Содержание
Аннотация
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.
openSUSE and Tablet PCs | |
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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 Глава 22, 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 Глава 19, Power Management.
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:
This includes IP address assignment, name resolution, Internet connectivity and connectivity to other networks.
A current database of available printers and an available print server must be present, depending on the network.
As with printing, the list of the corresponding servers must be current.
If your laptop is temporarily connected to a projector or an external monitor, different display configurations must be available.
openSUSE offers several ways of integrating laptops into existing operating environments:
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 mobile broadband (such as GPRS, EDGE, or 3G), 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 Раздел 21.4, «Using KNetworkManager» and Раздел 21.5, «Using GNOME NetworkManager Applet».
Таблица 18.1. 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.
DNS configuration and various types of network connections | |
---|---|
If you travel frequently with your laptop and change different types
of network connections, NetworkManager works fine when all DNS addresses are
assigned correctly assigned with DHCP. If some of your connections
use static DNS address(es), add it to the
|
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 also be used to install a system, minimizing the effort of searching for a suitable installation source. Find detailed information about SLP in Глава 10, 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:
is an application which lets you adjust energy saving related behavior of the KDE desktop. You can typically access it via the tray icon, which changes according to the type of the current power supply. Other way to open its configuration dialog is through the : + + + .
Click the
tray icon to access options to configure its behavior. You can choose one of five displayed power profiles which best fits 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. Click to open a more complex configuration screen. Here you can edit individual profiles and set advanced power management options and notifications, such as what to do when the laptop lid has been closed, or when the battery charge is low.(also called ) gathers measurable system parameters into one monitoring environment. It presents the output information in 2 tabs by default. gives detailed information about currently running processes, such as CPU load, memory usage, or process ID number and nice value. The presentation and filtering of the collected data can be customized — to add a new type of process information, left-click on the process table header and choose which column to hide or add to the view. It is also 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 environment use
and .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:
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. 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
system-wide MTA postfix or sendmail to receive reliable feedback
about unsent mail.
There are several utilities suitable for synchronizing data between a laptop and a workstation. One of the most widely used is a command-line tool called rsync. For more information, see Глава 23, Copying and Sharing Files.
As well as connecting to a home or office network with a cable, a laptop can also use wireless connection to access other computers, peripherals, cellular phones or PDAs. Linux supports three types of wireless communication:
With the largest range of these wireless technologies, WLAN is the only one suitable for the operation of large and sometimes even spatially separate 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 Глава 20, Wireless LAN.
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 a 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 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:
Always physically secure your system against theft whenever possible. Various securing tools (like chains) are available in retail stores.
Use biometric authentication in addition to standard authentication via login and password. openSUSE supports fingerprint authentication. For more details, see Глава 7, Использование сканера отпечатков пальцев (↑Руководство по безопасности).
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 Глава 10, Шифрование файлов и разделов (↑Руководство по безопасности). Another possibility is to create encrypted home directories when adding the user with YaST.
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. |
Any transfer of data should be secured, no matter how the transfer is done. Find general security issues regarding Linux and networks in Глава 1, Безопасность и конфиденциальность (↑Руководство по безопасности). Security measures related to wireless networking are provided in Глава 20, Wireless LAN.
openSUSE supports the automatic detection of mobile storage devices over FireWire (IEEE 1394) or USB. The term mobile storage device applies to any kind of FireWire or USB hard disk, USB flash drive, or digital camera. These devices are automatically detected and configured as soon as they are connected with the system over the corresponding interface. The file managers of both GNOME and KDE offer flexible handling of mobile hardware items. To unmount any of these media safely, use the (KDE) or (GNOME) feature of either file manager.
As soon as an external hard disk is correctly recognized by the
system, its icon appears in the file manager. Clicking the icon
displays the contents of the drive. It is possible to create folders
and files here and edit or delete them. To rename a hard disk from the
name it had been given by the system, select the corresponding menu
item from the menu that opens when the icon is right-clicked. This
name change is limited to display in the file manager. The descriptor
by which the device is mounted in /media
remains
unaffected by this.
These devices are handled by the system just like external hard disks. It is similarly possible to rename the entries in the file manager.
Digital cameras recognized by the system also appear as external drives in the overview of the file manager. KDE allows reading and accessing the pictures at the URL camera:/ . The images can then be processed using digiKam or f-spot. For advanced photo processing, use GIMP.
A desktop system or a laptop can communicate with a cellular phone via Bluetooth or IrDA. Some models support both protocols and some only one of the two. The usage areas for the two protocols and the corresponding extended documentation has already been mentioned in Раздел 18.1.3.3, «Wireless Communication». The configuration of these protocols on the cellular phones themselves is described in their manuals.
The support for synchronizing with handheld devices manufactured by Palm, Inc., is already built into Evolution and Kontact. Initial connection with the device is easily performed with the assistance of a wizard. Once the support for Palm Pilots is configured, it is necessary to determine which type of data should be synchronized (addresses, appointments, etc.).
A more sophisticated synchronization solution is available with the
program opensync
(see packages libopensync, msynctool
and the respective plug-ins for the different devices).
The central point of reference for all questions regarding mobile devices and Linux is http://tuxmobil.org/. Various sections of that Web site deal with the hardware and software aspects of laptops, PDAs, cellular phones and other mobile hardware.
A similar approach to that of http://tuxmobil.org/ is made by http://www.linux-on-laptops.com/. Information about laptops and handhelds can be found here.
SUSE maintains a mailing list in German dedicated to the subject of laptops. See http://lists.opensuse.org/opensuse-mobile-de/. On this list, users and developers discuss all aspects of mobile computing with openSUSE. Postings in English are answered, but the majority of the archived information is only available in German. Use http://lists.opensuse.org/opensuse-mobile/ for English postings.
Information about OpenSync
is available on
http://en.opensuse.org/OpenSync.