Upon booting from the CD, type linux text and then press Enter.^[22]

At this point the text installation interface will start. You will be asked whether you want to test the media. These instructions assume you’ve already done so, and therefore can skip that step.

CentOS will then welcome you to the installation. Press Enter to continue.

Choose your language and make a keyboard selection.^[23] If you’re in North America, you will probably just select the defaults.

If you’ve previously formatted your hard drive, you will be asked to initialize the drive, which will erase all data. Select Yes.

The installer will ask if you want to remove the existing partitioning scheme and create a new one. Select Remove all partitions on selected drives and create default layout. If a more appropriate option exists, select that instead. In the drive window, verify that the correct disk drive is selected. (Pressing Tab will cycle through the selections on the screen.) Once the drive window is selected, you can scroll up and down (presuming you have multiple drives) and select which hard drive you wish to install to. Toggle the selections by pressing space bar. Verify that the correct drive is selected, press Tab until the OK button is highlighted, and press Enter.

A message confirming that you want to remove all Linux partitions and create the new partition scheme will be presented. Select Yes.

You will be asked to review the partitioning layout. Feel free to modify the partition scheme if you prefer something different (see the following sidebar for some advice on this); however, the default answer No is fine for light production use where storage requirements will be low.^[24]

A message will appear asking if you’d like to configure the eth0 network interface on your system. Select Yes. Be sure the Activate on boot and Enable IPv4 support options are enabled, then select OK.

If your network provides automatic IP provisioning via DHCP, you can just select OK. Otherwise, select Manual address configuration, enter the appropriate information, and then select OK.

Next, you’ll be asked to provide a hostname. You can either allow the DHCP server to provide one for you (if your network assigns hostnames automatically) or enter one manually, then select OK.

You will be presented with a list of time zones. Highlight your local time zone and select OK.

At this point, you will be asked for a root password. Enter a secure password and type it again to confirm. After entering your secure password, select OK.

Next up will be the package selection. Several packages that you don’t need to install (and that require additional ISO files you probably haven’t downloaded) are selected by default. Deselect all options in the list using the space bar, then select the Customize software selection option. Once you’ve done that, select OK.

You will then be presented with the Package Group Selection screen. Scroll through the whole list, deselecting each item. If any packages are selected, you’ll be prompted for additional CDs that you have not downloaded. We’ll be installing additional packages with the yum application after the operating system is installed. Once you’ve deselected all packages, select OK.

A dependency check will then be performed and a confirmation that installation is ready to begin will be presented. Select OK to start the installation. The filesystem will then be formatted, the installation image transferred to the hard drive, and installation of the system packages performed. Upon installation, you will be asked to reboot. Remove any media in the drives and select the Reboot button.

Once you’ve rebooted your system, you need to run the yum update command to make sure you have the latest base packages. To do this, log in using the username root and the password you created during installation. Once logged in, run the following:

# yum update

Is this ok [y/N]: y

When prompted to install the latest packages, press y and wait for the packages to update. If you’re asked to accept a GPG key, press y. When complete, reboot the system as it is likely the kernel will have been updated^[25]:

# reboot

# yum remove *.i386 -y

Congratulations! You’ve successfully installed and updated the base CentOS system.

Keeping accurate time is essential on your Asterisk system, both for maintaining accurate call detail records and for synchronization with your other programs. You don’t want the times of your voicemail notifications to be off by 10 or 20 minutes, as this can lead to confusion and panic from those who might think their voicemail notifications are taking took too long to be delivered. The ntpd command can be used to ensure that the time on your Asterisk server remains in sync with the rest of the world:

# yum install ntp
...
Is this ok [y/N]: y
...
# ntpdate pool.ntp.org
# chkconfig ntpd on
# service ntpd start

The defaults shipped with CentOS are sufficient to synchronize the time and keep the machine’s time in sync with the rest of the world.

The Ubuntu server install process asks you to add a system user other than root, but CentOS does not. In order to be consistent in the book and to be more secure, we’re going to add another system user and provide it sudo access.^[26] To add the new user, execute the adduser command:

# adduser asteriskpbx
# passwd asteriskpbx
Changing password for user asteriskpbx.
New UNIX password:
Retype new UNIX password:

Now we need to provide the asteriskpbx user sudo access. We do this by modifying the sudoers file with the visudo command. You’ll need to install visudo the first time you use it:

# yum install sudo

With the sudo-related applications and file installed, we can modify the sudoers file. Execute the visudo command and look for the lines shown below:

# visudo

## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)       ALL

With the %wheel line uncommented as shown in our example, save the file by pressing Esc, then typing :wq and pressing Enter. Now open the /etc/group file in your favorite editor (nano is easy to use) and find the line that starts with the word wheel. Modify it like so:

wheel:x:10:root,asteriskpbx

Save the file, log out from root by typing exit, and log in as the asteriskpbx user you created. Test your sudo access by running the following command:

$ sudo ls /root/
[sudo] password for asteriskpbx:

After typing your password, you should get the output of the /root/ directory. If you don’t, go back and verify the steps to make sure you didn’t skip or mistype anything. The rest of the instructions in this chapter will assume that you’re the asteriskpbx user and that you have sudo access.

One last thing needs to done, which will allow you to enter commands without having to enter the full path. By default only root has /sbin/ and /usr/sbin/ in the default system PATH, but we’ll add it to our asteriskpbx user as well since we’ll be running many applications located in those directories.

Start by opening the hidden file .bash_profile located within the asteriskpbx home directory with an editor. We’re then going to append :/usr/sbin:/sbin to the end of the line starting with PATH:

$ vim ~/.bash_profile
PATH=$PATH:$HOME/bin:/usr/sbin:/sbin

As previously, save the file by pressing Esc and then typing :wq and pressing Enter.

With the operating system installed, you’re ready to install the dependencies required for Asterisk. The next section deals with Ubuntu, so you can skip ahead to the section the section called “Software Dependencies”, which provides an in-depth review of the installation process. Alternatively, if you’ve already reviewed the information in that section, you may want to refer back to the the section called “Installation Cheat Sheet” for a high-level review of how to install Asterisk.

Upon booting from the CD, you will be presented with a screen where you can select your language of choice. By default English is the selected language, and after a timeout period, it will be automatically selected. After selecting your language, press Enter.

The next screen will give you several options, the first of which is Install Ubuntu Server. Select it by pressing Enter.

You will then be asked which language to use for the installation (yes, this is slightly redundant). Select your language of choice (the default is English), and press Enter.

You will be presented with a list of countries. Once you’ve found your country and highlighted it, press Enter.

You will then be asked if you would like to use the keyboard layout detector. If you know which keyboard type you have, you can select No and then pick it from a list of formats.

If you are utilizing the keyboard layout detector, you will be prompted to press a series of keys. If you use the keyboard detector and it does not detect your keyboard correctly (typical when installing into a virtual machine via a remote console), you can go back and select from a list manually.

Once you’ve picked your keyboard, the installation will continue by attempting to set up your network automatically. If all goes well, you will be prompted to enter a hostname for your system. You can pick anything you want here, unless your network requires your system to a have a specific hostname. Input it now and then press Enter.

The installer will attempt to contact a Network Time Protocol (NTP) server to synchronize your clock. Ubuntu will then try to autodetect your time zone and present you with its choice. If correct, select Yes, otherwise, select No and you’ll be presented with a list of time zones to select from. Select your time zone, or select from the worldwide list if your time zone is not shown. Once you’ve selected your time zone, press Enter to continue.

The installer will then ask you some questions about partitioning your system. Typically the default is fine, which is to use the guided system, utilizing the entire disk, and to set up the Logical Volume Manager (LVM). Press Enter once you’ve made your selection. Then you’ll be asked which partition to install to, which likely is the only one on your system. Press Enter to continue, at which point you’ll be asked to confirm the changes to the partition table. Select Yes and press Enter to continue.

You will now be asked how much space to use (the default value will be to use the entire disk). Press Enter once you’ve entered and confirmed the amount of space you want to use. The installer will then request one last confirmation before making the changes to the disk. Select Yes to write the changes to disk. The installer will now format the hard disk, write the partitioning scheme to disk, copy the files, and perform the file installation.

When the file installation is complete, you’ll be asked to enter the Full name of the new user, from which a username will be generated. The system will suggest a username, but you are free to change the username to whatever you like.

After entering your username, you’ll be asked to supply a password, and then asked to confirm the password you’ve entered. Ubuntu does a good job of providing a secure system by not providing direct access to root, but rather using the sudo application, which allows you to run commands as root without being the root user. Enter a username,^[28] such as asteriskpbx, and a secure password to continue. You’ll use these to log into the system once the installer ends. The installer will then ask you if you want to encrypt your home directory. This is not necessary and will add CPU overhead.

If your system is behind a web proxy, enter the proxy information now. If you’re not behind a proxy, or don’t know if you are, simply press Enter.

You will then be asked if you want to install updates automatically. The default is to perform no automatic updates, which is what we recommend. Should a system reboot occur, an update to the kernel will render Asterisk nonstartable until you recompile it^[29] (which won’t make you popular). It is better practice to identify updates on a regular basis and perform them manually in a controlled manner. Normally, you would want to advise your users of the expected downtime and schedule the downtime to happen after business hours (or while a redundant system is running). Select No automatic updates and press Enter.

Since we’ll be installing our dependencies with apt-get, we only need to select one package during the install: OpenSSH server. SSH is essential if you wish to perform remote work on the system. However, if your local policy states that your server needs to be managed directly, you may not want to install the OpenSSH server.

After you’ve selected OpenSSH server, press Enter.

If this is the only operating system on the machine (which it likely is), Ubuntu will give you the option to install the GRUB bootloader on your system. It provides this prompt in order to give you the option of skipping the GRUB installation, as it will modify the master boot record (MBR) on your system. If there is another operating system it has failed to detect that has information loaded into the MBR, it’s nice to be able to skip modifying it. If this is the only operating system installed on your server, select Yes.

When the system has finished the install, you’ll be asked to remove any media in the drives and to reboot the system by selecting Continue, at which point the installation will be complete and the system will reboot.

Now that we’ve completed installing Ubuntu Server, we need to perform a system update with apt-get to make sure we have the latest packages installed. You’ll be presented with a login prompt where you’ll log in with the username and password you created in the installer (e.g., asteriskpbx). Once logged in, run the following command:

$ sudo apt-get update
[sudo] password for asteriskpbx:
...
Reading package lists... Done

$ sudo apt-get upgrade
Reading state information... Done
...
Do you want to continue [Y/n]? y

Press Enter when prompted to continue, at which point the latest package updates will be installed. When complete, reboot the system for the changes to take effect as the kernel has probably been updated.

$ sudo reboot

Congratulations! You’ve successfully installed and updated the base Ubuntu Server system.

Keeping accurate time is essential on your Asterisk system, both for maintaining accurate call detail records as well as for synchronization with your other programs. You don’t want the times of your voicemail notifications to be off by 10 or 20 minutes, as this can lead to confusion and panic from those who might think their voicemail notification took too long to be delivered:

$ sudo apt-get install ntp

The default on Ubuntu is to run a time sync server without ever changing the time on your own machine. This won’t work for our needs, so we’ll need to change the configuration file slightly. Because of this, we need to guide you through using a command line editor. The nano editor is already installed on your Ubuntu machine and is remarkably easy to use^[30]:

$ sudo nano /etc/ntp.conf

Your terminal will switch to full-screen output.

Use your arrow keys to move down to the section that looks like

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery

Add two new lines after this section, to allow ntpd to synchronize your time with the outside world, such that the above section now looks like

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify nopeer noquery
restrict -6 default kod notrap nomodify nopeer noquery

restrict -4 127.0.0.1
restrict -6 ::1

That’s everything we need to change, so exit the editor by pressing Ctrl+X. When prompted whether to save the modifications, press Y; nano will additionally ask you for the filename. Just hit Enter to confirm the default /etc/ntp.conf.

Now restart the NTP daemon:

$ sudo /etc/init.d/ntp restart

With the operating system installed, you’re ready to install the dependencies required for Asterisk. The next section provides an in-depth review of the installation process. If you’ve already reviewed the information in the section called “Software Dependencies”, you may want to refer back to the section called “Installation Cheat Sheet” for a high-level review of how to install Asterisk.