The minimum root file is successfully created in Linux.

This article explains some problems that may occur when learning the Linux operating system, such as how to create a minimum root file system for Linux, I hope you will learn how to build a minimum root file system in Linux. During kernel compilation, you can specify a folder as the root file system when the kernel is started. In Linux, the file system is called initramfs.

Take i386 as an example)

1. Download The Kernel File

Wget http://www.kernel.org/pub/Linux/kernel/v2.6/Linux-2.6.26.tar.bz2

2. decompress the kernel

Bzip2-d linux-2.6.26.tar.bz2generate A linux-2.6.26.tar file, and then

Tar xvf Linux-2.6.26.tar

After decompression, there will be a Linux-2.6.26 folder

3. Prepare a folder for the iniramfs file system.

Create a folder myinitramfs under the Linux-2.6.26 folder

Write a hello world for testing and name it hello. c, as follows:

 
 

  
  
#include <stdio.h> 
  
  
#include <unistd.h> 
  
  
int main(int argc,char *argv[])  
  
  
{  
  
  
int i = 0;  
  
  
while (1) {  
  
  
printf("hello world (%d)\n",i);  
  
  
}  
  
  
 return 0;  
  
  
} 
 
 

Compile gcc-static-o init hello. c

Copy init to the myinitramfs folder.

Cp init myinitramfs/

To display text, you also need to prepare the console device file in the folder.

Mkdir myinitramfs/dev

Cp-a/dev/console myinitramfs/

4. Compile the kernel

Under the Linux-2.6.26 file, execute make help.

You will see a lot of help information, one of which is i386_defconfig

Run make i386_defconfig to generate a. config file.

To add the prepared folder to the Kernel configuration file, you must reconfigure the config file.

 
 

  
  
Make config
  
  
In General Setup ---> 
  
  
Initial RAM filesystem and RAM disk (initramfs/initrd) support (BLK_DEV_INITRD) [Y/n/?]
  
  
Initramfs source file (s) (INITRAMFS_SOURCE) [myinitramfs]
 
 

Enter the prepared folder.

After the configuration is completed, the. config file contains the following definition:

CONFIG_INITRAMFS_SOURCE = "myinitramfs"

Save. config

Make

5. Use qemu to test the kernel and initramfs

Qemu-kernelLinux-2.6.26/arch/i386/boot/bzImage-initrd Linux-2.6.26/usr/initramfs_data.cpio.gz/dev/zero

The initramfs_data.cpio.gz file is automatically generated by the internal kernel, with different domain names. However, the suffix is .cpio.gz.

The Linux root file system is successfully created.

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