Today's small blog post will cover four handy tips, which makes your life on a Linux/bash terminal easier and faster!

One of the most time-saving features of bash is the "search bash history" quick command Ctrl-r. Find a terminal and see what happens when you issue the command. The prompt will say "(reverese-i-search)". Type in the beginning of a command you have used recently, which had some hard-to-remember extra parameters. This can be a scp-command with that awkward flag for pointing out which certificate to use for the connection, or just finding the path to a script deep in the file-system, which you edited the other day but can't remember where it's located. 

Press ctrl-r and type the first one or two letter of the command that you are looking for, and it will find the last executed command for your user which match. Type more letters to qualify the search even further, or press ctrl-r again, to find the next match.

If you are not already familiar with this, you will ask yourself very soon, how you managed to live without it!

You probably know how to put a process in the background by using "&" after a command. You use the command "jobs" to list the processes that you have put in the background, where each command has it's own unique numerical identifier. This ID can be used to kill the process, using "kill %<id>". See image below.

Scripts and programs in the unix-styled-world has a tendency not to send unnecessary (or even necessary ) information back to the command line. However, the exit code of a program can tell a a lot about why the program did not execute as expected. It can also be very useful in scripts and automation, to be able to determine specific exit codes.

To check the exit code of the last executed program, use "echo $?". Example

[[email protected] ~]$ ./my_script.sh --option=invalidValue
[[email protected] ~]$ echo $?
4

It's customary in the unix-world that 0 means "program executed successfully", and everything else means that the program failed in some way.

You know what it's like. You're deep into the file-system, in some obscure configuration directory of an application, and just have to go to your home directory to check a config file. Then you need to find your way back, but was it /opt/app/version/config or /var/app/version/config, or....? 

Just use the command "cd -" to go to the directory you were in last!

[[email protected] tmp]$ cd -
/var/www/demoapp/html/api

"Linux CentOS" may seem like a bit of a redundant headline, but I wanted to stress the L in LAMP. 

Installing Linux is simple these days, you get instructions from a graphical installer with all the information and helpers that you may need. It's not like installing some odd Slackware 3.2 with a buggy 2.0 kernel (which happens to be the first Linux I at least tried to install). So let's start!

To get started, you need to "Insert the CD/DVD" into the virtual server. In this case the CD/DVD is an image file, which you downloaded earlier (see Step 1). 

Open up VirtualBox and right-click on your instance, and select Settings (or click that nice looking Settings icon).  

Select the Storage option in the left menu, the click the Empty label in the "Controller: IDE" section, and click the CD-icon to the right, and finally click the "Chose a virtual CD/DVD disk file...". Find your way to the downloaded CentOS 6.6 image file, and select it.

Time to start the installation! Right-click the instance and select Start, or use the icon next to Settings.  

Important! When you click the screen of a VirtualBox instance, your mouse pointer will be transferred to that environment. If the server does not support mouse operation, you will have no mouse at all. To go out of the VirtualBox-mode, and get the mouse pointer back, press the right Ctrl button!

After you press the Start button, a new window will appear, and a boot loader will show some options, Click on the new window, and use the up/down arrows to select an option. Also practice "releasing" the virtual instance with the right Ctrl button.

The default option will show "Install or Upgrade an existing system", which you should select, so press Enter. Next, odd-looking text will flicker by for a few seconds, and you will be met by a asking if you should test the "install media". Select the Skip option, unless you have reasons to believe that your downloaded ISO-file is broken. 

From here on, you will have a nice graphical interface!

You should now have a screen welcoming you to CentOS 6, and a Next button in the down-rightmost corner. Click it! Continue to chose installation language, and your keyboard layout. 

You will be prompted if you want Basic or Specialized Storage Devices. For a development setup you don't need to think about optimal I/O-performance, so I suggest that you chose Basic Storage Device. After clicking Next, you will get a warning that data could be lost, but since it's a virtualized server, this is not an issue, so click "Yes, discard any data".

The next screen will ask you for the server host name. To keep things simple, you can chose something similar to the name you gave the VirtualBox instance in Step 1. However, in Operations, there are two major schools when it comes to sever host names:

• FQDN: The host name should be formed as a domain path, e.g. frontend-001.eu-1.prod.araneo.local
  
• All-in-the-hostname: Everything goes into a stacked host name, e.g. ara-prodeu01fe001
  

This installation is for a development or test server, so it doesn't really matter, unless you have a specific policy in your company, then ask your Operations team!

In the next step, you will be shown a map with incredibly hard-to-click dots on a world map. Try to find the city closest to you (which is in the same time zone!) and click Next.

Please note: We will configure the server to use UTC at a later stage.

This is the master password, the key which unlocks all the doors, and so on. But don't stress it, trying to find the strongest password you can imagine, as this server will probably won't accept SSH-connections from the internet. 

However, if you know that the server will have a public IP-address and for some reason needs to accept SSH-connections over public internet, and you for some insane reason needs to accept external root logins; then you should select a crazy-strong password here. And then use the time until your first DDOS/brute-force attack, to figure out a better IT-strategy.

At this point, you are going to get the rather scary question what do with any existing data, and how to structure the space. But as this is a virtualized server, using a file disk image, there is no data to lose, so just go for the most aggressive alternative, "Use All Space"!  After pressing Next you will get another confirmation request, but remember that you're not making changes to your host system, just to those hard drive files created earlier, so just click "Write changes to disk".

Now the installation has started. Sit back and relax, or go get some more coffee. In this step, you don't have to do anything. After about four-five sips of coffee, the installation will be done, and you will be prompted to Reboot. 



This takes you to the next chapter of the article: Step 3: Configure the Server.