1_5.4.3_Root file system_Building the root file system busybox_P

Before building the root file system, compile busybox first.

Check the readme to see if there is any information on how to compile it. There is some introduction about busybox, such as what is busybox.

How to use busybox.

I didn't see any explanation on how to compile. Looking at the install file, I can see that the method of compiling busybox is similar to compiling the Linux kernel, which is to configure first and then compile with make. It should be noted that if you execute make install directly, it will be installed on the PC by default. We need to specify the installation address additionally.

That is, execute the make CONFIG_PREFIX=/path/from/root install after # and install it to the location we specified.

Execute make menuconfig in the busybox directory and perform the configuration first.

We want to compile for embedded systems, so let's configure the cross-compilation compiler first. There is no cross-compilation setting in the busybox configuration item, so let's take a look at the Makefile.

Generally speaking, cross-compiled variables all start with CROSS. Search for CROSS and you will find a CROSS_COMPILE variable.

No option to configure CROSS_COMPILE was found, so we configure it directly here, or we can execute make CROSS_COMPILE=arm-linux-. Both methods are the same, configuring CROSS_COMPILE to arm-linux-.

Then there is a tab completion function, which is not available in busybox by default. We need to set it up so that it will be more convenient to operate busybox in the future. The path to this function is as follows:

Busybox Settings

Busybox Library Tuning

Tab completion

Then, we use two sources of C library, one is glibc and the other is uclibc. When using glibc, there will be a warning message if it is statically linked.

In make menuconfig, set this item to empty, indicating that it is not selected.

After the configuration is complete, you can compile it. Note that you need to use the make option in the install file and change the address to the place you want to download.

Create a 046 folder to store the files after busybox is installed.

Execute the following command in the busybox directory.

make CONFIG_PREFIX=/home/book/Desktop/test/046_first_fs/ install

Check the 046 folder and you will find that there is already a bin directory.

As you can see, they are all links to busybox.

Looking at linuxrc, I see that it is also a link to busybox.