Nios II: Building your first kernel

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This page documents the basic steps to configuring, building and testing your first kernel.

Contents

The checklist

Before you get started, ensure you have all of the following:

  • a uClinux-dist tree, with the branch of your choice checked out
  • a Nios II toolchain somewhere on your search path
  • a PTF file to use as the basis for the vendor H/W selection step

make menuconfig

Starting in the top directory of the uClinux-dist tree, run 

$ make menuconfig

and select the following:

  • Vendor/target: Altera/nios2nommu
  • Kernel version: 2.6.x
  • Libc version: None
  • "Default all settings (lose changes)"

Note that it's important to select the Libc version of "None" since we have no need for a C library. And you can see the results of the configuration in the top-level .config file.

vendor_hwselect

Next, do the vendor hardware selection step by running: 

$ make vendor_hwselect SYSPTF=<pathname to your PTF file here>

and answer any questions appropriately.

If you're curious, you can examine the resulting generated makefile with: 

$ cat linux-2.6.x/arch/nios2nommu/hardware.mk
SYSPTF = <PTF filename>
CPU = cpu_0
UPLMEM = cfi_flash_0
EXEMEM = sdram_0
$

Building the kernel

Finally, build the kernel by running: 

$ make

at which point the resulting kernel image should be in the file images/zImage.

The default config file for the 2.6 kernel that will be used for this build can be found at vendors/Altera/nios2nommu/config.linux-2.6.x.

For much more detail, see the Nios wiki page [here] and the wiki page for testing your new image [here].

What's in that initramfs, anyway?

Even if you're building a completely default kernel image, it will still have an embedded initramfs image to be used as the root filesystem. We'll discuss the mechanics of the initramfs creation on a later page but, if you truly want to see the initramfs image contents, you can always gunzip and examine the contents of linux-2.6.x/usr/initramfs_data.cpio.gz once the kernel build is complete.

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