// Copyright: ©2011 My Company, Inc.
grep -r "My Company, Inc." . | cut -d: -f1 | xargs sed -i 's/My Company, Inc./Matthew Downey/'
bundle gem hello_world
create hello_world/Gemfile
create hello_world/Rakefile
create hello_world/.gitignore
create hello_world/hello_world.gemspec
create hello_world/lib/hello_world.rb
create hello_world/lib/hello_world/version.rb
Initializating git repo in /home/matt/hello_worldmkdir -p hello_world/ext/hello_world
#include "ruby.h" #include <stdio.h> static VALUE method_hello_world(VALUE self) { printf("Hello World!\n"); return Qnil; } VALUE HelloWorldModule; VALUE HelloWorldClass; void Init_hello_world() { HelloWorldModule = rb_define_module("HelloWorld"); HelloWorldClass = rb_define_class_under(HelloWorldModule, "HelloWorld", rb_cObject); rb_define_method(HelloWorldClass, "hello_world", method_hello_world, 0); }
require 'mkmf' create_makefile("hello_world")
require 'hello_world/hello_world' module HelloWorld # Your code goes here... end
require 'rubygems' require 'rake' require 'rake/extensiontask' require 'bundler' Rake::ExtensionTask.new("hello_world") do |extension| extension.lib_dir = "lib/hello_world" end task :chmod do File.chmod(0775, 'lib/hello_world/hello_world.so') end task :build => [:clean, :compile, :chmod] Bundler::GemHelper.install_tasks
# -*- encoding: utf-8 -*- $:.push File.expand_path("../lib", __FILE__) require "hello_world/version" Gem::Specification.new do |s| s.name = "hello_world" s.version = HelloWorld::VERSION s.platform = Gem::Platform::RUBY s.authors = ["Matthew Downey"] s.email = ["mattddowney@gmail.NOSPAM.com"] s.homepage = "http://www.writehack.com" s.summary = %q{Hello World!} s.description = %q{Gem that prints Hello World!} s.rubyforge_project = "hello_world" s.files = `git ls-files`.split("\n") s.test_files = `git ls-files -- {test,spec,features}/*`.split("\n") s.executables = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) } s.require_paths = ["lib"] s.extensions = ["ext/hello_world/extconf.rb"] end
rake build
git init git add . git commit -m 'initial commit'
rake install
ruby-1.9.2-p136 :001 > require 'rubygems' => true ruby-1.9.2-p136 :002 > require 'hello_world' => true ruby-1.9.2-p136 :003 > hello = HelloWorld::HelloWorld.new => #<HelloWorld::HelloWorld:0x000000027d7c40> ruby-1.9.2-p136 :004 > hello.hello_world Hello World! => nil ruby-1.9.2-p136 :005 >
sudo nmap -Pn -sS -p 53 -iR 1000 --open | grep -B 4 "53/tcp open"
I have a virtual machine of Ubuntu 10.10 that I use for development purposes. The other day, I got this message:
Since the box is for development purposes, I have no real need to keep several days worth of logs. So I cooked up a script to delete the logs:
#!/bin/bash # delete archived logfiles for i in `find /var/log -type f \( -name \*.\[0-9\] -o -name \*.bz2 -o -name \*.gz -o -name \*.old \)` do rm $i done # clear remaining logfiles for i in `find /var/log -type f` do cat /dev/null > $i done
I saved it as clearlogs.sh, in my /etc/init.d folder. Then, I made it executable, and created symbolic links in rc0.d and rc6.d to make it run on shutdown and restart:
chmod +x /etc/init.d/clearlogs.sh ln -s /etc/init.d/clearlogs.sh /etc/rc0.d/K10clearlogs.sh ln -s /etc/init.d/clearlogs.sh /etc/rc6.d/K10clearlogs.sh
Now every time I load my system, I have clean logs. I would never do this on a production system or even my primary system, but for a dev box this works great.
PermalinkThis post serves as a marker for my virtual linux lab series. It is a series of tutorials that shows how to install and configure two CentOS 5.5 guests on a Windows 7 host as a virtual lab with VirtualBox. It is geared towards absolute beginners; I designed it to help my fellow linux system administration students at the Community College of Aurora.
Many of us don't have access to a proper lab, but thanks to virtualization technology, we can set one up on a single computer. Hopefully you will learn as much as I did reading these as I did creating them. :)
Check back often, as I will most likely be adding to this series in the future.
PermalinkIf you've been using VirtualBox for a while, you've probably been scratching your head wondering how you can give two virtual machines the ability to communicate. The easiest way to do this is to configure bridged networking. In this tutorial, we are going to configure and test two CentOS 5.5 guests and a Windows 7 host. We also assume you already have guest additions installed.
Make sure your virtual machines are shutdown, then click "Settings." Select "Network" from the list on the left. This will bring up the guest machine's network settings. As you can see, VirtualBox allows a lot of network flexibility, with support for up four adapters and four different networking modes. Click the dropdown box labeled "Attached to" and change it to "Bridged Adapter" like so:
Now we must make sure that we select the proper network adapter that our host is using. On my laptop, I have two adapters, a physical adapter and a wireless one. Since I am connected to my network wirelessly, I need to select my wireless adapter. Click the dropdown box labeled "Name" and select the appropriate adapter that you are connecting with:
After clicking "OK," modify the other virtual machines on the network in the same manner. Start them both.
Bridged networking does a bit of voodoo to retrieve multiple IP addresses from your router with the same adapter card. If you login to your router after your guest OSes are connected, you should notice that there are multiple IP addresses for the same MAC address in your router.
Let's test that everything is working. First, verify that your host can connect to the internet. If that is working properly, and it should be (you are reading this), the next step is to verify internet connectivity on each guest machine. Open up a terminal, and ping google. If everything went okay, you should get something like this:
[matt@localhost ~]$ ping -c 3 google.com PING google.com (209.85.225.106) 56(84) bytes of data. 64 bytes from iy-in-f106.1e100.net (209.85.225.106): icmp_seq=1 ttl=52 time=83.4 ms 64 bytes from iy-in-f106.1e100.net (209.85.225.106): icmp_seq=2 ttl=52 time=82.3 ms 64 bytes from iy-in-f106.1e100.net (209.85.225.106): icmp_seq=3 ttl=52 time=82.9 ms --- google.com ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2000ms rtt min/avg/max/mdev = 82.397/82.942/83.443/0.428 ms
The important thing is at the bottom: all packets that were transmitted were recieved.
Next, let's verify connectivity between the the host and each guest, and in between our two guests. To do this, we need to get the ip addresses for each machine. First, lets get the Windows host's ip address. Open up a command promt by going to "Start" and typing "cmd" into the search box. Now run ipconfig:
C:\Users\Matt>ipconfig
The should produce a fairly decent amount of output. The line we are interested in is near the top, the first IPv4 Address:
IPv4 Address. . . . . . . . . . . : 192.168.1.60
Write this number down.
Now, let's move onto each guest. In linux, the command to get the computer's ip address is ifconfig, and it must be run as root. If you have sudoers configured, and have added /sbin to your path, open up a terminal and type the following:
sudo ifconfig
The line we are looking for is also near the top, listed under our network adapter, which should be eth0. Specifically, we are looking for the second line:
inet addr:192.168.1.114 Bcast:192.168.1.255 Mask:255.255.255.0
The first number in this line is our ip address. Write this down, and do this for each guest. My ip addresses are the following:
| Machine | IP address |
|---|---|
| Windows Host | 192.168.1.60 |
| CentOS Guest #1 | 192.168.1.114 |
| CentOS Guest #2 | 192.168.1.111 |
To verify that I can connect to each guest from my host, I just ping them from my Windows command prompt. The Windows and linux ping commands are different, yet similar. For Windows, there's no need to specify a number of packets to send. Let's ping both guests now:
As you can see, I can reach both guests from my Windows host just fine.
Next, we'll ping the host and other guest from each guest:
Again, no errors-- everything appears to be working fine. Now we can move onto more interesting things, like using ssh and configuring various servers.
PermalinkOne nice thing about using virtual machines is that you can make copies of them. This way if you install and configure a machine to your liking, you can just clone it and get another machine without having to go through the hassle of installation and configuration again. You can't just copy the .vdi file, however, because each virtual disk has a unique id. You can however, clone a disk relatively easily with the VBoxManage command.
In this tutorial we will be using a Windows 7 host, and cloning the hard disk for the CentOS 5.5 install that we performed in an earlier post. We will also assume that VBoxManage is in the Windows path. Open up a command prompt on the Windows host by clicking "Start" and typing "cmd" into the search box.
Once we open up a command prompt, we need to navigate to the directory where our hard disks are stored. These are in the your user's directory in the ".Virtualbox\HardDisks" subfolder. When you first open the command prompt, you should already be in your user's directory. Change to the hard disks folder by typing the following:
cd .VirtualBox\HardDisksAt this point, you can type "dir" to get a list of your .vdi files. If you followed along in the previous tutorial, you probably installed CentOS on a disk named "CentOS.vdi".
The syntax for the command to clone the disk is simple, "VBoxManage clonehd [infile.vdi] [outfile.vdi]". To clone disk named "CentOS.vdi" and create a duplicate "CentOS2.vdi" we type:
VBoxManage clonehd CentOS.vdi CentOS2.vdi
This process will take a few minutes.
To make the disk available to VirtualBox, we need to add it in the "Virtual Media Manager." From the main VirtualBox window, go to "File > Virtual Media Manager." Click "Add" and select the new disk we just cloned. Click "OK" and it should now be available in the dropdown box when you create a new machine.
PermalinkVirtualBox comes with a useful command line utility called VBoxManage that allows you to do anything that can be done with the GUI tool and more. The only problem is it isn't added to the Windows path. Adding it to the path is relatively easy.
First, bring up the System properties. The easiest way to access this is through a keyboard shortcut, "Windows-Break." Alternatively, you can get there by clicking "Start," right-clicking on "Computer," and then selecting "Properties."
Now click "Advanced system settings" in the list on the left hand side.
Click the "Environment Variables..." button towards the bottom of this dialog.
This will open up an "Environment Variables" dialog. In the section labeled "System variables" scroll down to the one that says "Path" and click "Edit..."
Append the following to the end of the box labeled "Variable value" and click "OK." If you installed VirtualBox to another directory, use that instead:
;C:\Program Files\Oracle\VirtualBox
Click "OK" on the "Environment Variables" and "System Properties" dialogs. Open a Windows command prompt by clicking "Start" and then typing "cmd" into the search box. If everything went well, you should be able to type the following to get a list of your virtual machines:
VBoxManage list vms
Virtualbox allows you to share files between the guest and host operating systems. For the purposes of this tutorial, the host OS is Windows 7 and the guest OS is CentOS 5.5, although we could use any flavor of Linux. This tutorial also assumes that you have guest additions installed.
To start with, create a folder on the host operating system. You can exist anywhere you like. For ease of access, we'll just place ours on the desktop. To do this, right-click on the Windows desktop and select "New > Folder." Give this folder the name "share."
Next, run Virtualbox and start the guest operating system. From Virtualbox's menu, select "Devices > Shared Folders."
This will open up a dialog box with the title "Shared Folders."
On the top right of the dialog, click on the folder icon with the green plus sign. This will open up a file browser.
Browse to the share folder that was created on the host desktop and make sure to check the box labeled "Make Permanent." If this box is unchecked, it will create a transient share folder that will disappear the next time the guest OS is started. Click OK. The share should now appear in the list under the heading labeled "Machine Folders."
After clicking OK, the configuration is complete on the host operating system. Now we need to configure the guest OS. Login to the guest machine, and open up a terminal. We need to create a directory for the shared folder to reside. This can be anywhere on the filesystem, but for our purposes, we will be creating the directory /share. Since we will be creating this directory in the root folder, we need be root. Either change to the root user using su -, or prefix the command with sudo. We will be using sudo. Issue the following command:
sudo mkdir /share
Now we must mount the host's share folder to the /share directory we just created on the guest operating system. We could do this with the mount command, however that would require us to mount the folder every time we start the guest OS. Since we want this share to be permanent, it needs to be mounted on startup. To do this, we must add a line to the /etc/fstab file. We must be root to edit this file, so issue the following command:
sudo vi /etc/fstab
This will open up the /etc/fstab in vi. Scroll down to the bottom of the file, and push o to switch to edit mode and insert the following line at the end of the file:
share /share vboxsf defaults 0 0
The first column is the name of the share we are mounting, given to us from the name column of the shared folders dialog. The second column is the mountpoint, the name of the directory we created on the guest that we will be mounting the folder to. The third column is the filesystem type, and the remaining columns are various options, of which we will use the default setting. After adding the line, save and edit the editor using :wq.
At this point, everything is setup, and all that is required is a reboot of the guest OS for the system to reload the /etc/fstab file. But before we do so, it would be nice to have a shortcut to our share on our linux desktop. To do this, we need to create a symbolic link, and store it in the ~/Desktop directory. Make sure you are logged in as your normal user, and type the following into the terminal:
ln -s /share ~/Desktop/share
A link to the /share folder should now appear on your desktop.
Now, reboot the guest OS and test the shared folder by placing some files into it. If everything went well, the files should show up in the folder on both the host and guest operating systems.
PermalinkVirtualbox is nice because it comes with a set of drivers called guest additions, that allow you to be able to resize the guest window and provide seamless integration for the mouse and keyboard, without the need for using the host key. Installing guest additions also allows for more advanced networking modes, among other things. This tutorial assumes that your guest OS is CentOS or other Red Hat based, although the installation is similar for all distributions, you just have to substitute your distros package manager for yum.
To get started we need to install a few packages as root. Type the following into a terminal:
sudo yum install gcc kernel kernel-devel
Yum should ask you if you really want to install the packages, so tell it yes. After the packages have installed, reboot the virtual machine, and login to the desktop. Then, from the Virtualbox menu, select "Devices > Install Guest Additions."
This should automount the guest additions, which will show up as a CD on the desktop. Open another terminal, and switch to the root user:
su -
Enter your password and change to the directory where the guest additions reside:
cd /media/VBOXADDITIONS_3.2.8_64453
You might have a different version of guest additions, so substitute accordingly.
Next, depending on your guest machine's architecture, run either VBoxLinuxAdditions-x86.run or VBoxLinuxAdditions-amd64.run using sh.
sh VBoxLinuxAdditions-amd64.run
This will take a couple of minutes, just be patient. The system is recompiling the kernel with the new guest addition drivers. After it finishes, reboot. After your machine finishes booting, if everything went well you should be able to resize the window and the mouse will move seamlessly from guest to host without the need for using the host key.
Permalink