6 processes and precautions for system transplantation based on 2.6 kernel

Upgrade embedded system

If the user installs a commercial Linux package similar to TimeSysLinux2.6, it can provide a complete set of core Linux components that have been verified and can work together. However, even in these cases, not all changes made by users on the existing system were manually ported to the new SDK (System Design Kit). Generally, transplanting a system based on the 2.6 kernel includes the following process:

◆Upgrade all mandatory package software to adapt to the compiler and build the system environment on any desktop system associated with the embedded system.

◆Upgrade all mandatory software packages to accommodate all cross-compilers used to develop application software for the target system.

◆Migrate the customized kernel settings to the 2.6 kernel.

◆Change all hardware drivers to drivers available under the 2.6 kernel.

◆Upgrade all mandatory package software to adapt to the application software and tool software used for the existing root file system or initial RAMc disk.

◆Migrate all system management and setting changes from the existing root file system to the new root file system under the 2.6 kernel.

◆Migrate customized application software from the existing root file system to the new root file system under the 2.6 kernel.

Initial RAMc disk and root file system

The file system is the area where the storage medium for the system to read and write data is located. Linux systems use file systems for a variety of purposes, including storage systems, user files and file directories, and as swap space to support virtual video memory. The most important file system in the Linux system is the root file system, which users can install through the "/" directory.

The first step to load the kernel into video memory is to start the Linux system. When many Linux systems are started, the kernel will use a file system that has been stored in the video memory-the initial RAMc disk. The initial RAMc disk is not compressed in any way and can be directly loaded into the video memory, but it can be used as a temporary root file system during the startup process. Users can execute commands through the initial RAMc disk, or they can download the linux tutorial before using the system hardware and pre-load the modules required for subsequent steps. In desktop systems, the initial RAMc disk is almost a universal transition process. In an embedded Linux system with sufficient video memory, the initial RAMc disk is the root file system actually used when the Linux system is running.

TimeSys's TargetConfigurator tool software, as a member of the TimeStormLinux development kit, can greatly simplify the creation process of the initial RAMc disk. The initial RAMc disk created by TargetConfigurator contains all system software required for startup time and runtime. TargetConfigurator can also simplify the process of downloading applications to the initial RAM disk used as the root file system and to file systems such as JFFS2 or ext3 for different types of storage devices.

TimeSysLinux2.6ReferenceDistributions contain pre-assembled initial RAMc disks for all supported platforms and architectures. Most Linux packages provide some large programs (such as mkinitrd for RedHatLinux) to facilitate users to build their own initial RAMc disk. However, if the user is migrating to a kernel based on 2.6, but wants to continue to use the initial RAMc disk that the user has programmed, then the user needs to verify its contents for compatibility with the new kernel.

Users can install the initial RAMc disk as loopback hardware in a Linux system and thus verify it. In fact, loopback hardware is a kind of virtual hardware linux kernel porting, and the Linux system can access it like real hardware. Before installing the initial RAMc disk, the user must ensure that the current kernel supports loopback hardware devices. For the 2.6 kernel, users can provide support for loopback hardware through the DeviceDrivers→BlockDevices→Loopbackdevicesupport option in the kernel settings compiler. Under the 2.4 kernel, this option is in BlockDevices→Loopbackdevicesupport.

In desktop Linux systems using the GRUB boot program, the system's initial RAMc disk is generally stored as a separate kernel external file. This file is usually found in the /boot directory and can be identified in the GRUB configuration file (/etc/grub.conf). In most embedded systems, the initial RAMc disk is created as a file external to the kernel, and is bundled with the kernel as the last step in the kernel build.

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