What is kernel zImage?

zImage: a compressed version of the Linux kernel image that is self-extracting. uImage: an image file that has a U-Boot wrapper (installed by the mkimage utility) that includes the OS type and loader information. A very common practice (e.g. the typical Linux kernel Makefile) is to use a zImage file.

What does load kernel mean?

To “load” them means copying them from the boot medium (harddisk, CD, USB stick.) to system RAM.

What is difference between vmlinux and vmlinuz?

The vmlinux is the uncompressed built kernel, vmlinuz is the compressed one, that has been made bootable. (Note both names vmlinux and vmlinuz look same except for last letter z). Generally, you don’t need to worry about vmlinux, it is just an intermediate step.

What is a key difference between a zImage and bzImage kernel image?

The kernel file contains a tiny gzip used to decompress the kernel and boot it. The difference between the two is that the old zImage decompresses the kernel to low-end memory (the first 640K), and the bzImage decompresses the kernel to high-end memory (more than 1M).

How do I extract Vmlinuz?

Extracting the Linux kernel image (vmlinuz) You will be able to find the extract-linux script at /usr/src/linux-headers-$(uname -r)/scripts/extract-vmlinux . You will be able to find the extract-linux script at /usr/src/kernels/$(uname -r)/scripts/extract-vmlinux .

What happens after kernel is loaded?

“When the kernel is loaded, it immediately initializes and configures the computer’s memory and configures the various hardware attached to the system, including all processors, I/O subsystems, and storage devices.

What are the advantages of loadable kernel module?

The advantage of loadable kernel modules is that we do not need to build the entire kernel in order to make any changes to a module. Hence this saves time and spares us from running into issues loading our base kernel itself. Another advantage is that helps us save memory as we only load them when we need to use them.

Can I write my own kernel?

If you are writing your own bootloader for loading a kernel you need to know the overall addressing/interrupts of memory as well as BIOS. Mostly each operating system has specific bootloader for it. There are lots of bootloaders available out there in online market.

Why is it called vmlinuz?

The kernel binary on the original UNIX as developed at Bell Labs was called unix. And because the Linux kernel executable was made into a compressed file and compressed files typically have a z or gz extension on Unix-like systems, the name of the compressed kernel executable became vmlinuz.

What’s the difference between a kernel and a zImage?

In addition to the kernel zImage may also contain the inital file system (initramfs, initrd) the kernel uses to ‘bring up the system’ before the rootfs is mounted. zImage is the actual binary image of the compiled kernel.

What’s the difference between bzImage and a zImage?

bzImage just means Big zImage. zImage can only be a maximum size 512k. Unless the kernel will be that size or smaller after compiling then you need to make it as bzImage. Earlier kernels where quite able to fit in the 512k range but over time many new features have been added and the zImage limits were reach and something new had to be done.

What is the difference between zImage and rootfs?

You can replace it with your own code if you would like MPU to run bare-metal code without OS (like microcontroller). zImage is compressed version of the Linux kernel image that is self-extracting. rootfs is root file system, which contains all applications, libs and in most cases everything, including home folder.

Where do I find bzImage in Linux kernel?

This something is called bzImage, and has been introduced in kernel version 1.3.73. A bzImage is generated by issuing make bzImage from the toplevel Linux source directory. This kind of kernel image boots similarly to the zImage, with a few changes: