Abstract
Mobile computing is mostly associated with laptops, PDAs and cellular phones (and the data exchange between them). Mobile hardware components, such as external hard disks, flash drives, or digital cameras, can be connected to laptops or desktop systems. A number of software components are involved in mobile computing scenarios and some applications are tailor-made for mobile use.
The hardware of laptops differs from that of a normal desktop system. This is because criteria like exchangeability, space requirements and power consumption must be taken into account. The manufacturers of mobile hardware have developed standard interfaces like PCMCIA (Personal Computer Memory Card International Association), Mini PCI and Mini PCIe that can be used to extend the hardware of laptops. The standards cover memory cards, network interface cards, ISDN (and modem cards) and external hard disks.
![[Tip]](admon/tip.png) | openSUSE and Tablet PCs |
|---|---|
openSUSE also supports Tablet PCs. Tablet PCs come with a touchpad/digitizer that allows you to use a digital pen or even fingertips to edit data right on the screen instead of using mouse and keyboard. They are installed and configured much like any other system. For a detailed introduction to the installation and configuration of Tablet PCs, refer to Chapter 33, Using Tablet PCs. | |
The inclusion of energy-optimized system components during laptop manufacturing contributes to their suitability for use without access to the electrical power grid. Their contribution towards conservation of power is at least as important as that of the operating system. openSUSE® supports various methods that influence the power consumption of a laptop and have varying effects on the operating time under battery power. The following list is in descending order of contribution towards power conservation:
Throttling the CPU speed.
Switching off the display illumination during pauses.
Manually adjusting the display illumination.
Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external mouse, unused PCMCIA cards, WLAN, etc.).
Spinning down the hard disk when idling.
Detailed background information about power management in openSUSE is provided in Chapter 31, Power Management. For more information desktop specific power management, see the Section “Controlling Your Desktop’s Power Management” (Chapter 2, Working with Your Desktop, ↑GNOME User Guide) on how to use the GNOME Power Manager. More information about the KDE power management applet is available at Chapter Controlling Your Desktop’s Power Management (↑KDE User Guide).
Your system needs to adapt to changing operating environments when used for mobile computing. Many services depend on the environment and the underlying clients must be reconfigured. openSUSE handles this task for you.
The services affected in the case of a laptop commuting back and forth between a small home network and an office network are:
- Network
This includes IP address assignment, name resolution, Internet connectivity and connectivity to other networks.
- Printing
A current database of available printers and an available print server must be present, depending on the network.
- E-Mail and Proxies
As with printing, the list of the corresponding servers must be current.
- X (Graphical Environment)
If your laptop is temporarily connected to a projector or an external monitor, the different display configurations must be available.
openSUSE offers several ways of integrating laptops into existing operating environments:
- NetworkManager
NetworkManager is especially tailored for mobile networking on laptops. It provides a means to easily and automatically switch between network environments or different types of networks, such as wireless LAN and ethernet. NetworkManager supports WEP and WPA-PSK encryption in wireless LANs. It also supports dial-up connections (with smpppd). Both desktop environments (GNOME and KDE) include a front-end for NetworkManager. For more information about the desktop applets, see Section “Using KNetworkManager” (Chapter 5, Using NetworkManager, ↑Start-Up) and Section “Using GNOME NetworkManager Applet” (Chapter 5, Using NetworkManager, ↑Start-Up).
Table 30.1. Use Cases for NetworkManager
My computer…
Use NetworkManager
is a laptop
Yes
is sometimes attached to different networks
Yes
provides network services (such as DNS or DHCP)
No
only uses a static IP address
No
Use the YaST tools to configure networking whenever NetworkManager should not handle network configuration.
- SCPM
SCPM (system configuration profile management) allows storage of arbitrary configuration states of a system into a kind of “snapshot” called a profile. Profiles can be created for different situations. They are useful when a system is operating in changing environments (home network, office network). It is always possible to switch between profiles. To get SCPM up and running on your system, install the package
scpm. Enable SCPM using the YaST Profile Management module and configure the users that should be allowed to switch profiles without the need of entering therootpassword. Determine whether profile changes should survive a system reboot or whether they should be discarded upon shutdown. Make sure all resource groups (i.e. services like network and printer, for example) are active. Proceed to creating actual profiles using scpm command line tool. Refer to thescpmman page for details. Create profiles for all the different setups you want to use this system in. Switching between profiles can either be done on the running system via scpm switchPROFILENAMEor at system boot time via the F3 key. When switching profiles, SCPM automatically adjusts your system configuration to the new environment laid out in the profile you have chosen.Under KDE, a GUI for
scpmis available. Make sure the packagekscpmis installed. Start the via ++ from the KDE Main Menu. The Profile Management tools lets you create and manage profiles. You can switch profiles by using the Profile Management applet in the system tray.- SLP
The service location protocol (SLP) simplifies the connection of a laptop to an existing network. Without SLP, the administrator of a laptop usually requires detailed knowledge of the services available in a network. SLP broadcasts the availability of a certain type of service to all clients in a local network. Applications that support SLP can process the information dispatched by SLP and be configured automatically. SLP can even be used for the installation of a system, sparing the effort of searching for a suitable installation source. Find detailed information about SLP in Chapter 22, SLP Services in the Network.
There are various special task areas in mobile use that are covered by dedicated software: system monitoring (especially the battery charge), data synchronization, and wireless communication with peripherals and the Internet. The following sections cover the most important applications that openSUSE provides for each task.
Two KDE system monitoring tools are provided by openSUSE:
- KPowersave
KPowersave is an applet that displays the state of the rechargeable battery in the control panel. The icon adjusts to represent the type of power supply. When working on AC power, a small plug icon is displayed. When working on batteries, the icon changes to a battery.
Right-click the KPowersave tray icon to access options to configure KPowersave behavior. You can choose one of four listed schemes, according to your needs. For example, the scheme disables the screen saver and the power management in general, so that your presentation is not interrupted by system events. You can also tell the system what to do if, for example, you close the laptop lid or press the power button.
- KSysguard
KSysguard is an independent application that gathers all measurable parameters of the system into one monitoring environment. KSysguard has monitors for ACPI (battery status), CPU load, network, partitioning and memory usage. It can also watch and display all system processes. The presentation and filtering of the collected data can be customized. It is possible to monitor different system parameters in various data pages or collect the data of various machines in parallel over the network. KSysguard can also run as a daemon on machines without a KDE environment. Find more information about this program in its integrated help function or in the SUSE help pages.
In the GNOME desktop, use GNOME Power Management Preferences and System Monitor.
When switching between working on a mobile machine disconnected from the network and working at a networked workstation in an office, it is necessary to keep processed data synchronized across all instances. This could include e-mail folders, directories and individual files that need to be present for work on the road as well as at the office. The solution in both cases is as follows:
- Synchronizing E-Mail
Use an IMAP account for storing your e-mails in the office network. Then access the e-mails from the workstation using any disconnected IMAP–enabled e-mail client, like Mozilla Thunderbird Mail, Evolution, or KMail as described in GNOME User Guide (↑GNOME User Guide) and KDE User Guide (↑KDE User Guide). The e-mail client must be configured so that the same folder is always accessed for
Sent messages. This ensures that all messages are available along with their status information after the synchronization process has completed. Use an SMTP server implemented in the mail client for sending messages instead of the systemwide MTA postfix or sendmail to receive reliable feedback about unsent mail.- Synchronizing Files and Directories
There are several utilities suitable for synchronizing data between a laptop and a workstation. For detailed information, refer to Chapter 34, Copying and Sharing Files.
As well as connecting to a home or office network with a cable, a laptop can also wirelessly connect to other computers, peripherals, cellular phones or PDAs. Linux supports three types of wireless communication:
- WLAN
With the largest range of these wireless technologies, WLAN is the only one suitable for the operation of large and sometimes even spatially disjointed networks. Single machines can connect with each other to form an independent wireless network or access the Internet. Devices called access points act as base stations for WLAN-enabled devices and act as intermediaries for access to the Internet. A mobile user can switch among access points depending on location and which access point is offering the best connection. Like in cellular telephony, a large network is available to WLAN users without binding them to a specific location for accessing it. Find details about WLAN in Chapter 32, Wireless LAN.
- Bluetooth
Bluetooth has the broadest application spectrum of all wireless technologies. It can be used for communication between computers (laptops) and PDAs or cellular phones, as can IrDA. It can also be used to connect various computers within range. Bluetooth is also used to connect wireless system components, like a keyboard or mouse. The range of this technology is, however, not sufficient to connect remote systems to a network. WLAN is the technology of choice for communicating through physical obstacles like walls.
- IrDA
IrDA is the wireless technology with the shortest range. Both communication parties must be within viewing distance of each other. Obstacles like walls cannot be overcome. One possible application of IrDA is the transmission of a file from a laptop to a cellular phone. The short path from the laptop to the cellular phone is then covered using IrDA. The long range transport of the file to the recipient of the file is handled by the mobile network. Another application of IrDA is the wireless transmission of printing jobs in the office.
Ideally, you protect data on your laptop against unauthorized access in multiple ways. Possible security measures can be taken in the following areas:
- Protection against Theft
Always physically secure your system against theft whenever possible. Various securing tools (like chains) are available in retail stores.
- Strong Authentication
Use biometric authentication in addition to standard authentication via login and password. openSUSE supports fingerprint authentication. For more details, see Chapter Using the Fingerprint Reader (↑Security Guide).
- Securing Data on the System
Important data should not only be encrypted during transmission, but also on the hard disk. This ensures its safety in case of theft. The creation of an encrypted partition with openSUSE is described in Chapter Encrypting Partitions and Files (↑Security Guide). Another possibility is to create encrypted home directories when adding the user with YaST.
![[Important]](admon/important.png)
Data Security and Suspend to Disk Encrypted partitions are not unmounted during a suspend to disk event. Thus, all data on these partitions is available to any party who manages to steal the hardware and issue a resume of the hard disk.
- Network Security
Any transfer of data should be secured, no matter how the transfer is done. Find general security issues regarding Linux and networks in Chapter Security and Confidentiality (↑Security Guide). Security measures related to wireless networking are provided in Chapter 32, Wireless LAN.