result is sure to raise your “geek cred”. No, this will not make your systems run more efficiently, your code compile perfectly, or your breath smell deliciously.  But hopefully you will learn something and impress your friends and family with your trickery.

What to install

It used to be Linux distributions would ship with the Fortune application. That is no longer the case. You will have to install Fortune in order to take advantage of this simple little app. But what does it do? All Fortune does is print a random adage from stored flat-files found in /usr/share/games/fortune. You can add to these files by opening them up and editing them. But first you have to install the application. Since we are going to be dealing with the command line (for bash scripting), let’s install from command. Open up a terminal window and issue the following command:

sudo apt-get install fortune

And fortune will be installed.

Testing

Let’s now test the commands we will be using. From your terminal prompt issue the command:

uptime

and you should see something like:

11:13:45 up 225 day(s), 3 users, load average 0.07, 0.07, 0.02

Now let’s take Fortune out for a test. Issue the command:

fortune

and you should see something like:

Cheer Up! Things are getting worse at a slower rate.

The script

For this script we are going to take advantage of the echo command and we will write to the ~/.sig file, which will then be used for the signature file in your email client. The basic script looks like:

#! /bin/bash

fortune=/usr/games/fortune
rm ~/.sig
touch ~/.sig
echo 'jack wallen' >> ~/.sig
echo `$fortune` >> ~/.sig
echo 'uptime:'  `uptime` >> ~/.sig

NOTE: There are two different “quotes”. The first is the single quote in the fourth line. The second is the back-tick in the fifth and sixth lines. These back-ticks are necessary to indicate a command is in use.

This script does the following:

1. Removes the previous ~/.sig file to start fresh.
2. Creates a new, empty ~/.sig file.
3. Adds my name to the beginning of the ~/.sig file.
4. Appends the output of the fortune command under last line.
5. Appends the string “uptime” (no quotes) followed by the output of the uptime command under the last line.

Create this file (you’ll want to personalize the echo ‘jack wallen’ >> ~/.sig line of course) and save it in a convenient directory. You will then need to give this file executable permission, so issue the following command:

chmod u+x FILENAME

Where FILENAME is the name of the script.

Cron

Now we need to create a cron job that will run the script so that the file isn’t static. Open up your crontab editor with the command:

crontab -e

and add a line like:

* * * * *  /path/to/script

Where /path/to/script is the explicit path to your script you created.

Email

Every email client will be configured differently. But basically all you need to do is go to the signature preferences section and configure your client to use ~/.sig as the file for your email signature. Now every minute that file will be different and your signature will be “dynamic”, containing a random quote and your machine’s uptime.

Of course one might think such a technology would be difficult at best to use. Not so. The developers of Ksplice have created an incredibly easy to use system that allows the administrator to handle critical updates, normally requiring a reboot, as easily as those updates that do not require a reboot.

Getting such a system working does requiring the installation of third party software. This tutorial will walk you through installing Ksplice as well as how to go about updating a currently running kernel with the new system.

Installing Ksplice

Figure 1

To install Ksplice navigate your browser to the Ksplice Uptrack page and click on the link for your particular distribution. If you are using Ubuntu the Gdebi installer will be an option to select from (see Figure 1) . Select Open with and then make sure GDebi is selected. Click OK and the installation will commence.

During the installation a new window will open specific to Ksplice. In this window you will have to agree to a License and then click Forward. Once you have done this the installation will complete.

Using Ksplice

Figure 2

After install is finished Ksplice will automatically open up the update window (see Figure 2) and reveal to you if there are any updates for your currently running kernel. This might very well remind you of the average Linux package management front-end.

In order to install the update(s) click the Install All Updates button to take care of any updates pending.

You will also notice a new icon added to your Notification Area (see Figure 3). This Icon will not only allow you to launch the

Figure 3

Ksplice tool, it will also keep you informed if there are any updates available. Figure 3 shows the Ksplice icon with a pending update.  When your system is up to date the “!” will disappear and leave you with a clean “K” icon.

Command line

What Linux tool is complete without a command line component? Ksplice includes four command line tools for your terminal pleasure:

• uptrack-upgrade: This command will download and install the latest kernel updates available for your system.
• uptrack-install PACKAGE: Will install a specific update (Where PACKAGE is the package name to update.)
• uptrack-remove PACKAGE : Will remove a specific update (Where PACKAGE is the package name to remove).
• uptrack-show PACKAGE: Will show more detail about a specific update (Where PACKAGE is the package name).

Final thoughts

I have been using Linux (and computers) for quite some time. I never thought I would see the day when such a major update to the underlying sub-systems could be pulled off without a reboot. And not only that, it is done as simply as using a GUI interface.  But now we are looking at something special. Ksplice is only now beginning to make serious inroads into reaching that goal of 100% uptime. And now, without having to reboot after a major upgrade, that 100% number is looking closer and closer every day.

The Yahoo Server Monitor Widget is a nice to have widget that is displaying several information about a server on the user’s desktop. It is by far not a complete solution but it works quite nicely for the time the user is working on the PC.

The Server Monitor Widget displays information like CPU Load, Server Uptime, Hard Disk Space, Server Address and Cache which is nice for a quick overview. It pulls the data from the free phpSysInfo script that has to be installed on the server.

This script does not check specific services like MySQL and Email but it gives information if a server is up or down.

Once you have grown your traffic to a fairly decent amount, however, downtimes that affect your site are a complete different story, a nuisance that can mean that hundreds of people are unable to get to your site, most of whom are likely to never come back again. In my experience, even when my hosting company promised 99.8% uptime, this began to increasingly seem like meaningless marketing hype when I started getting emails from friends and strangers alike informing me that my site was down at such and such an hour (many of which downtimes occurred in the early am hours when I wouldn’t have been online anyway).

I also noticed that the net effect of this was that I was becoming a bit paranoid; if my traffic seemed lower than it usually is I immediately wondered if me site had been down. I started looking for a resource that would monitor my site for downtimes and inform me automatically so I didn’t have to spend time wondering about it. This is when I found Montastic.

Montastic is a very simple service: create an account then enter in the URLs of the sites you would like it to monitor (up to a limit of 100 sites). It will then check the sites on your list within 10 minute intervals and from 2 locations. If and when it detects that any of the sites are down, it will immediately report this by email or through RSS. Once the site is back up it will report that as well.

What’s interesting about Montastic is that you are not limited to just your sites. After listing my 3 websites I decided to include 2 blogs that are similar to my main blog just for benchmarking purposes. To my surprise I discovered that while my site went down for about 2 hours once this week, these other sites seemed to be down for a few hours at least every other day, which was interesting to know, and made me think that perhaps my hosting company isn’t so bad after all.

Montastic was created by a team of “open source fanatics” that developed it for their own use and decided to make it available to everyone as a 100% free service.