How Linux helps Nokia770

Linux assists Nokia770-general Linux technology-Linux programming and kernel information. The following is a detailed description. Based on Linux®Nokia 770 Internet tablet is a fascinating thing for Linux enthusiasts. Although it does not have most personal information management (PIM) programs that people expect from handheld computers, however, its new advantages in the development environment make it highly favored by these enthusiasts and professional embedded developers.
The release of Nokia 770 in the Linux Industry has aroused cheers. 770 different from the previous Zaurus, it is also very different from the Pocket PC or Palm system. It does not provide the personal information management (PIM) function; in fact, it does not directly provide the features required by common PDAs. Instead, it is more like an Internet tablet that provides applications such as Web browsers and e-mail clients ".

Nokia recently released an update package for 770 software, which is more friendly for users who want to study the device. In earlier versions, you must enter R & D mode to obtain the root access permission. Version 1.05 makes this problem easier to solve.

Nokia 770 has two storage devices available. One is an internal flash device (formatted as a JFFS2 file system), and the other is an inserted card (formatted as a FAT file system ). The connection method of 770 is very interesting. When connecting through USB, this device is used as a large storage device by default. 770 of internal storage will not be made public in this way; on the contrary, the inserted card is used as a general USB storage device for upstream computers, so that files can be transmitted simply. When 770 is connected via USB in this way, the card will be detached from 770 to prevent data crash. This method provides good access to files on the device.

To a large extent, a device does not require much manual configuration; it can be connected to a Bluetooth phone or wireless network. This connection can be automatically implemented or implemented with a small amount of user intervention. Linux-based systems have developed significantly in the Automatic Network Configuration Technology.

Installation overview

The 770 installation is built around BusyBox like similar devices. The startup scripts are quite standard Debian scripts with complete README files. The interesting part is the user interface and development tools, which are significantly improved compared with the original Zaurus environment. The maemo.org page provides comprehensive support for developers (see the links in references ).

Compared with Linux-based devices that I have seen before, 770 of the difference is that the support for developers is more effective and deeper. 770 does not solve all the problems well (Fortunately, Web browsing is an exception ). However, Nokia seems to want to consider the potential of community development as one of the main advantages of this machine. Development tools also focus more on general enthusiasts than professional developers. You can download a tool to load a new ROM image and set a special device identifier (such as R & D mode.

This feature triggers a large number of interesting development projects. For example, like most tablet or PDA devices, 770 has a major flaw in text input: Even if you like keyboard or handwriting recognition, it occupies a large place on the screen, this is too costly for a device with only 4 inch screens. Now you can use a Bluetooth or USB keyboard on 770. The situation is much better (for more information, see the sidebar ).

Access permission

In earlier versions of 770, you must use the flasher tool to switch the device to R & D mode and then run the gainroot script. This script is interesting in itself, as shown in Listing 1.


Listing 1. gainroot script
#! /Bin/sh-e
Trap exit SIGHUP SIGINT SIGTERM
PATH =/bin:/usr/bin:/sbin:/usr/sbin
MODE = '/usr/sbin/chroot/mnt/initfs cal-tool -- get-rd-Mode'
If [x $ MODE = xenabled]
Then
Echo "Root shell enabled"
/Bin/sh
Else
Echo "Enable RD mode if you want to break your device"
Fi





The default sudoers file allows anyone to run this script using the sudo command; if your 770 is in R & D mode now, you will get a shell; otherwise, you will see a humorous warning message.

The latest version provides a simpler option: you can log on to the system using ssh as the root user. This requires downloading a third-party dropbear package, and then using ssh as the root user to log on to the system. The password is rootme. The default password that allows root login can be seen everywhere, which is too simple and straightforward. If you have installed an ssh server, make sure to change your root password. You have not modified? Really? Modify it. A common solution is to set the user's password, configure/etc/sudoers, and then run passwd-l root to completely disable root login.

The reason we want to leave this topic out is to explain that although some vendors can provide some minimal subsets of Linux and strictly protect them, Nokia now provides us with a compiler. For the moment, this device is not a consumer for most people; it is only a "toy box. There are a lot of interesting things about how to find a Linux with complete features suitable for use on such a small device.

Desktop System Problems

770 installation does not determine whether the system is an embedded system or a fully functional Desktop Linux. In earlier versions, a system image is provided, and all files installed in the image are not controlled by the package management system. In previous versions, the Package Manager provides more than 900 packages, some of them are optional, and some are not, as shown in Listing 2.


Listing 2. Starting with a long list
# Dpkg-l
Desired = Unknown/Install/Remove/Purge/Hold
| Status = Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/Err? = (None)/Hold/Reinst-required/X = both-problems (Status, Err: uppercase = bad)
|/Name Version Description
++-============================================= ==============================================
Ii adduser 3.51 Add and remove users and groups
Ii apt 0.6.42.3osso13 Advanced front-end for dpkg
Ii archtunjo 0.0.8-4 the D-BUS wrapper for games
Ii autoipd 0.9.6-1osso9 Autoipd from Howl
Ii base-files 3.1.osso2 Debian base system miscellaneous files
Ii base-passwd 3.5.7.osso1 Debian base system master password and group
Ii bluez-utils 2.25-cvs200605 Bluetooth tools and daemons





This provides the foundation for more flexible installation, and sometimes you may want to free up some space to install other files-not because the system may soon have no space. Most of the large files used on mobile devices are stored on removable cards, rather than on primary storage.

In general, we need to delete some less useful programs or scripts. For example, glibc. THE sh script is responsible for warning glibc compatibility requirements on the AMD64 system. On 770, it is obviously unnecessary (it actually involves the ARM system; they need kernel versions 2.4 or later. The 2.6.16 kernel in the version I have seen may be fine ). In addition, every system I have seen has something like this. In practice, it may be very troublesome and not worth trying to delete these useless things.

Development

770 of software development environments are relatively new, but 770 of end users cannot see it, because these development tools are not actually loaded to 770 devices, but run on a workstation or PC. About three years ago, I wrote something about cross-compilation for Sharp Zaurus (see the link in references ). This process is very tricky. 770 uses a new cross-compilation environment named Scratchbox, which is developed by Nokia. This tool has many improvements. It provides an environment where binary files on the target system can run in the Cross-development process (in simulation mode ). The final result is that all the troubles and confusions used to solve the poorly written portability tests are gone; what you get is the performance of the host system (including local execution of the compiler tool chain) and the Behavior capability of the target system.

Although these tools are still in the early stages of development, they are stable, powerful, and actively maintained. There may be a long way to develop tools for a variety of other systems. In addition, a good cross-compilation environment has eliminated some drawbacks of traditional usage, this can help reduce the inconvenience caused by the absence of too much memory and CPU for large-scale software compilation.

Mandatory comparison

From 770, we can see that it has learned a lot from Zaurus. As I mentioned earlier, the lack of physical keyboards has attracted many external development efforts. A more subtle improvement is the amount of available memory. Although the memory is more than 770 compared with the previous devices, it can easily consume up to of the memory. It can be helpful even if you only have a little more memory. On the other hand, full-screen video playback cannot be avoided. devices that provide this function will be impressed.

770 does not have some expansion options like some PDA devices (using the CompactFlash and Secure Digital card slots ). Its only expansion slot uses a simplified SD card, which is undoubtedly perfect for this very crowded device. On the other hand, few PDA devices can be configured to work as USB Host devices; if you are willing to spend some time and effort, 770 or even use a USB hard disk.

Because 770 is a handheld device, people will inevitably compare it with various handheld devices. 770 is not a PDA. It is an Internet widget. The Opera Web Browser provided in 770 is not available in general handheld devices. 770 there is no PIM application that users expect from PDAs. However, many devices designed to target PDAs are also used in other applications, for example, Web and email access. In many cases, compared to such devices, the performance of 770 is very good, but it would be better to better support the keyboard-for example, to support the traditional IR keyboard.

Nokia has made a lot of efforts to enhance the friendliness of fans and players by 770, but the default installation does not contain any shell, which is quite different from Zaurus. Presented to users is more like a simplified Internet kiosk terminal than a desktop workstation. Similar to TiVo, to effectively use the basic features of 770, we do not need to understand or care that we are running the Linux system. However, unlike TiVo, 770 users are welcome to use Linux to add their own features.

770 development goals

During my research into this article, I read a lot of comments about 770. I feel that many people do not know what 770 is. Everyone claims to have a tablet-based Web browser, but many people do not know exactly what they want to use it.

770 provides wireless and bluetooth access capabilities, which makes it very eye-catching as a device for searching content on the Web. It also has the potential to be used to develop custom applications. For example, it can become an excellent wireless network sniffer.

Although the goal of 770 is not clear yet, Nokia has done a lot of research on it. They have developed a new set of cross-compilation architectures, which has been widely used in 770. The developer-friendly environment seems to have brought many hackers in. However, the feedback and patches provided by the developers will inevitably help to continuously improve the development environment. Even if it won't directly achieve great success, 770 has made great contributions to the field of Embedded Linux development. In the end, it will make Linux-based devices better and cheaper in the future.