Open Source vs. Closed Source (12.1.1.1)

Like desktops and laptops, mobile devices use an OS to run software, as shown in Figure 12-1. This chapter focuses on the two most commonly used mobile operating systems: Android, developed by Google, and iOS, developed by Apple.

In order for users to be able to analyze and modify software, they must be able to see the source code. Source code is a sequence of instructions written in human-readable language, before it is turned into machine language (zeros and ones). The source code is an important component of free software as it allows users to analyze and eventually modify the code. When a developer chooses to provide the source code, the software is said to be open source. If the program’s source code is not published, the software is said to be closed source.

Android is an open source, Linux-based smartphone/tablet operating system developed by the Open Handset Alliance, primarily driven by Google. Released in 2008 on the HTC Dream, Android OS has been customized for use on a wide range of electronic devices. Because Android is open source and customizable, programmers can use it to operate devices such as laptops, smart TVs, and e-book readers. There have even been Android installations in devices such as cameras, navigation systems, and portable media players. Figure 12-2 shows Android running on a tablet.

iOS is a closed source Unix-based operating system for Apple’s iPhone smartphone and iPad tablet. Released in 2007 on the first iPhone, the Apple iOS source code was not released to the public. Copying, modifying, or redistributing iOS requires permission from Apple. Figure 12-3 shows iOS running on an iPhone.

iOS is not the only closed source OS for mobile devices. Microsoft has also created versions of Windows for its mobile devices, including Windows CE, Windows Phone 7, and Windows Phone 8. With the development of Windows 10 Mobile, shown in Figure 12-4, Microsoft provides a very similar user interface and use of code on all Microsoft devices, including Windows 10 Mobile phones and Surface tablets.

Applications and Content Sources (12.1.1.2)

Apps are programs that are executed on mobile devices. An app is written and compiled for a specific mobile operating system, such as Apple iOS, Android, or Windows. Mobile devices come with a number of different apps preinstalled to provide basic functionality, as shown in Figure 12-5. There are apps to make phone calls, send and receive email, listen to music, take pictures, and play videos or video games.

Apps are used on mobile devices the same way that programs are used on computers. Instead of being installed from an optical disc, apps are downloaded from a content source. Some apps can be downloaded for free, and others must be purchased.

Apps for Apple iOS mobile devices are available for free or purchase from the App Store, shown in Figure 12-6. Apple uses a walled garden model for its apps, which means the apps must be submitted to and approved by Apple before they are released to users. This helps prevent the spread of malware and malicious code. Third-party developers can create apps for iOS devices by using Apple’s Software Development Kit (SDK) Xcode and the Swift programming language. Note that Xcode can only be installed on computers running OS X.

Android apps are available from both Google Play, shown in Figure 12-7, and third-party sites, such as Amazon’s App Store. Android Studio, a Java-based SDK, is available on Linux, Windows, and OS X. Android apps run in a sandbox and have only the privileges enabled by the user. A prompt appears if an app needs to obtain permissions. Permissions are granted via the app’s Settings page.

Third-party or custom programs are installed directly by using an Android Application Package (apk) file. This gives users the ability to directly install apps without going through the storefront interface, in a process known as sideloading.

Home Screen Items (12.1.2.1)

Much like a desktop or laptop computer, a mobile device organizes icons and widgets on multiple screens for easy access, as shown in Figure 12-8.

One screen is designated as the home screen. Additional screens are accessed by sliding the home screen to the left or right. Each screen contains navigation icons, the main area where icons and widgets are accessed, and notification and system icons, as shown in Figure 12-9. The screen indicator displays which screen is currently active.

The Android OS has a system bar for navigating apps and screens, as shown in Figure 12-10. The system bar is always displayed at the bottom of every screen.

The system bar contains the following buttons:

• Back: Returns to the previous screen. If the onscreen keyboard is displayed, this button closes it. By continuing to tap the Back button, you can navigate through the previous screens until the home screen is displayed.

• Home: Returns to the home screen.

• Recent Apps: Opens thumbnail images of recently used apps. To open an app, touch its thumbnail. Swipe a thumbnail to remove it from the list.

• Menu: If available, Menu shows additional options for the current screen.

Each Android device has an area that contains system icons, such as the clock, battery status, and radio signal status for Wi-Fi and provider networks. Figure 12-11 shows display status icons indicating communication activity for apps such as email, text messaging, and Facebook.

To open the notification area on Android devices, swipe down from the top of the screen. You can do the following when notifications are open:

• Respond to a notification by touching it.

• Dismiss a notification by swiping it off the screen to either side.

• Dismiss all notifications with the icon.

• Toggle often-used settings.

• Adjust the brightness of the screen.

• Open the Settings menu with the quick settings icon.

Home Screen Items (12.1.3.1)

The iOS interface works in much the same way as the Android interface. Screens are used to organize apps (see Figure 12-12), and apps are launched with a touch. There are some very important differences:

• No navigation icons: A physical button may have to be pressed instead of touching navigation icons.

• No widgets: Only apps and other content can be installed on iOS device screens.

• No app shortcuts: Each app on a home screen is the actual app, not a shortcut.

Unlike Android devices, iOS devices do not use navigation icons to perform functions. On iPhone versions prior to the iPhone X, a single physical button called the Home button, shown in Figure 12-13, performs many of the same functions as the Android navigation buttons.

The Home button is at the bottom of the device and can perform many functions. The following are some common functions in iOS:

• Wake the device: In versions prior to iPhone X, when the device’s screen is off, press the Home button once to turn it on. On iPhone X, you can wake the device using either facial recognition or by raising the phone and tapping the screen. (Raise to wake is also available on iPhone versions 6s and later.)

• Return to the home screen: In versions prior to iPhone X, press the Home button while using an app to return to the last home screen that was used. On iPhone X, return to the home screen by swiping the screen up from the bottom.

• Start Siri or voice control: In versions prior to iPhone X, press and hold the Home button to start Siri or voice control. Siri is special software that understands advanced voice controls. On iPhone X, launch Siri by pressing and holding the side button.

iOS devices have a notification area called Notification Center that displays all alerts in one location, as shown in Figure 12-14. To open the notification area on iOS devices, touch the top center of the screen and swipe down. Once in Notification Center, you can browse notifications and alerts, dismiss them, clear them, and adjust them as necessary.

iOS devices allow the user to quickly access common settings and switches, shown in Figure 12-15, even if the device is locked. To access the commonly used settings menu, swipe up from the very bottom of any screen. From the commonly used settings screen, a user can:

• Toggle commonly used settings such as Airplane mode, Wi-Fi, Bluetooth, Do Not Disturb mode, and screen rotation lock

• Adjust screen brightness

• Control the music player

• Access AirDrop

• Access the Flashlight, Clock, Calendar, and Camera apps

From any screen of an iOS device, touch the screen—any part of the screen except the very top or the very bottom—and drag down to reveal the Spotlight search field, shown in Figure 12-16. When the Spotlight search field is revealed, type what you’re looking for. iOS Spotlight shows suggestions from many sources, including apps on the device, the Internet, iTunes, the App Store, and nearby locations. Spotlight also automatically updates the results as you type.

Screen Orientation (12.1.4.1)

Most mobile devices can be used in either portrait or landscape mode, as shown in Figure 12-17. A sensor inside the device, called an accelerometer, detects how the device is being held and changes the screen orientation appropriately. Users can choose the viewing mode that is the most comfortable for them for different types of content or applications. Content is automatically rotated to the position of the device. This feature is useful, for example, when taking a photograph. When the device is turned to landscape mode, the Camera app also turns to landscape mode. Also, when a user is writing a text, turning the device to landscape mode automatically turns the app to landscape mode, making the keyboard larger and wider.

A device may also have a gyroscope to provide more accurate movement readings. A gyroscope allows a device to be used as a control mechanism for driving games where the phone or tablet itself functions as a steering wheel.

Android Screen Auto-Rotation Setting

When using an Android device, to enable auto rotation, open the notifications panel and turn on the auto-rotate function by tapping the screen rotation icon, indicated in Figure 12-18.

iOS Screen Auto-Rotation Setting

When using an iOS device, to enable automatic rotation, swipe up from the bottom or down from the top (depending on your device) to open the Control Center. Then tap the screen rotation lock icon, shown in Figure 12-19, until it is turned off.

Screen Calibration (12.1.4.2)

When using a mobile device, you may need to adjust the brightness of the screen (see Figure 12-20). When bright sunlight makes the screen difficult to read, increase the brightness level. Inversely, very low brightness is helpful when reading a book on a mobile device at night. Some mobile devices can be configured to automatically adjust the brightness depending on the amount of surrounding light. The device must have a light sensor to use auto-brightness.

The LCD screen component for most mobile devices consumes the most battery power on the device. Lowering the brightness or using auto-brightness helps conserve battery power. Set the brightness to the lowest setting to get the most battery life from the device.

Android Brightness Menu

When using an Android device, to configure screen brightness, swipe down from the very top of the screen and use the path Display > Brightness, then slide the brightness to the desired level, as shown in Figure 12-21.

Alternatively, tap the Adaptive Brightness toggle to allow the device to determine the optimal screen brightness based on the amount of ambient light.

iOS Display & Brightness Menu

When using an iOS device, to configure screen brightness, swipe up from the very bottom of the screen and slide the brightness bar up or down to vary the brightness. Alternatively, to configure brightness in the Settings menu, tap Settings > Display & Brightness then slide the brightness to the desired level, as shown in Figure 12-22.

GPS (12.1.4.3)

Another common feature of mobile devices is the ability to work with the Global Positioning System (GPS). GPS is a navigation system, shown in Figure 12-23, that determines the time and geographical location of the device by using messages from satellites in space and a receiver on Earth. A GPS radio receiver uses at least four satellites to calculate position, based on the messages. GPS is very accurate and can be used under most weather conditions. However, dense foliage, tunnels, and tall buildings can interrupt satellite signals. GPS receivers must have line-of-sight to GPS satellites and do not work indoors. Indoor Positioning Systems (IPS) can determine location by triangulating the position of the device based on proximity to other radio signals, such as Wi-Fi access points.

GPS services allow app vendors and websites to know the location of a device and offer location-specific services (such as local weather and advertising). This is called geotracking.

Android Location Services

To enable GPS on Android devices, tap Settings > Location, then tap on the toggle to turn on location services, as shown in Figure 12-24.

iOS Location Services

To enable GPS on iOS devices, tap Settings > Privacy, then toggle Location Services on, as shown in Figure 12-25.

12.1.4.4 Lab - Mobile Device Features

In this lab, you will learn about mobile device features.

Wi-Fi Calling (12.1.4.5)

Instead of using the cellular carrier’s network, a modern smartphone can use the Internet to transport voice calls by taking advantage of a local Wi-Fi hotspot (see Figure 12-26). This is called Wi-Fi calling. Locations such as coffeeshops, workplaces, libraries, and homes usually have Wi-Fi networks connected to the Internet. A phone can transport voice calls through a local Wi-Fi hotspot. If there is no Wi-Fi hotspot within reach, the phone uses the cellular carrier’s network to transport voice calls.

Wi-Fi calling is very useful in areas with poor cellular coverage because it uses a local Wi-Fi hotspot to fill the gaps. The Wi-Fi hotspot must be able to guarantee a throughput of at least 1 Mbps to the Internet for a good-quality call. When Wi-Fi calling is enabled and in use during a voice call, the phone displays “Wi-Fi” next to the carrier name.

Enabling Wi-Fi Calling on Android

To enable Wi-Fi calling on Android, tap Settings > More (under the Wireless & Networks section), tap on Wi-Fi Calling as shown in Figure 12-27 to expose the on/off toggle. Tap on the toggle to turn it on.

Enabling Wi-Fi Calling on iOS

To enable Wi-Fi calling on iOS, tap Settings > Phone > Wi-Fi Calling, then toggle on Allow Wi-Fi Calls, as shown in Figure 12-28.

Note

Not all cellular carriers allow Wi-Fi calling. If you cannot enable it on your phone, your carrier or mobile device probably does not support it.

NFC Payment (12.1.4.6)

Mobile payment refers to any payments made through a mobile phone. You can make mobile payments in several ways:

• Premium SMS-based transactional payments: Consumers send an SMS message to a carrier’s special phone number containing a payment request. The seller is informed that the payment has been received and is cleared to release the goods. The charge is then added to the customer’s phone bill. Slow speed, poor reliability, and poor security are a few shortcomings of this method.

• Direct mobile billing: By using a mobile billing option during checkout, a user identifies himself or herself (usually through two-factor authentication) and allows the charge to be added to the mobile service bill. This type of billing is very popular in Asia and has several benefits: security, convenience, and no need for bank cards or credit cards.

• Mobile web payments: With this method, a consumer uses the Web or dedicated apps to complete a payment transaction. This method relies on Wireless Application Protocol (WAP) and usually requires the use of a credit card or a pre-registered online payment solution, such as PayPal.

• Contactless NFC (Near Field Communication): This method is used mostly in physical store transactions. A consumer pays for goods or services by waving the phone near the payment system. Based on a unique ID, the payment is charged directly against a prepaid account, bank account, or credit card. NFC payments are also used in mass-transportation services, for public parking, and in many other consumer areas.

Virtual Private Network (12.1.4.7)

A virtual private network (VPN) is a private network that uses a public network (usually the Internet) to connect remote sites or users together (see Figure 12-29). Instead of using a dedicated leased line, a VPN uses “virtual” connections routed through the Internet from the company’s private network to the remote site or employee.

Many companies create their own VPNs to accommodate the needs of remote employees and distant offices. With the proliferation of mobile devices, it was a natural move to add VPN clients to smartphones and tablets.

When a VPN is established from a client to a server, the client accesses the network behind the server as if it were connected directly to that network. Because VPN protocols also allow for data encryption, the communication between client and server is secure.

When the VPN information has been added to the device, the VPN connection must be started before traffic can be sent and received through it.

Configuring a VPN Connection on Android

To create a new VPN connection on Android, tap Settings > More (under the Wireless & Networks section) > VPN, tap on the + sign to add a VPN connection, and enter the VPN information (see Figure 12-30).

Starting a VPN Connection on Android

To start a VPN connection on Android, tap Settings > General > VPN, select the desired VPN connection, enter the username and password, then tap CONNECT (see Figure 12-31).

Configuring a VPN Connection on iOS

To create a new VPN connection on iOS, tap Settings > General > VPN > Add VPN Configuration, then fill in the screen shown in Figure 12-32.

Starting a VPN Connection on iOS

To start a VPN connection on iOS, tap Settings and toggle VPN on, as shown in Figure 12-33.

Virtual Assistants (12.1.4.8)

A digital assistant, sometimes called a virtual assistant, is a program that can understand natural conversational language and perform tasks for the end user. Modern mobile devices are powerful computers, which makes them a perfect platform for digital assistants. Popular digital assistants include Google Now for Android, Siri for iOS, and Cortana for Windows Phone 8.1 and Windows 10 Mobile.

Digital assistants rely on artificial intelligence, machine learning, and voice recognition technology, as shown in Figure 12-34, to understand conversational-style voice commands. As the end user interacts with a digital assistant, sophisticated algorithms predict the user’s needs and fulfill requests. By pairing simple voice requests with other inputs, such as GPS location, digital assistants can perform tasks such as playing a specific song, performing a web search, taking a note, or sending an email.

Google Now

To access Google Now on an Android device, simply say “Okay google,” and Google Now begins listening to requests, as shown in Figure 12-35.

Siri

To access Siri on an iOS device, press and hold the Home button. Siri begins listening to requests, as shown in Figure 12-36. Alternatively, you can configure Siri to start listening to commands when it hears “Hey Siri.” To enable “Hey Siri,” tap Settings > Siri & Search and toggle Listen for “Hey Siri” on.

What Do You Already Know? - Locks (12.2.1.1)

It is imperative that a mobile device be protected by a screen lock. There are five types of screen locks: face, passcode, pattern, swipe, and fingerprint.

Read the scenario and select the lock that is used in each case.

Restrictions on Failed Login Attempts (12.2.1.3)

When a passcode has been properly implemented, unlocking a mobile device requires entering the correct PIN, password, pattern, or another passcode type. In theory, a passcode, such as a PIN, could be guessed given enough time and perseverance. To prevent someone from trying to guess a passcode, mobile devices can be set to perform defined actions after a certain number of incorrect attempts have been made.

For Android devices, shown in Figure 12-37, the number of failed attempts before lockout depends on the device and version of Android OS. It is common for an Android device to lock when a passcode has failed from 4 to 12 times. After a device is locked, you can unlock it by entering the Gmail account information used to set up the device.

iOS Erase Data

For iOS devices, you can turn on the Erase Data option, as shown in Figure 12-38. If the passcode fails 10 times, the screen goes black, and all data on the device is deleted. To restore the iOS device and data, if you have backups, use either the Restore and Backup option in iTunes or the Manage Storage option in iCloud.

iOS GUI

On iOS, to increase security, the passcode is used as part of the encryption key for the entire system. Because the passcode is not stored anywhere, no one (including Apple) can gain access to the user data on iOS devices without the passcode. The system depends on the user providing the passcode before the system can be unlocked and decrypted for use. A forgotten passcode renders user data unreachable, as shown in Figure 12-39, and the user must perform a full restore from a backup saved in iTunes or iCloud.

12.2.1.4 Check your Understanding - Screen Locks and Biometric Authentication

Refer to the online course to complete this activity.

Remote Backup (12.2.2.1)

Mobile device data can be lost due to device failure or the loss or theft of the device. Data must be backed up periodically to ensure that it can be recovered, if needed. With mobile devices, storage is often limited and not removable. To overcome these limitations, remote backups can be performed. With a remote backup, a device copies its data to cloud storage using a backup app. If data needs to be restored, run the backup app and access the website to retrieve the data.

Most mobile operating systems come with a user account linked to the vendor’s cloud service, such as iCloud for iOS, shown in Figure 12-40, Google Sync for Android, or OneDrive for Microsoft. The user can enable automatic backups to the cloud for data, apps, and settings. In addition, third-party backup providers, such as Dropbox, can be used. A mobile device can also be backed up to a PC. iOS supports backups on iTunes running on a PC. Another option is to configure mobile device management (MDM) software to automatically back up user devices.

Locator Applications (12.2.2.2)

If a mobile device is misplaced or stolen, it is possible to find it by using a locator application. A locator app should be installed and configured on each mobile device before it is lost. Both Android and iOS have apps for remotely locating a device.

Apple’s Find My iPhone and Android’s Device Manager allow a user to locate, ring, or lock a lost device or to erase data from the device. To manage a lost Android device, the user must visit the Android Device Manager Dashboard, hosted at https://www.google.com/android/devicemanager, and log in with the Google account used on the Android device. Android Device Manager is included and enabled by default on Android 5.x and can be found under Settings > Security > Device Administration.

iOS users can use the Find My iPhone app on different iOS devices to help locate lost devices (see Figure 12-41). After installing the app, the user can start it and follow the instructions to configure the software.

After the device is located, you might be able to perform additional functions, such as sending a message or playing a sound. These options are useful if you have misplaced your device. If the device is close by, playing a sound can help you find it. If the device is at another location, sending a message to display on the screen allows someone to contact you after finding the device.

Remote Lock and Remote Wipe (12.2.2.3)

If attempts to locate a mobile device have failed, other security features can be used to prevent data on the device from being compromised (see Figure 12-42). Usually, the same apps that perform remote location services have security features. Two of the most common remote security features are remote lock and remote wipe.

Remote Lock

The remote lock feature for iOS devices is called Lost Mode (see Figure 12-43). The Android Device Manager calls this feature Lock. Both of these features allow you to lock the device with a passcode, so others cannot gain access to the data in the device. For example, the user can display custom messages or prevent the phone from ringing to indicate incoming calls or text messages.

Remote Wipe

The remote wipe feature for iOS devices is called Erase iPhone (see Figure 12-44). The Android Device Manager calls this feature Erase. Both Erase iPhone and Erase delete all data from the device and return it to a factory state. To restore data to the device, an Android user must set up the device using a Gmail account, and an iOS user must synchronize the device to iTunes.

Most mobile device operating systems provide a full device encryption feature. Full device encryption can prevent anyone in possession of the device from circumventing the device’s access controls and reading the raw data stored in memory.

All user data on an iOS device is always encrypted, and the key is stored on the device. When Erase iPhone or Erase is used to “wipe” the device, the OS deletes the key, and the data becomes inaccessible. Data protection encryption is enabled automatically when a password lock is configured on the device.

On Android OS, encryption is enabled through Settings > Security. Android uses full-disk encryption with a passcode-derived key.

12.2.2.4 Check Your Understanding - Cloud-Enabled Services for Mobile Devices

Refer to the online course to complete this activity.

Antivirus (12.2.3.1)

All computers are vulnerable to malicious software. Smartphones and other mobile devices are computers and are also vulnerable. Antivirus apps (see Figure 12-45) are available for both Android and iOS. Depending on the permissions granted to an antivirus app when it is installed on an Android device, the app might not be able to scan files automatically or run scheduled scans. File scans must be initiated manually. iOS does not allow automatic or scheduled scans. This safety feature prevents malicious programs from using unauthorized resources or contaminating other apps or the OS. Some antivirus apps also provide services such as locator services, remote lock, and remote wipe.

Mobile device apps run in a sandbox, which is a location of the OS that keeps code isolated from other resources and other code. It is difficult for malicious programs to infect a mobile device because apps are run inside the sandbox. An Android app asks for permission to access certain resources upon installation. A malicious app has access to any resources that were allowed permission during installation. This is another reason it is important to download apps only from trusted sources. A trusted app source is a source that is authenticated and authorized by a service provider. The service provider issues the developer a certificate to use to sign apps and identify them as trusted.

Due to the nature of a sandbox, malicious software does not usually damage mobile devices; it is far more likely for a mobile device to transfer a malicious program to another device, such as a laptop or desktop. For example, if a malicious program is downloaded from email, the Internet, or another device, the malicious program could be placed on a laptop the next time it is connected to the mobile device.

To prevent the malicious program from infecting additional devices, a firewall can be used. Firewall apps for mobile devices can monitor app activity and prevent connections to specific ports or IP addresses. Because a mobile device firewall must be able to control other apps, it works at a higher (root) permission level. A NoRoot Firewall works by creating a VPN and then controlling app access to the VPN.

Rooting and Jailbreaking (12.2.3.2)

Mobile operating systems are usually protected by a number of software restrictions. An unmodified copy of iOS, for example, executes only authorized code and allows very limited user access to its file system.

Rooting and jailbreaking are two methods for removing restrictions and protections added to mobile operating systems. They make it possible to circumvent the usual operation of the device operating system to gain superuser or root administrator permissions. Rooting is used on Android devices to gain privileged or root-level access for modifying code or installing software that is not intended for the device. Jailbreaking is typically used on iOS devices to remove manufacturer restrictions and make it possible to run arbitrary user code and grant users full access to the file system and full access to kernel modules (see Figure 12-46).

Rooting or jailbreaking a mobile device usually voids the manufacturer’s warranty. It is not recommended that you modify a customer’s mobile device in this way. Nevertheless, a large group of users choose to remove the restrictions on their own devices. Rooting or jailbreaking a mobile device makes it possible to heavily customize the GUI, make modifications to the OS to improve the speed and responsiveness of the device, and install apps from secondary or unsupported sources.

Jailbreaking exploits vulnerabilities in iOS. When a usable vulnerability is found, a program is written. This program is the actual jailbreak software, and it is then distributed on the Internet. Apple discourages jailbreaking and actively works to eliminate vulnerabilities that make jailbreaking possible on iOS. In addition to the OS updates and bug fixes, new iOS releases usually include patches to eliminate known vulnerabilities that allow jailbreaking. When iOS vulnerabilities are fixed by updates, hackers are forced to start over.

Patching and Updating Operating Systems (12.2.3.3)

As you can update the OS on a desktop or laptop, you can update or patch the OS on a mobile device. Updates add functionality or increase performance. Patches can fix security problems or issues with hardware and software.

Because there are many different Android mobile devices, updates and patches are not released as one package for all devices. Sometimes a new version of Android cannot be installed on older devices whose hardware does not meet the minimum specifications. These devices might receive patches to fix known issues but may not receive OS upgrades.

Android updates and patches are delivered using an automated process. When a carrier or manufacturer has an update for a device, a notification on the device indicates that an update is ready, as shown in Figure 12-47. Touch the update to begin the download and installation process.

iOS updates also use an automated process for delivery, and devices that do not meet the hardware requirements are excluded. To check for updates to iOS, connect the device to iTunes. A notice to download opens if updates are available. To manually check for updates, click the Check for Update button in the iTunes Summary pane.

Two other types of updates for mobile device radio firmware are important. These baseband updates consist of the Preferred Roaming List (PRL) and the Primary Rate ISDN (PRI). The PRL is configuration information that a cellular phone needs to communicate on networks other than its own so that a call can be made outside the carrier’s network. The PRI configures the data rates between the device and the cell tower. This ensures that the device is able to communicate with the tower at the correct rate.

Introduction to Linux and macOS Operating Systems (12.3.1.1)

Two file systems (see Figure 12-48) used on most Linux operating systems are ext3, which is a 64-bit file system with support for journaling, and ext4, which delivers significantly better performance than ext3. Linux can also support FAT and FAT32. In addition, Network File System (NFS) can be used to mount remote storage devices into the local file system.

Most installations of Linux also support the creation of a swap partition to use as swap space. The OS uses the swap partition to supplement system RAM. If applications or data files use up all the available space in RAM, data is written to the swap space on a disk and is treated as if it were stored in RAM.

Apple Mac workstations have their own file system, Extended Hierarchical File System (HFS Plus). This file system supports many of the same features as NTFS in Windows but not native file/folder encryption. In macOS High Sierra and later, HFS Plus was updated to Apple File System (APFS), which supports native file encryption. HFS Plus has a maximum volume and file size of 8 EB.

Unix

Unix, shown in Figure 12-49, is a proprietary operating system written in the C programming language. macOS and iOS are based on the Berkeley Standard Distribution (BSD) version of Unix.

GNU/Linux is an open source, independently developed operating system that is compatible with Unix commands. Android and many OS distributions rely on the Linux kernel.

Linux

Linux operating systems are used in embedded systems, wearable devices, smartwatches, cell phones, netbooks, PCs, servers, and supercomputers. There are many different distributions (or distros) of Linux, including SUSE, Red Hat, CentOS, Fedora, Debian, Ubuntu (see Figure 12-50), and Mint. Each distro adds specific packages and interfaces to the generic Linux kernel and provides different support options. Most distributions provide a GUI interface.

In most cases, a distro is a complete Linux implementation that includes the kernel, shell, applications, and utilities. Each Linux distribution vendor packages software, distributes installation media, and provides support.

macOS

The operating system for Apple computers, macOS (see Figure 12-51), is developed from the Unix kernel, although macOS is a closed source operating system.

Since its release in 2001, macOS has undergone regular updates and revisions to keep pace with Apple Mac hardware updates. Updates and new OS versions are distributed for free through the App Store. Some older Mac computers may not be able to run the newest macOS versions. You can check support.apple.com/specs for the technical specifications of any macOS release.

macOS supports remote network installation called NetBoot, which is similar to Preboot Execution Environment (PXE).

Overview of Linux GUI (12.3.1.2)

Different Linux distributions ship with different software packages, but users decide what stays in their system by installing or removing packages. The graphical interface in Linux is composed of a number of subsystems that can also be removed or replaced by the user. While the details about these subsystems and their interactions are beyond the scope of this book, it is important to know that the Linux GUI as a whole can be easily replaced by the user. There are many Linux distributions, but this chapter focuses on Ubuntu Linux.

Ubuntu Linux uses Unity as its default GUI. One feature in the Linux GUI is the ability to have multiple desktops or workspaces, which allows the users to arrange the windows on a particular workspace.

Canonical has a website that simulates Unity’s user interface and also provides a tour through Unity’s main features. To experience Unity via Canonical’s website, visit http://tour.ubuntu.com/en.

As illustrated in Figure 12-52, there are five main components of the Ubuntu Unity desktop: launcher, dash search box, top menu bar, system notification menu, and lenses.

A dock, called the launcher, appears on the left side of the screen and serves as an application launcher and switcher. Right-click any application hosted on the launcher to access a short list of tasks the application can perform.

A multipurpose menu bar, called the dash search box, contains the currently running application, buttons to control the active window, and system controls and notifications.

A multipurpose menu bar, called the top menu bar, contains the currently running application, buttons to control the active window, and system controls and notifications.

Many important functions are located in the indicator menus at the top-right corner of the screen. This is called the system notification menu. Use the indicator menu to switch users, shut down the computer, control the volume level, or change network settings.

Lenses allow the user to fine-tune results.

Overview of macOS GUI (12.3.1.3)

Among the major differences between older versions of OS X and macOS is the addition of the Aqua GUI. Aqua was designed around the theme of water, with components resembling droplets and a deliberate use of reflection and translucency. The latest release of macOS at the time of writing is 10.1 Mojave. As illustrated in Figure 12-53, there are eight main components of the Apple Aqua desktop: Apple menu, application menu, menu bar, status menu, spotlight, desktop area, dock, and notification area.

The Apple menu enables you to access system preferences, software updates, power controls, and more.

The application menu displays the name of the active application in bold and the menu of the active application.

The menu bar contains the Apple menu, currently active application menus, status menus and indicators, Spotlight, and Notification Center.

The status menu displays the date and time and status of the computer and some features, such as Bluetooth and wireless.

Spotlight is a file system search feature in macOS. It can be used to find almost anything in the macOS. To start a new search, click the magnifying glass in the menu bar or press Cmd+Spacebar to bring up the search box. To change the document type being searched, go to Preferences. To specifically exclude locations from a Spotlight search, click the Privacy button to specify folders or drives to be excluded.

The desktop area, which is where most work is performed, is customizable. App windows open over the desktop, which can become covered by open windows. Mission Control gives you a simple view of everything that is open on the desktop. You can also open and work in multiple desktop spaces.

The dock displays thumbnails of frequently used applications and the running applications that are minimized. One of the important functions included in the Dock is Force Quit. By right-clicking a running application in the Dock, the user can choose Force Quit to close an unresponsive application. You can right-click an icon to display a menu of other actions to take, such as open or close an app, open a recent document, and so on.

The notification center icon allows the user to see all notifications.

The Apple Magic Mouse and the Magic Trackpad of a MacBook both support gestures to control the user interface. Gestures are finger movements on a trackpad or mouse that enable a user to scroll, zoom, and navigate desktop, document, and application content. Available gestures can be viewed and changed under System Preferences > Trackpad.

With macOS, Mission Control is a quick way to see everything that is currently open on a Mac. Mission Control can be accessed by using a three- or four-finger swipe-up gesture, depending on the touchpad or mouse settings. Mission Control allows you to organize apps on multiple desktops. To navigate the file system, macOS includes Finder, which is very similar to the Windows File Explorer.

Most Apple laptops do not have optical drives. To install software from optical media, you can use Remote Disk, an app that lets the user access a CD/DVD drive on another Mac or Windows computer. To set up Remote Disk, go to System Preferences > Sharing and then check the DVD or CD Sharing checkbox.

macOS also allows screen sharing. Screen sharing is a feature that enables other people using Macs to view your screen or even take control of your computer. This is very useful when you need help or want to help someone else.

Overview of Linux and macOS CLI (12.3.1.4)

In both Linux and macOS, the user can communicate with the operating system by using the command line interface (CLI). To add flexibility, options and switches that can be used with commands are usually preceded by the dash (-) character. The options and switches supported by a command are entered by the user along with the command.

Most operating systems include a graphical interface. Although a command line interface is still present, the OS often boots into the GUI by default, hiding the command line interface from the user. One way to access the command line interface in a GUI-based operating system is through a terminal emulator application. These applications provide user access to the command line interface and are often named using some variation of the word terminal. The terminal is separated from the kernel by the shell, as shown in Figure 12-54.

A program called a shell interprets the commands from the keyboard and passes them to the operating system. When a user logs into the system, the login program checks the username and password; if the credentials are correct, the login program starts the shell. From this point on, an authorized user can begin interacting with the OS through text-based commands.

Users interact with the kernel through a shell. Basically, the shell acts as an interface layer between the user and the kernel. The kernel is responsible for allocating CPU time and memory to processes. It also manages the file system and communications in response to system calls.

On Linux, popular terminal emulators are Terminator, eterm, xterm, konsole, and gnome-terminal. Figure 12-55 shows gnome-terminal.

macOS includes a terminal emulator called Terminal, and a number of third-party emulators are available as well. Figure 12-56 shows Terminal.

Linux Backup and Recovery (12.3.1.5)

The process of backing up data involves creating a copy (or multiple copies) of data for safekeeping. When the backup process is complete, the copy is called a backup. The primary goal of making backups is to be able to restore or recover data in case of failure. Gaining access to an earlier version of the data is often seen as a secondary goal of the backup process.

While backups can be achieved with a simple copy command, many tools and techniques exist to make the process automatic and transparent to the user.

Linux does not have a built-in backup tool. However, there are many commercial and open source backup solutions for Linux, such as Amanda, Bacula, Fwbackups, and Déjà Dup. Déjà Dup, shown in Figure 12-57, is an easy and efficient tool for backing up data. Déjà Dup supports a number of features, including local, remote, or cloud backup locations; data encryption compression; incremental backups; periodic scheduled backups; and GNOME desktop integration. It can also be used to restore from a particular backup.

macOS Backup and Recovery (12.3.1.6)

macOS includes a backup tool called Time Machine. With Time Machine, users choose an external drive to be used as a backup destination device and connect it to the Mac using USB, FireWire, or Thunderbolt. Time Machine prepares the disk to receive backups and, when the disk is ready, it performs incremental backups periodically.

If the user has not specified a Time Machine destination disk, Time Machine asks if the newly connected external disk should be used as the destination backup disk. Time Machine stores some backups on your Mac, and if the Time Machine backup disk is not available, you may be able to restore a backup directly from your Mac. This type of backup is called a local snapshot.

To enable Time Machine, go to System Preferences > Time Machine, slide the switch to On, and select the disk where the backups are stored, as shown in Figure 12-58. Clicking the Options button allows the user to select or unselect the files, folders, or drives to back up. By default, Time Machine performs hourly backups for the past 24 hours, daily backups for a month, and weekly backups for all previous months. When the destination backup drive becomes full, Time Machine removes the oldest backup files to free up space.

To restore data from Time Machine, make sure the destination backup disk is connected to the Mac and click Enter Time Machine in the Time Machine menu. A timeline on the right-hand side of the screen shows the available backups. Time Machine allows the user to restore the data to any previous version currently available in the destination backup disk.

Overview of Disk Utilities (12.3.1.7)

To help diagnose and solve disk-related problems, most modern operating systems include disk utility tools. Ubuntu Linux includes a disk utility called Disks. With Disks, users can perform the most common disk-related tasks, including partition management, mounting and unmounting, disk formatting, and query self-monitoring analysis and reporting technology (S.M.A.R.T.). macOS includes Disk Utility. In addition to supporting the main disk maintenance tasks, Disk Utility also supports Verify Disk Permissions and Repair Disk Permissions. Repair Disk Permissions is a common troubleshooting step in macOS. Disk Utility can also be used to back up disks to image files and perform an image recovery to disk from image files. These files contain the entire contents of a disk.

The following are a few common maintenance tasks that can be performed using disk utility software:

• Partition management: When working with computer disks, partitions may need to be created, deleted, or resized.

• Disk partition mounting or unmounting: On Unix-like systems, mounting a partition relates to the process of binding a partition of a disk or a disk image file (usually an .iso file) to a folder location.

• Disk formatting: Before a partition can be used by the user or the system, it must be formatted.

• Bad sector checking: When a disk sector is flagged as bad, it becomes harmless to the OS because it is no longer used to store data. The existence of many bad sectors could be an indicator of a failing disk. Disk utilities can salvage data stored in bad sectors by moving it to healthy disk sectors.

• S.M.A.R.T. attribute querying: S.M.A.R.T. can detect and report attributes about a disk’s health. The goal of S.M.A.R.T. is to anticipate disk failure so that the user can move the data to a healthy disk before the failing disk becomes inaccessible.

Scheduled Tasks (12.3.2.1)

Two tasks that should be scheduled and performed automatically are backups, shown in Figure 12-59, and disk checks.

Backups and disk checks are usually time-consuming tasks. An additional benefit of scheduled maintenance tasks is that it allows the computer to perform these tasks when no users are using the system. The CLI utility known as cron can schedule these tasks during off-peak hours.

In Linux and macOS, the cron service is responsible for scheduled tasks. cron runs in the background and executes tasks at specific dates and times. It uses a schedule table called a cron table that can be edited with the crontab command.

cron Table Format

The cron table is a plaintext file that has six columns, formatted as shown in Figure 12-60. A task is usually represented by a command, a program, or a script. To schedule a task, the user adds a row to the cron table. The new row specifies the minute, hour, day of the month, and the day of the week when the task should be executed by the cron service. When the specified date and time arrives, the task is executed.

Cron Table Fields

The center column of the cron table shows the data types acceptable for the fields, as shown in Figure 12-61.

Cron Table Example

The cron table shown in Figure 12-62 has two entries. The first entry tells the cron service to execute the myFirstTask script, located at /myDirectory/, on the first and fifteenth days of each month and also on Mondays, always at midnight (0h0m). The second entry shows that the cron service should execute mySecondTask script, also located at /myDirectory/, every Thursday at 2h37m in the morning.

To create or edit the cron table, use the crontab -e command from a terminal.

To list the current cron table, use the crontab -l command.

To remove the current cron table, use the crontab -r command.

Operating System Updates (12.3.2.2)

Despite continued efforts to create a perfectly secure operating system, vulnerabilities still exist. When a vulnerability is found, it can be exploited with a virus or other malicious software.

Measures can be taken to help prevent malicious software from infecting a computer system. The most common of these measures are operating system updates, firmware updates, antivirus, and anti-malware. Also known as patches, OS updates are released periodically by OS companies to address any known vulnerabilities in their operating systems. While companies have update schedules, the release of unscheduled OS updates is common when a major vulnerability is found in OS code. Modern operating systems alert the user when updates are available for download and installation, but the user can check for updates at any time. Figure 12-63 shows an update alert window for Apple macOS.

Security (12.3.2.3)

Digital assets are very valuable, and the theft of these assets are a major threat to users and organizations. Proper security practices include methods of protecting credentials that allow access to these assets.

Security Credentials Service on Ubuntu

GNOME Keyring, shown in Figure 12-64, is a security credentials manager for Ubuntu Linux. To access GNOME Keyring on Ubuntu Linux, select Dash then search for Key > Passwords and Keys.

Security Credentials Service on macOS

Keychain, shown in Figure 12-65, is a security credentials manager for macOS. To access Keychain on macOS, select Applications > Utilities > Keychain Access.

12.3.2.4 Check Your Understanding - Linux and macOS Best Practices

Refer to the online course to complete this activity.

The ls –l Command Output (12.3.3.3)

In the following section you will examine the ls –l command output, as demonstrated in Figure 12-66.

Table 12-1 describes each of the components of this output.

Basic Unix File and Directory Permissions (12.3.3.4)

To organize the system and reinforce boundaries within the system, Unix uses file permissions. File permissions are built into the file system structure and provide a mechanism to define permissions to every file and directory. Every file and directory on a Unix system carries permissions that define the actions that the owner, the group, and others can do with the file or directory.

The only user who can override file permissions in Unix is the root user. Having the power to override file permissions means the root user can write to any file. Because everything in Unix is treated as a file, the root user has full control over the Unix operating system. Root access is often required to perform maintenance and administrative tasks.

Review the different permission values shown in Figure 12-67. Note how file and directory access is affected by the permissions.

Table 12-2 provides a summary of the Unix file permissions.

Table 12-3 summarizes the Unix directory and file permissions.

Linux Administrative Commands (12.3.3.7)

Administrators use the terminal, shown in Figure 12-68, to monitor and control users, processes, and IP addresses and to carry out other tasks. Certain commands can be executed by users without any special privileges while others require elevated privileges.

To get to the terminal in an Ubuntu distribution, click Activities in the upper-left corner and type terminal. How you open the terminal in other Linux distributions varies depending on the interface.

passwd

The passwd command, shown in Figure 12-69, allows users to change their own passwords at the terminal. To change a password, the user must know his or her current password. For security reasons, neither the password characters nor asterisks are displayed while the user types the password. The passwd command is often confused with the pwd command, which stands for print working directory.

ps

The ps command, shown in Figure 12-70, allows users to monitor their own processes. If the ps command is used without specifying options, it only shows the programs that are running in the current terminal. The second use of the ps command shown in Figure 12-70 includes the -e option, indicating everything. The output of the command is piped to the grep command to search for output lines that match the word gnome (pronounced “Gee-Nome”).

kill

The kill command, shown in Figure 12-71, allows users to end the processes that they have started. In this example, Firefox was started in the background using the ampersand (&). The kill command was used to abruptly end the Firefox process. Use man kill to view useful options for the kill command.

ifconfig

The ifconfig command, shown in Figure 12-72, is used in much the same way as the Windows ipconfig command. Although it is referenced in the CompTIA A+ objectives, this command has been deprecated, and the ip address command should be used instead.

iwconfig

The iwconfig command, shown in Figure 12-73, is one of many wireless commands that start with the letters iw. The iwconfig command allows users to set and view their wireless settings. In the example shown in Figure 12-73, no wireless connections are being used.

chmod

The chmod command, shown in Figure 12-74, allows users to change the permissions of files that they own. In the example shown in Figure 12-74, a script is made executable using octal mode, and it is reverted using reference mode.

Linux Administrative Commands Requiring Root Access (12.3.3.8)

Some commands can be used without special privileges. Other commands require root access some of the time or all of the time, as shown in Figure 12-75. Typically, a user can manipulate the files within his or her own home directory, but changing files and settings throughout the server requires either sudo (superuser DO) or root access.

sudo

The sudo command, shown in Figure 12-76, grants a user root access without actually changing the user’s profile. The access is granted for a limited time but only if the user is listed in the /etc/sudoers file. In the example shown in Figure 12-76, sudo is needed to kill a process.

chown

The chown command, shown in Figure 12-77, allows a user to switch both the owner and the group of a file or files. After using the su or sudo command, users may see files that don’t belong to them in their home directories. Use the -R (recursive) option with the chown command to revert all files in a user’s home directory back to the user.

apt-get

The apt-get command, shown in Figure 12-78, is used to install and manage software on Debian-based Linux distributions. There are many options available for this command, and you can examine them by simply typing apt. The apt-get command has been deprecated in favor of simply using apt.

shutdown

The shutdown command, shown in Figure 12-79, is used to halt and reboot the operating system. It can also warn users of an impending shutdown and schedule a shutdown to occur in the future. In a multi-user system, regular users do not have the rights to shut down the system.

dd

The dd (disk duplicate) command, shown in Figure 12-80, is used to copy files and partitions and to create temporary swap files. The dd command should be used with extreme caution.

12.3.3.9 Check Your Understanding - Administrative Commands

Refer to the online course to complete this activity.

12.3.3.10 Syntax Checker - File Ownership and Permission

Refer to the online course to complete this activity.

The Six Steps of the Troubleshooting Process (12.4.1.1)

The six steps of the troubleshooting process are:

Step 1. Identify the problem.

Step 2. Establish a theory of probable cause.

Step 3. Test the theory to determine the cause.

Step 4. Establish a plan of action to resolve the problem and implement the solution.

Step 5. Verify full system functionality and, if applicable, implement preventive measures.

Step 6. Document findings, actions, and outcomes.

Identify the Problem (12.4.1.2)

When troubleshooting problems with a mobile device, find out if the device is under warranty. If it is, it can often be returned for repair or exchange. If the device is no longer under warranty, determine whether repairing the device would be cost-effective. To determine the best course of action, compare the cost of the repair with the cost of replacing the mobile device. Because mobile devices tend to change rapidly in design and functionality, repairing them is often more expensive than replacing them. For this reason, mobile devices are usually replaced.

Mobile device problems can result from a combination of hardware, software, and network issues. Mobile technicians must be able to analyze a problem and determine the cause of the error to repair the mobile device. This process is called troubleshooting.

The first step in the troubleshooting process is to identify the problem. Table 12-4 shows a list of open-ended and closed-ended questions to ask the customer for mobile device operating systems and on Linux and macOS.

Establish a Theory of Probable Cause (12.4.1.3)

After you have talked to the customer, you can establish a theory of probable cause. Table 12-5 shows a list of some common probable causes for problems with mobile device operating systems, Linux, and macOS.

Test the Theory to Determine the Cause (12.4.1.4)

After you have developed some theories about what is wrong, test your theories to determine the cause of the problem. When the theory is confirmed, you can determine the steps to resolve the problem. Table 12-6 shows a list of quick procedures that can determine the exact cause of the problem or even correct the problem. If a quick procedure corrects the problem, you can then verify full system functionality. If a quick procedure does not correct the problem, you might need to research the problem further to establish the exact cause.

Establish a Plan of Action to Resolve the Problem and Implement the Solution (12.4.1.5)

When you have determined the exact cause of a problem, establish a plan of action to resolve the problem and implement the solution. Table 12-7 shows some sources you can use to gather additional information to resolve an issue.

Verify Full System Functionality and, if Applicable, Implement Preventive Measures (12.4.1.6)

After you have corrected the problem, you verify full functionality and, if applicable, implement preventive measures. Table 12-8 shows a list of the steps to verify the solution.

Document Findings, Actions, and Outcomes (12.4.1.7)

In the final step of the troubleshooting process, you must document your findings, actions, and outcomes. Table 12-9 lists the tasks required to document the problem and the solution.

Common Problems and Solutions for Mobile Operating Systems (12.4.2.1)

Table 12-10 outlines how you can use the first step of the troubleshooting process (identify the problem) to determine possible solutions to common problems for mobile operating systems.

Common Problems and Solutions for Mobile OS Security (12.4.2.2)

Table 12-11 outlines how you can use the first step of the troubleshooting process (identify the problem) to determine possible solutions to common problems for mobile operating system security.

Common Problems and Solutions for Linux and macOS Operating Systems (12.4.2.3)

Table 12-12 outlines how you can use the first step of the troubleshooting process (identify the problem) to determine possible solutions to common problems for Linux and macOS operating systems.